Concept Version: Recommendations for Refractive Surgery

Please note that this is an intial draft / concept version and will be subject to change.

Authors:  Victoria Till, MD; Joukje Wanten, MD; Andreia Rossa, MD, PR; Paolo Vinciguerra, MD; Mario Nubile, MD; Jesper Hjortdal, MD, PR; Liem Trinh, MD; Guy Kleinmann, MD; Georges Kymiones, MD; Sheraz Daya, MD; Ruth Lapid, MD, PHD; Beatrice Cochener, MD, PR; Thomas Kohnen, MD, FEBO, PR 

Authors Affiliations: Please refer to the declarations of interest.

Correspondence: Victoria Till, MD

Background: Refractive errors are the leading cause of correctable visual impairment. Refractive surgery has expanded from a limited set of procedures to a wide range of options that can correct refractive errors and offer spectacle independence. The patient pathway includes selection, diagnostics, treatment planning, and postoperative care.

Objective: To establish evidence-based recommendations by the European Society of Cataract and Refractive Surgeons (ESCRS) to support patients, clinicians and other relevant stakeholders in decisions about refractive surgery management.

Methods: The European Society of Cataract and Refractive Surgeons (ESCRS) developed evidence-based recommendations to guide patients, clinicians, and stakeholders in managing refractive surgery. A multidisciplinary panel followed the GRADE methodology to assess clinical questions and outcomes.

Results: The guideline addresses 52 questions across the patient care pathway. The fundamental key recommendations for each procedure can be found in the specific chapters.

Conclusions: Key recommendations emphasize the necessity of comprehensive pre-operative evaluations, providing informed consent that outlines the benefits and risks of each refractive procedure. These recommendations for refractive surgery detail the optimal range of refractive errors suitable for each procedure, along with expected outcomes and potential complications. The variability in reversibility and effects between corneal and lens-based procedures is highlighted. It is crucial to note that the systematic literature review identified grey zones with limited scientific proof. For these topics expert opinions were required.

Keywords: Refractive surgery, PRK, LASIK, KLEx, Phakic IOL, RLE, ophthalmology, practice guidelines, efficacy, safety, stability, predictability, complications, GRADE, recommendations

ACD: Anterior chamber depth

AGREE II: Appraisal of Guidelines for Research and Evaluation II

ASCRS: American Society of Cataract and Refractive Surgeons

AL: axial length

CDG: Constituting Guideline Development Group

CME: Cystoid Macular Edema

D: Diopter

DED: Dry Eye Disease

DLI: Dysfunctional Lens Index

EDF: Extended Depth of Focus

ESCRS: European Society of Cataract and Refractive Surgeons

FDA: Food and Drug Administration

FLEX: Femtosecond Lenticule Extraction

FS-LASIK: Femtosecond Laser-assisted Laser in situ Keratomileus

GDG: Guideline Development Group

GRADE: Grading of Recommendations Assessment, Development and Evaluation

HOA: Higher Order Aberrations

IFU: Instructions For Use

IOL: Intraocular Lens

IOP: Intraocular Pressure

KLEx: Keratorefractive Lenticule Extraction

KSR: Kleijnen Systematic Reviews Ltd.

LASEK: Laser- epithelial Keratomileusis

LASIK: Laser in situ Keratomileusis

MMC: Mitomycin C

MK-LASIK: Microkeratome Laser in situ Keratomileusis

NSAID: Non-steroidal anti-inflammatory drug

OCT: Optical Coherence Tomography

OSI: Objective Scatter Index

OVD: ophthalmic viscosurgical device

PICO: Patient- Intervention Comparison Outcome

pIOL: Phakic Intraocular Lens

PMMA: Polymethyl methacrylate

PRK: Photorefractive Keratectomy

PROMS: Patient Reported Outcome Measures

PVD: Posterior Vitreous Detachment

ReLEx: Refractive Lenticule Extraction

RLE: Refractive Lens Exchange

SMILE: Small Incision Lenticule Extraction

TBUT: Tear Break-up Time

UBM: Ultrasound Biomicroscopy

UDVA: Uncorrected Distance Visual Acuity

These recommendations offers a comprehensive overview on the expansive field of refractive surgeries. For all recommendations, a grading system is used to establish the level of evidence, which guide ophthalmologists in determining indication and providing information to patients. It is important to note that these guidelines do not possess legally binding authority and therefore will not establish strict rules with absolute thresholds.

The structure of the recommendations is done according to the refractive surgery patient pathway and includes the following sections: definition and description, screening and patient selection, preoperative assessment, perioperative procedures, postoperative care, and complications.

These recommendations focus on the five most validated procedures (Surface ablative procedures, LASIK, KLEX, RLE and Phakic IOLs), which currently represent the most widely applied approaches. While other procedures are available, they fall outside the scope of the present document and will therefore not be discussed. PTK will not be treated as a separate refractive procedure during this document.

This guideline was developed considering the comprehensive quality criteria as described in the Appraisal of Guidelines for Research and Evaluation II (AGREE II) instrument.(Dans and Dans, 2010) The guideline development group (GDG) consisted of 18 ophthalmologists, and the constituting guideline development group (CDG) of two PhD students and a supervising methodologist. All clinical members possessed expertise in refractive surgery management, and they were practicing in Europe and the Middle East to reflect diverse regions. Review questions were formulated according to the PICO framework or similar frameworks as appropriate. Outcome parameters were selected in advance based on importance for decision-making in the clinical setting. Literature searches were performed, using KSR Evidence, the Cochrane Database of Systematic Reviews, MEDLINE, Embase, and Cochrane Central as resources to identify relevant systematic reviews and randomized controlled trials for each review question. The two PhD-students performed selection of the articles supervised by the methodologist. Critical appraisal of available systematic reviews was performed based on the Risk of Bias assessment Tool ROBIS by reviewers at KSR Ltd. (Whiting et al., 2016b) The strength of the relevant evidence was summarized using the GRADE approach.(Neumann et al., 2014) According to the GRADE approach, the evidence is classified as high (++++), moderate (+++), low (++) or very low (+). These classifications are accompanied by a specific formulation of the recommendations, using the wording ‘must’, ‘should’, ‘could’, ‘may’, ‘may not’, and ‘can be considered’. Considering high-level evidence, the term ‘must’ was used in the recommendations of this guideline. In the case of moderate evidence, ‘should’ or ‘could’ were used. For low-graded evidence, ‘could’ or ‘may’ are applicable, and lastly, when there was very low evidence implemented in the recommendations, ‘can be considered’ was used.(Whiting et al., 2016a, Joanna Briggs Institute, 2020 [accessed 20.2.23], Neumann et al., 2014)

Refractive surgery encompasses a spectrum of techniques, aimed at the correction of refractive errors and therefore enabling a certain degree of spectacle or contact lens independence. This guideline gives an overview of the currently most performed refractive surgery procedures. Techniques not included in this overview are considered either obsolete, lacking sufficient evidence to support their efficacy and safety, or still undergoing investigation.

Procedures have been described by using efficacy, predictability, stability and safety as primary outcome measures. Efficacy is defined as the percentage of eyes with uncorrected visual acuity of 20/20 and 20/40. Predictability is defined as the mean standard deviation, and range of postoperative spherical equivalent or the percentage of eyes within ±1.00D and ±0.50D of desired postoperative refractive error, including a table categorizing refractive outcomes. Stability is defined as the number und percentage of eyes with a change in spherical equivalent of manifest refraction ≥1.00D within a specified interval; the recommended minimal interval is 6 months. Safety is the number and percentage of eyes losing two or more lines of best spectacle-corrected visual acuity (BCVA).(Koch et al., 1998)

The outcomes of refractive surgeries are often depending on the initial refractive correction of the patient which needs to be corrected. Definitions: (Nunez et al., 2019)

• Low myopia lower than 3D

• Moderate myopia: 3.0 to 6.0D

• High myopia: higher than 6.0D

• Low hyperopia: lower than 2.0 D

• Moderate hyperopia: 2.0 to 4.0 D

• High hyperopia higher than 4.0 D

Definitions of astigmatism:

• Low astigmatism: lower than 1.5D

• Moderate astigmatism: 1.5 to 3.0D

• High astigmatism: higher than 3.0D

• Myopic / hyperopic / mixed astigmatism

Orientation of astigmatism

• Regular astigmatism

  • With-the-rule astigmatism: Steep axis of the corneal cylinder is vertical or within 30° of the 90° of vertical meridian (60-120°)

  • Against-the-rule astigmatism: Steep axis of the corneal cylinder is horizontal or within 30° of the horizontal meridians (0-30° or 150-180°)

  • Oblique astigmatism: Steep axis of the corneal cylinder is not within 30° of the horizontal or vertical meridians (31-59° and 121-149°)

  • Mixed astigmatism: A combination of myopic and hyperopic cylinders, making it suitable for cross-cylinder ablation.

• Irregular astigmatism

  • Where the two main axes of astigmatism are not symmetric and/or do not lie 90° apart (orthogonal)

  • Irregular or pathological astigmatism treatment is beyond the scope of this guideline.

Surgical decisions should not be based on refraction alone but should consider all the others influencing factors, such as morphological characteristics of the eye including corneal parameters and patient’s expectations and needs.

The eligibility criteria and application limits for refractive surgical procedures are typically defined by specific thresholds of refractive error, rather than by the spherical equivalent (SEQ). This distinction is important, particularly in cases involving compound refractive errors such as myopic astigmatism. In such instances, the total refractive error is generally assessed by considering the full extent of both spherical and cylindrical components, rather than simplifying them into a single SEQ value. This approach ensures more accurate patient selection and treatment planning.(German Society of Ophthalmology and Professional Association of German Ophthalmologists, 2020)

Prior to refractive surgery, patients should be consulted regarding the desired target refraction. This guideline covers the following refractive targets:

• Emmetropia: Emmetropia refers to the condition in which there are no refractive errors present. When the eyes are in an emmetropic state, objects located at infinity are sharply focused on the retina without any need for accommodation. In practice, a refraction ranging between +0.25D and -0.25D is defined as emmetropia. (Langenbucher, 2015)

• Mini-monovision: Mini-monovision refers to the condition where one eye (usually the dominant eye) is targeted for emmetropia while the other eye (usually the non-dominant eye) is targeted for slight myopia ranging between -0.25D and -0.75D in order to increase spectacle independence. (Cochener, 2018)

• Monovision: Monovision refers to the condition when one eye is targeted for distance vision while the other eye is targeted for near vision. The range of diopters for monovision correction may vary according to the specific needs of the patient and discretion of the surgeon. In practice, monovision in general ranges from -1.00D to -2.50D. (Johannsdottir and Stelmach, 2001, AAO PPP Cataract and Anterior Segment Panel and Hoskins Center for Quality Eye Care, 2021 [accessed 2.5.23])

Laser profiles

The photoablation profile for a PRK or LASIK procedure can be based on various approaches. The conventional treatment, which is the most common, uses the Munnerlyn formula to correct refractive errors based on refraction. This can be enhanced by tomographic evaluation, known as topography-guided treatment, or by whole-eye aberrometry, referred to as wavefront-guided treatment.

Wavefront-guided treatments aim to achieve a more optically precise eye by correcting spatially varying refractive errors identified by a wavefront sensor, rather than applying a uniform correction for spherical and cylindrical errors. Optimized profiles, designed to better preserve the cornea’s natural asphericity and improve vision quality, can be integrated into both wavefront- and topography-guided approaches. The transition zone, present in all profiles, improves visual quality and reduces the likelihood of regression. The Munnerlyn formula establishes the relationship between ablation depth and the optical zone, but modern standard ablations, such as wavefront-optimized or aberration-free profiles, induce fewer spherical aberrations compared to traditional Munnerlyn-based treatments. Wavefront-guided ablations may offer superior outcomes in terms of visual recovery and residual cylinder, but visual results and higher-order aberrations are generally comparable between wavefront and topography-guided treatments. All treatments mentioned above integrate ablation targets opting for natural asphericity, called optimized treatments. (German Society of and German Professional Association of, 2024, Durrie et al., 2010, Phusitphoykai et al., 2003)

It is important to mention that these concepts of topography-guided, wavefront guided and wavefront optimized are applicable to LAISK; PRK and surface ablation.(Mastropasqua et al., 2004)

Photorefractive Keratectomy (PRK)

This procedure is used to ablate the corneal stroma to correct refractive errors. After applying topical anesthesia, PRK involves the removal of the corneal epithelium mechanically or chemically with topical alcohol. As a next step the excimer laser is directed onto the anterior stroma and the exposed surface is ablated. The excimer laser operates using an excited dimer (a combination of argon and fluorine) exposed to a high-voltage electric current, producing ultraviolet radiation at a wavelength of 193 nm, which facilitates the photoablation of tissue. Modern excimer lasers utilize small, precise scanning beams that are highly adjustable in terms of profiles, including optical zones and transition zones. These systems are further enhanced by advanced features such as active eye tracking, cyclotorsion compensation, and pupil shift correction, ensuring optimal accuracy and effectiveness. In case of high risk of haze (e.g., enhancement procedures, high myopia, hyperopic patients) intraoperative mitomycin C 0.2mg/ml for 10 to 30 seconds can be used for haze prevention. (Chuck and et al., 2018) Since this procedure does not include the creation of a flap, PRK can sometimes also be used in thinner corneas, leaving more residual corneal stromal tissue, as well as in patients who may be at risk to flap dislocation such as contact sport athletes or military personnel. (Chang and al., 2022)

Transepithelial-PRK, introduced as a variation of the classical PRK procedure in 2007, integrates the epithelial removal using the laser and stromal ablation into a single step. Unlike traditional PRK, where epithelial removal is performed manually or chemically, trans-PRK utilizes the excimer laser to directly remove the corneal epithelium before reshaping the stroma.(Chang and al., 2022, Alasbali, 2022, Hashemi et al., 2022)

In the procedure-specific chapters, PRK and transepithelial-PRK are treated as similar procedures, as differences in the outcomes appear to be minimal and transepithelial-PRK and PRK are regularly treated as one procedure in the literature. These two procedures will not be differentiated in the outcome reports due to the lack of clear evidence demonstrating significant benefits at this time, particularly in terms of pain, corneal haze, and recovery.

Laser-Assisted in Situ Keratomileusis (LASIK)

In LASIK, the patient’s eye is anesthetized with topical anesthesia. A suction ring is then applied to stabilize the cornea and prevent eye movement during surgery. The creation of the corneal flap is achieved with either a conventional mechanical microkeratome or a femtosecond laser. Once the flap is folded back, the underlying corneal stroma is exposed. The laser is directed onto the exposed cornea and the cornea is sculpted using a preprogrammed ablation profile. After the sculpting is complete, the corneal flap is repositioned, and its edges are smoothed without the need for sutures.(Ophthalmology, 2012)

This procedure offers advantages compared to surface photoablation techniques, including less postoperative discomfort, faster visual recovery, and decreased risk of haze, making it the most common procedure for corneal refractive surgery. This procedure combines lamellar corneal surgery with the accuracy of the excimer laser to correct refractive errors. (Chang and al., 2022, German Society of and German Professional Association of, 2024).

Mechanical microkeratome LASIK (MK-LASIK)

Mechanical microkeratome LASIK (MK-LASIK) utilizes an instrument with an oscillating blade to create a corneal flap typically ranging from 90 to 200 micrometers in thickness. Initially, flap-thickness ranged from 180 to 200 micrometer (µm), later reduced to 90 to 120 micrometer (µm) to potentially mitigate the risk of ectasia and dry eye. The microkeratome is attached to the suction ring and cuts through the epithelium, Bowman’s layer, and superficial stroma, stopping at a preset point to create the corneal flap. A hinge is left at one side of the flap in order to be able to fold it back, revealing the corneal stroma. (Xia et al., 2015)

Femtosecond LASIK (FS-LASIK)

Femtosecond laser-assisted LASIK (FS-LASIK) involves a focusable infrared laser that emits ultrashort (10 ^-15 second ⁾ pulses, creating closely spaced spots (bubbles) to photo-disrupt tissue within the corneal stroma. The surgeon lifts the flap by simply separating the areas where the bubbles have formed and folding back the flap. FS-LASIK reduces major complications like irregular flaps or buttonholes compared to MK-LASIK. However, rare complications might include the rainbow effect, attributed to irregular stromal femtosecond cuts and transient light sensitivity, related to levels of energy used. FS-LASIK may offer greater accuracy in flap thickness and homogeneity compared to MK-LASIK, potentially leading to a smaller flap if centered over the optical zone. Moreover, reducing flap thickness can lower the risk of ectasia. Some studies suggest associations with reduced induction of higher order aberrations (HOA), improved contrast sensitivity, longer tear break-up time (TBUT), and more predictable flap thickness compared to MK-LASIK.(Chang and al., 2022, Chuck and et al., 2018)

PresbyLASIK

PresbyLASIK is a laser vision correction technique designed to treat presbyopia by modifying corneal asphericity and creating a multifocal ablation profile, thereby improving the ability to focus at various distances. Several ablation profiles are currently in use, including central PresbyLASIK and peripheral PresbyLASIK, where the near vision profile is applied to the central or peripheral cornea, respectively. The specific approach depends on the laser platform, and the surgeon’s experience and preference.(Fernandez et al., 2023, Vargas-Fragoso and Alio, 2017)

Keratorefractive Lenticule Extraction(KLEx)

Keratorefractive Lenticule Extraction (KLEx) is a concept that involves the creation and extraction of a lenticule, a disc-shaped segment of corneal stroma, using a femtosecond laser only. In KLEx procedures, there is no ablation of the corneal stroma, instead the procedure includes intrastromal dissection and the creation of a refractive lenticule, which is removed after through a small peripheral corneal incision approximately 3mm in size.

KLEx has been introduced as a minimally invasive technique, shown to reduce early postoperative dry eye symptoms and promote corneal nerve regeneration at 3 months postoperatively, although no difference has been observed in the long term. KLEx may offer theoretical biomechanical advantages over LASIK and PRK, as both the Bowman’s membrane and anterior stromal lamellae remain intact following the procedure. However, it is important to note that these potential advantages require further clinical validation. Overall, KLEx has demonstrated visual outcomes comparable to those of LASIK, particularly when compared with conventional ablation profiles, and provides a large effective optical zone. It may also provide benefits such as minimal postoperative pain and discomfort, resulting in high levels of patient satisfaction. Postoperative recovery, however, is strongly influenced by the surgeon’s learning curve and the optimization of the laser energy settings. However, KLEx presents certain limitations. At present, the procedure is primarily available for myopic patients (with or without myopic astigmatism) on most platforms, Moreover, unlike LASIK and PRK, KLEx currently lacks the capacity to correct higher order aberrations. (Ganesh et al., 2018). Recently, hyperopic KLEx has become available with CE marking in Europe.

KLEx has gained recognitions in treatment for myopia and myopic astigmatism, demonstrating predictable and precise outcomes in both visual acuity and visual quality. However, mastering the technique for lenticule extraction requires a learning curve for beginning surgeons. This learning process typically involves observation, wet-lab training, and hands-on experience, with particular emphasis on lamellar dissection and proper handling of the refractive lenticule. Complications are more likely during the early stages of training, most commonly related to challenges in lenticule extraction.(Moshirfar et al., 2024)

Ongoing refinements of the technique, along with advances in cyclotorsion compensation and improved alignment control, continue to enhance procedural outcomes and reduce complications across all levels of surgical experience. The recent incorporation of cyclotorsion compensation has enabled more accurate correction of higher degrees of astigmatism. In addition, the technique is now being explored for the correction of hyperopia. (German Society of and German Professional Association of, 2024)

Definition of "Presence of risk factors for corneal refractive surgery" (Risky cornea)

A risky cornea or better described the presence of risk factors for corneal refactive surgery” is best understood as a multifactorial entity characterized by one or more unfavorable features, including reduced corneal thickness, abnormal curvature patterns, ocular surface disease, and disturbances of the tear film. In such corneas, refractive surgery carries an increased likelihood of intraoperative or postoperative complications, a higher probability of suboptimal visual outcomes, and an elevated risk of refractive surprise. In the presence of a risky cornea or additional risk factors, patients must be comprehensively counseled, with particular emphasis on an individualized and detailed informed consent process that explicitly addresses the increased uncertainty and potential limitations of the procedure.

Phakic intraocular lens implantation

Phakic intraocular lenses (pIOLs) are lenses made of polymethyl methacrylate (PMMA), silicone or polymers that are permanently implanted into the eye and that are used in addition to the natural lens, primarily to correct moderate to high myopia offering a good quality of vision. pIOLs preserve the patient’s accommodative function and induce minimal higher-order aberrations (HOA), contributing to enhanced visual outcomes. pIOLS can correct myopia and hyperopia and astigmatism. This approach is particularly desirable in cases of high ametropia, where laser-based corneal reshaping may compromise corneal biomechanics, and also serves a viable option for patients with structurally risky corneas or when corneal refractive surgery is otherwise contraindicated. For high levels of correction, pIOLs have less impact on quality of vision compared to corneal approaches (Barsam and Allan, 2014, Goes and Delbeke, 2022, Lee et al., 2016)

These lenses can be positioned in the anterior chamber (anterior phakic IOLs, or in the posterior chamber behind the iris but in front of the natural lens (posterior pIOLs) which represents the most popular model nowadays. Anterior pIOLs can further be divided into angle-supported and iris-claw anterior pIOLs. Currently only iris-claw anterior pIOLs and posterior pIOLs are in commercial use.  Angle-supported pIOLs are not implanted due to excessive endothelial cell loss in some patients and increased risk of other irreversible anterior segment complications. Some newer posterior chamber pIOLS have a central port to facilitate the physiologic flow of aqueous humor, thereby eliminating the need for peripheral iridotomies prior or during implantation.(Guell et al., 2010)

Anterior Chamber pIOLs require a deeper anterior chamber of at least 3mm, as well as a perfect conformation of the iris. Peripheral iridotomies using Nd: YAG lasers or intraoperative peripheral iridectomies can be considered for Anterior pIOLs to prevent pupillary block. It has to be mentioned that most modern phakic IOLs come with a central aquaport with no need for iridotomy. Rigid lenses made of PMMA require bigger incisions (5.0mm) needing stitches, while the foldable Iris-claw lenses allow for smaller incisions (3.2mm). (Kohnen and Koch, 2004) Any phakic IOL, especially anterior chamber pIOLs, carries the risk for chronic endothelial cell loss and therefore requires annual check-ups. If endothelial cell loss reaches a threshold of concern, the lens must be explanted. Other complications, which occur more frequently with AC pIOLs, include pupil deformation, decentration, and luxation.

Implantation of posterior chamber pIOLS located behind the lens does not depend on a deep anterior chamber (over 2.8mm is enough). Posterior pIOLs need smaller incisions (2.2mm), than anterior chamber pIOLs.(Kohnen and Koch, 2004) Concerning the posterior chamber pIOL, the expected vaulting goes between 250 and 750 micrometer (µm).  In general, the list of possible complications is similar for anterior and poster chamber phakic IOLs, but in posterior chamber lenses the formation of cataract and pigmentary glaucoma are the main concerns. Both types of phakic IOL implantations might lead to pupil block and pigment dispersion.

Refractive lens exchange

Refractive Lens Exchange (RLE) is a procedure involving the extraction of the natural lens and implantation of an intraocular lens (IOL), additionally correcting a refractive error. The surgical technique for RLE is a variety of the standard cataract surgery, with the key distinction being the absence of visually significant cataract. The primary aim of RLE is to address refractive errors including any ametropia and presbyopia when alternative refractive procedures are deemed inadequate. RLE is particularly used for refractive correction of presbyopic patients and in patients with lens opacity expected to progress quickly. This type of intraocular lens surgery primarily addresses patients seeking spectacle independence, often focusing on advanced technology or high-performance lenses that enhance the range of focus, either partially or fully. Therefore, these lenses can also be considered for patients undergoing cataract surgery, provided they have a normal cornea, ocular surface, and retina.

Commercially available lenses are specifically approved for implantation during cataract surgery and are primarily intended for use in this context. However, unlike cataract surgery, where insurances typically cover part of the cost with a co-payment for the IOL, there is no insurance reimbursement for refractive procedures in most parts of Europe. The availability of various IOL models, as well as different refractive targets, provides patients with a diverse range of options when considering an RLE procedure.(Chuck and et al., 2018, Alió et al., 2014, Kaimbo Wa Kaimbo, 2016)

Refractive lens exchange offers advantages over corneal refractive surgery in selected cases, especially considering some patients with dry eye disease and corneal pathologies. It further eliminates the need for cataract surgery in the future. RLE offers an effective and consistent outcome and postoperative safety. Adequate indication and strict selection as well as the correct IOL calculation are mandatory to achieve this goal. (Alio et al., 2014)

RLE can either be achieved via phacoemulsification of the lens, which involves making a small incision, followed by the insertion of an ultrasonic probe, to break up and aspirate the lens capsule content, or with the support by femtosecond laser-assisted surgery which performs some of the manual aspects of the lens removal procedure. The probe emulsifies and aspirates the lens.(Kelman, 2018) Foldable lenses fit into the small opening (capsulorhexis) created in the anterior lens capsule. Femtosecond Assisted Laser Surgery uses a laser to dissect tissue, creating a corneal incision and performing the capsulotomy and initial lens fragmentation (usually not needed at all in RLE).(Al-Khateeb et al., 2017)

It is important to mention that in addition to the cataract procedural risks, these patients may have an increased risk of retinal detachment. This is especially true for younger, male myopic patients, while patients with severe hyperopia can be at risk of developing choroidal effusion.(Alio et al., 2014) If the patient has a complete PVD (posterior vitreous detachment) and a healthy peripheral retina with no predisposing lesions, the risk for retinal detachment is acceptably low.

Intraocular lenses (IOLs) are implantable devices used to replace the eye’s natural lens, most commonly in the context of cataract or refractive lens exchange surgery. Due to the diversity in design, materials, and visual performance, creating a consistent and comprehensive classification system remains challenging. Therefore, the ESCRS Functional Vision Working Group has developed an evidence-based functional classification for IOLs.(Ribeiro et al., 2024) A more detailed of this functional classification can be found in the ESCRS Cataract Surgery Guideline.

The recommendations for refractive surgery establish well-defined ranges of application for each procedure, delineating the safe and predictable correction limits for myopia, hyperopia, and astigmatism. Importantly, these ranges refer specifically to the spherical and cylindrical components of the refractive error, rather than to the spherical equivalent, since surgical planning must always take into account the steepest meridian. Within these boundaries, reproducible outcomes with high safety margins have consistently been demonstrated.

When determining the upper correction limits, it is not sufficient to consider the spherical and cylindrical values in isolation. Instead, the threshold values must be assessed with respect to the highest refractive change of the principal plane. For example, a correction of +3.0 D sphere combined with –6.0 D cylinder or –3.0 D sphere combined with +6.0 D cylinder falls within the zone of limited application. In contrast, combinations such as 0.0 D sphere with +6.0 D cylinder or +6.0 D sphere with –6.0 D cylinder exceed these limits and therefore lie outside the recommended application range. Other clinically relevant examples include –2.0 D sphere with –5.5 D cylinder (borderline but permissible) versus +5.0 D sphere with +5.0 D cylinder (exceeding the defined range). When evaluating the applicable ranges, it is essential not to rely on the spherical equivalent as a composite measure. Instead, the spherical and cylindrical components must be analysed independently, with each parameter assessed against its respective tolerance limits to ensure an accurate and clinically meaningful determination of applicability.

The recommendations for refractive surgery also recognize that borderline cases inevitably occur. In such scenarios, candidacy cannot be determined solely by the magnitude of the refractive error. Instead, it requires a more nuanced assessment that integrates additional anatomical and technological parameters, including corneal thickness, the anticipated ablation depth, and the performance characteristics of the laser platform employed.

From a biomechanical standpoint, the critical determinant of postoperative safety is not simply the residual stromal bed thickness, but the overall ablation volume in relation to the corneal architecture. Particular caution is warranted in the presence of risk factors such as high astigmatic components, irregular corneal geometry, or a history of chronic eye rubbing, all of which are strongly associated with an increased risk of postoperative ectasia.

In summary, the defined ranges represent the core safety zone for refractive surgery. However, cases at or beyond these margins require individualized decision-making, balancing corneal anatomy, tissue preservation, and laser technology to ensure both efficacy and long-term biomechanical stability.

The zone of application refers to the range within which a given procedure is considered appropriate according to these recommendations. In this zone, the intervention can be expected to achieve reliable and predictable outcomes, and the incidence of adverse events is low. Application within this range is regarded as consistent with current standards of care, provided that the customary requirements for informed consent are fulfilled. This includes comprehensive disclosure of the procedure’s nature, benefits, risks, alternatives, and realistic outcome expectations in accordance with established medical and ethical principles.

The zone of limited application designates the range in which the respective procedure may still be performed; however, outcomes are typically less predictable and are associated with a higher frequency or severity of side effects and complications. Although treatment in this zone is not categorically contraindicated, it requires careful case selection and a particularly stringent risk–benefit assessment. In this context, enhanced informed consent standards apply. Patients must be explicitly informed about the comparatively reduced efficacy, the increased likelihood of adverse effects, and any specific uncertainties related to the intervention in this extended range.

Outside both the zone of application and the zone of limited application, the use of the respective procedure is not recommended. Should a procedure nevertheless be performed beyond the recommended zone of limited application, the informed consent process must explicitly state that the intervention is being undertaken outside the recommended range (German Society of Ophthalmology and German Professional Association of Ophthalmology, 2024).

This chapter serves as a foundational and introduction guide, offering overreaching recommendations applicable to cornea and lens-based procedures in general. Within this chapter, essential principles for decision-making in the refractive surgery care pathway are provided. For more detailed and procedure-specific insights, readers are directed to corresponding chapters where recommendations specific to each refractive surgery technique are presented.

Refractive surgery can be subdivided into cornea-based and lens-based procedures and are all aiming to correct refractive errors to achieve spectacle or contact lens independency, which includes the main goal for patients seeking refractive surgery.

General indications for refractive surgery procedures include a stable refraction (lower than 0.5diopter (D) change over one year), which lies within the specific limits of application for the procedures of interest. (Kohnen et al., 2008) The specific limits of application for each procedure can be found in the procedure-specific chapters.

Please be aware that while it is up to the certified clinician’s judgement taking into account all risk factors and patient characteristics whether to apply a certain refractive surgery technique in a patient, the absolute limit of each laser platform is defined by the laser’s IFU (Instructions For Use). In certain patients, general limits can be discussed and adjusted if recorded in the patients’ files after considering all relevant factors. Deviations from recommendations need to be motivated and recorded in the patient chart.

Limits of application for cornea-based procedures:

• Low to moderate myopia. High myopia (higher than 6 D) can be corrected but specific precautions have to be taken into account, such as characteristics of the cornea and other (ocular) comorbidities, to ensure safety and effectiveness in correcting high myopia through cornea-based procedures.

• PRK, LASIK and KLEx are indicated to correct low to moderate hyperopia.

• Low to high astigmatism can be corrected. Cyclotorsion compensation and perfect alignment is required in case of a cylindrical component of higher than 1.5D.

The laser-platform specific conditions are described in the instructions for use for each device. The surgeon is recommended to follow these instructions. (GRADE +)

Limits of application for lens-based procedures:

• Low to high myopia

• Low to high hyperopia

• Low to high astigmatism

Company product specific conditions are summarized in the instructions for use for each product. The surgeon needs to follow these instructions. Special care is needed in case of high ametropia regarding accuracy of IOL calculation and the impact on quality of vision. (GRADE +)

What are possible surgical recommendations for patients with systemic diseases with ocular risks?

In cases with uncontrolled systemic diseases, performing refractive surgery is contraindicated. In stable cases, refractive surgery may be considered after evaluating the contraindications for the specific procedure. (GRADE +)

In case of cornea-based surgery, special attention has to be given to diabetes and collagen vascular diseases, such as rheumatoid arthritis or dermatological conditions such as psoriasis, eczema, lichen planus, Ehlers Danlos syndrome or fibromyalgia, which may influence recovery or lead to neuropathic pain. (GRADE +)

Refractive surgery should be avoided during pregnancy and breast feeding. (GRADE +)

What ocular risk factors or comorbidities must be taken into consideration before surgery?

In cases with uncontrolled ocular pathologies, performing refractive surgery is contraindicated. In stable cases, refractive surgery may be considered after taking into account the contraindications for the specific procedure. (GRADE +)

Corneal comorbidities, particularly dry eye disease (DED), Meibomian gland disease (MGD), herpes simplex or herpes zoster infection, and Fuchs corneal dystrophy are to be considered as risk factors for cornea-based surgeries requiring specific management. (GRADE +)

How to address patients with DED who are considering refractive surgery? Is there a specific management for DED patients prior to refractive surgery? Is there a specific pretreatment necessary and what leads to deselection?

The tear film, tear production and ocular surface should be evaluated in patients who are considering refractive surgery, since this is one of the relative contra-indications. (GRADE +)

All patients should undergo a thorough slitlamp examination, including dye-tests (?), to assess for ocular surface diseases prior to refractive surgery, with particular attention to those presenting with dry eye symptoms. Both functional symptoms and objective findings should be evaluated. As many asymptomatic patients may reveal ocular surface dysfunction postoperatively, special caution is needed in cases of poorly controlled dry eye syndrome. (GRADE +)

Tear film can be assessed by measuring the tear film break up time (TBUT), performing Schirmer’s test with topical anesthesia, evaluating the lid margins and the Meibomian glands (including gland expression), conducting meibography, and, if available assessing tear osmolarity to quantify the severity of ocular surface disease. (GRADE +)

What are the contraindications for refractive surgery procedures?

General contraindications for cornea-based procedures

Absolute contraindications:

• Uncontrolled systemic diseases: auto-immune disorders, connective tissue diseases, diabetes

• Unstable, uncontrolled or advanced stage of certain ocular diseases (such as glaucoma, inflammatory ocular diseases, and retinal progressive pathologies)

• Presence of progressive cataract

• Presence of progressive corneal diseases and thinning disorders or abnormal corneal topography (forme fruste keratoconus)

• Pregnant or nursing women

Relative contraindications:

• Age lower than 18 years old

• Functional monocularity

• Unstable refraction (higher than 0.5D change over one year) (exceptions might include unstable refraction for certain professional groups (e.g., policemen, military personnel, in certain countries)

• Specific corneal characteristics:

  • Corneal thickness lower than 500 micrometer (µm)

  • Excessively steep corneas (higher than 46D) for moderate to high hyperopic treatments or excessively flat corneas (lower than 38D) for moderate to high myopic treatments

  • Abnormal corneal topography

  • Corneal dystrophies

• History of herpes simplex or herpes zoster keratitis

• History of uveitis

• Pregnant or nursing women

• Uncontrolled ocular surface disease

• Unrealistic patient expectation

Concerning the relative contraindications for corneal procedures it has to be mentioned that the risk for ectasia does not exclusively rely on the residual stromal thickness but is among others highly dependent on the patients’ age, preoperative pachymetry, corneal topography, the percentage of tissue and viscoelasticity altered, the percentage of stromal subtraction as well as the amount of refractive error to be corrected. (GRADE +)

The clinical refractive range of indications depends on features of the individual patient: morphology of the cornea, pupil size that will influence the limits and therefore the specific refractive indications. (GRADE +)

General contraindications for lens-based procedures

Absolute contraindications:

• Uncontrolled systemic diseases: auto-immune disorders, connective tissue diseases, diabetes

• Unstable or advanced stage of certain ocular diseases: glaucoma, retinal detachment or macular degeneration

• Active ocular inflammation

Relative contraindications:

• Unstable or untreated external eye diseases

• Unstable refraction (higher than 0.5D change over one year) (only true for phakic IOLS, not for RLE)

• Severe and uncontrolled dry eye disease (DED)

• Unrealistic patient expectations

• Presence of progressive cataract (when considering phakic IOL implantation, not true for RLE)

The procedure-specific indications and contraindications can be found in the procedure-specific chapters.

How should shared consent be obtained in patients who want to undergo refractive surgery? What information should be given to patients prior to surgery and how detailed should this information be? (Questions [include numbers from big document])

Proper screening of the patients as well as setting realistic expectations is mandatory prior to refractive surgery. (GRADE +)

Patients should be informed about the course of the procedure, possible complications, alternatives to the procedure, occurrence of aging of the lens leading to presbyopia in the fourties, postoperative treatment as well as postoperative desired behavior. (GRADE +)

Informed consent might be achieved in multiple formats (verbal discussion, videos, written form), but depending on the country’s legal requirements a written consent may be mandatory. The patient should receive a reflection period after receiving all information before signing informed consent. (GRADE +)

The patient and ophthalmologist should take the shared decision for surgery and be well-documented in the patient's medical records. (GRADE +)

Preoperative informed consent must be achieved by an ophthalmologist and should be documented. (GRADE +)

The informed consent should minimally include:

• Indication and limits of the procedure

• Detailed description of the process of the procedure

• Potential risk factors

• Preoperative assessment

• Potential adverse events and serious adverse events

• Mid- and long-term expected outcomes

• Postoperative desired behavior

• Postoperative medications

• In specific cases: possibility of intraoperative change of surgical method

• Alternative surgical and non-surgical methods to achieve the desired goal

In cases where elevated risk factors are present, the informed consent process must be conducted with particular rigor. Patients should be provided with a more extensive discussion of the specific risks relevant to their individual condition, ensuring that both common and less frequent complications are clearly addressed. In addition to the verbal explanation, these risk factors must also be explicitly documented and presented in written form within the informed consent document, thereby reinforcing patient understanding and supporting ethical and legal standards of care.

What has to be included in the preoperative check-up? (Questions [include numbers from big document])

Patient selection via a preoperative assessment of the patients’ expectations, risk factors and medical history must be performed during a preoperative check-up. (GRADE +)

 On indication of suspicious cases, additional glaucoma or retinal assessment must be performed. (GRADE +)

Which standard operating procedure should be applied in time (i.e., when) and in which way (i.e., how) to a patient who has undergone a refractive surgery procedure? (Questions [include numbers from big document])

Check-up appointments should be continued until the operated eye has reached a stable situation. (GRADE +)

Patients should seek help if they experience a decrease in vision following an initial improvement, increased pain, sensitivity to light, foreign body sensation or redness, and/or the sudden onset of black dots or flashing lights. (GRADE +)

After surgery, patients should adhere to medical guidance to prevent infection, including avoiding exposure to dust, trauma, tap water, and swimming pools. To promote proper healing, they should also refrain from rubbing the eye, engaging in contact sports, heavy lifting, and using eye make-up until recovery is complete—typically within 1 to 2 weeks, depending on the procedure. Patients must also wait for legal clearance before resuming driving. (GRADE +)

Cornea-based procedures

Patients are instructed to follow a strict eye drop regimen after corneal laser procedures, including antibiotics, corticosteroids and for specific indications NSAIDs. The specific regimen may differ depending on the procedure (Surface ablation, LASIK, or KLEx). In general the following drops are used: antibiotics, corticosteroids, lubricants. Antibiotic drops are used during the early postoperative period. NSAIDs can be applied in the early postoperative period for pain management, but prolonged use should be avoided as it may impair wound healing, especially in epithelium off procedures. Additionally, low-grade topical corticosteroids are recommended after epithelial regrowth for wound healing modulation. Furthermore, artificial tears are often prescribed to lubricate the eye after surgery.(GRADE+)

A check-up during the first week after surgery is recommended to confirm epithelial healing assess stability, and evaluate interface transparency in cases of lamellar surgery. (GRADE +)

Oral NSAIDs or analgesics can reduce postoperative pain as well as a bandage contact lens which is commonly used during the first days. However, patients should be monitored for an increased risk of infection with the bandage contact lens. (GRADE +).

Postoperative follow-up visits should include assessment of the corrected and uncorrected visual acuity, including refraction assessment, keratometry, corneal topography or tomography, and slit lamp examination. Optional assessments include tonometry, funduscopic exam, specular microscopy, meibography, epithelial mapping, and optical coherence tomography (posterior segment). (GRADE +)

Patients should inform their surgeon of any prior corneal refractive surgery when developing cataracts, as this requires special attention during IOL power calculation. Additionally, younger patients who have undergone refractive surgery will eventually develop age‑related presbyopia and require near‑vision glasses. (GRADE +)

Lens-based procedures

Following pIOL implantation, a check-up on the day of surgery or during the first postoperative day is recommended to assess the intraocular pressure (IOP) and the inflammation status of the eye. (GRADE +)

Following RLE a follow-up visit should be considered between 1 week and 2 weeks after surgery. (GRADE +)

Postoperative follow-up should include assessment of uncorrected and corrected visual acuity, refraction, intraocular pressure, slit-lamp examination (with attention to anterior chamber depth, IOL centration, and pupil reactivity), and a funduscopic examination. In patients with pIOLs, additional evaluations should include gonioscopy, measurement of the pIOL vault, and specular microscopy. An annual check-up is mandatory after pIOL implantation. Corneal topography or tomography may be performed as optional assessment. (GRADE +)

During the early postoperative period following lens-based procedures, antibiotic eye drops, corticosteroid drops, and lubricants should be applied after RLE and pIOL implantation. NSAID drops can be considered after pIOL implantation. Antibiotics can also be applied intraoperatively and can be omitted postoperatively. (GRADE +)

Cornea-based procedures

The complaints during the early postoperative period differ for each procedure:

• Surface ablative procedures (PRK): patients typically may experience pain and discomfort during the first days postoperatively, along with blurry vision. These symptoms diminish gradually as the corneal epithelium heals and visual acuity improves over time. Mild dry eye symptoms can be present during the first weeks to months after surgery.
• Intrastromal refractive procedures (LASIK, KLEx): patients may commonly experience slight discomfort, blurry or fluctuating vision during the first hours or few days; mild dry eyes symptoms can be present for longer period after surgery (weeks to months, especially after LASIK).
• All cornea-based procedures: halos and glare, especially at night, are commonly reported in the first 1 to 3 months following surgery.

Lens-based procedures

After intraocular surgeries patients may experience mild discomfort in the eye (foreign body sensation or grittiness) and blurred vision, which will improve as the eye heals and especially with the recovery of the normal ocular surface.

What are the most common (serious) adverse events during and after refractive surgery procedures? (Questions [include numbers from big document])

In general, both corneal- and lens-based procedures demonstrate a high safety profile, with a correspondingly low incidence of complications. These complications can be categorized into two main groups: intraoperative and postoperative, based on their time of onset.

It is essential to distinguish objective complications from subjective symptoms. Subjective symptoms may be associated with specific complications or occur independently, even in cases of uncomplicated surgery, and may persist for variable durations. Objective complications refer to measurable clinical findings resulting from deviations from an uneventful intraoperative or postoperative course. In contrast, ‘subjective symptoms’ are patient-reported and not necessarily indicative of complications.

Patients should be aware that the typical postoperative course may include transient symptoms such as pain, corneal and lid edema, dryness of the eye, and fluctuations in visual acuity. These symptoms are not classified as complications unless they persist beyond three months. True complications, on the other hand, include persistent dry eye, loss in best corrected visual acuity, dysphotopsia, pronounced halos and glare, impaired night vision, and diplopia. It is crucial to counsel patients on the possibility of these complications and their potential impact on postoperative outcomes for each procedure.

Objective complications of cornea-based procedures

Intraoperative complications

Complications that occur during laser-based procedures can be general or technique-specific. The most common include: (Tse et al., 2016, Sahay et al., 2021) (Asif et al., 2020) (Ivarsen et al., 2014) (Krueger and Meister, 2018)

• Decentered corrections (Surface ablation procedures, LASIK or KLEx). Decentered corrections may result in suboptimal optical zones, leading to postoperative reduced uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and overall visual quality. Patients may experience symptoms such as halos and glare or diplopia.

Suction loss (LASIK and KLEx). Loss of suction from the vacuum system that stabilizes the globe-device contact can result in incomplete flap creation or incomplete lenticule, cap, or side-cut formation. This may prevent the procedure from being completed in the same session. Depending on the case, refractive correction can either be completed during the same session or postponed. Subsequent correction may involve the same or an alternative technique.

• Sub-optimal femtosecond laser dissection, as seen in procedures like FS-LASIK and KLEx, can result in issues such as dark spots of non-dissection, opaque bubble layers, or vertical gas breakthrough. These complications may cause difficulties in flap opening or lenticule extraction and, in some cases, prevent the procedure from being completed in the same session. Flap-related complications (LASIK), include inadequate flap cutting, free caps, flap ruptures, or buttonholes, and can occur during the flap creation phase or become evident during manipulation. Such issues may result in suboptimal outcomes and could necessitate additional corrective procedures. In KLEx, abnormal lenticule dissection and extraction may arise due to cap or incision laceration, stromal dissection in the wrong plane, or incomplete lenticule extraction, leaving a remnant portion of the lenticule. These complications can lead to suboptimal visual outcomes and may require further interventions or corrective procedures.

Postoperative complications

Postoperative complications generally manifest at varying intervals after surgery. These complications may be directly linked to intraoperative events, influenced by patient-specific factors or behaviors, or occur independently. While some are common, transient, and cause minimal disruption to quality of life, rarer complications can have a more profound effect, impairing visual function, causing significant symptoms, and negatively impacting overall quality of life. Among the relevant postoperative complications, the following are included:

• Under- or over-Correction: This may occur due to discrepancies between predicted and actual healing after surgery, loss of best corrected distance visual acuity due to intraoperative complications, or from suboptimal stromal tissue ablation during the procedure, unrelated to complications or laser malfunction. It should not be considered a complication unless the residual refractive error is significant in relation to the original refractive state. Evaluation should take place at the end of the wound healing phase before considering refractive enhancement procedures.(Naderi et al., 2018, Taneri et al., 2021)
• Dry Eye Symptoms (Surface Ablation, LASIK, KLEx): These symptoms can vary in severity and duration and are typically caused by transient changes in corneal innervation due to the surgical procedure. Pre-existing ocular conditions may predispose patients to more severe symptoms. (Cohen and Spierer, 2018) (Kobashi et al., 2017, Asif et al., 2020) (Wang et al., 2017) (Shen et al., 2016, Cai et al., 2017)
• Alterations in Stromal Transparency and Regularity (Surface Ablation, LASIK, KLEx): Excessive wound healing responses, such as persistent stromal haze after PRK, or acute inflammatory factors and infections, can lead to changes in stromal transparency and regularity. (Tomás-Juan et al., 2015) (Chan et al., 2016)
• Infectious keratitis (Surface Ablation, LASIK, KLEx): Most infections occur within a week of the procedure, but sometimes infections might occur even after a month. Infections after LASIK and KLEx occur most frequently, but not exclusively, in the stromal interface. Keratitis after Laser refractive surgery can delay visual recovery. Keratitis might be non-infectious as in diffuse lamellar keratitis or central toxic keratopathy, occurring frequently during the first few days after LASIK and KLEx. Both infectious and non-infectious keratitis occasionally can be induced years after the surgery by an infective or traumatic insult.(Das et al., 2020)
• Flap folds: Flap striae or flap folds can be best described as small wrinkles in cornea after LASIK surgery. Flap folds mostly occur due to uneven alignment of the flap edge with the epithelial ring. Microstriae are mostly asymptomatic, while full thickness folds might lead to visual impairment. Bowman’s and cap folds or distortions can occur, similarly, after KLEx surgery. In KLEx, microstriae might appear secondary to epitheliopathy, interface debris, and fibrosis at the KLEx incision (Moshirfar et al., 2023). Flap striae can be treated via lifting the flap, removing the remnant epithelium on the surface followed by irrigation. Persistent stria may lead to astigmatism (Moshirfar et al., 2023).
• Epithelial Ingrowth (LASIK, KLEx): In the stromal interface, epithelial ingrowth can lead to irregular astigmatism and a loss of interface transparency, negatively affecting visual quality. If significant symptoms develop, surgical removal of the abnormal epithelial sheet may be required. (Ting et al., 2018) (Asif et al., 2020) (Sahay et al., 2021) (Kamiya et al., 2020)
• Corneal Ectasia (Surface Ablation, LASIK, KLEx): Any corneal subtractive procedure carries the risk of progressive corneal ectasia. This may result from misdiagnosed preoperative corneal abnormalities (e.g., form fruste keratoconus) or excessive weakening of the corneal stroma, which depends on preoperative corneal characteristics (thickness, profile, curvature) and the amount of tissue removed to treat the refractive error. (Giri and Azar, 2017) (Moshirfar et al., 2021) (Krueger and Meister, 2018, Moshirfar et al., 2017)
• Flap dislocation (LASIK) : flap dislocation may occur due to inproper replacing of flap during operative procedure or in the early post-operative period due to mechanical forces. Late traumatic flap dislocations have been described. Dislocated flaps should be rinsed and replaced or sutured.

Objective complications of lens-based procedures

Intraoperative complications

Complications that occur during intraocular procedures can be general or technique- specific. The most common include: (Henderson et al., 2014, Zare et al., 2009) (Lundström et al., 2020) (Schallhorn et al., 2019) (Foster et al., 2021)

• Iris damage (pIOL, RLE). Damage to the iris can result in haemorrhages, pupillary irregularities and permanent mydriasis, which influences the visual function and appearance of the patient.
• Posterior capsule rupture with/without vitreous loss (RLE). Posterior capsule rupture can lead to suboptimal visual acuity outcomes, with the presence or absence of vitreous loss playing a significant role in determining the severity and management of the complication. The impact on visual outcomes may vary depending on whether vitreous prolapse occurs and how the rupture is addressed during surgery.
• Dropped nucleus (RLE). Dropped nucleus is a rare complication and might be caused by zonular weakness or by the intraoperative procedure itself and necessitates a posterior vitrectomy. When capsular bag stability is compromised, presbyopic IOLs are no longer suitable and must be replaced with an appropriate monofocal IOL. Patients should be informed of this possibility prior to surgery.

Postoperative complications

Postoperative complications generally manifest at varying intervals after surgery and are different between procedure.

Complications after pIOL implantation

Complications following pIOL implantation can differ depending on the type of IOL used, with iris-fixated, angle-fixated, and posterior chamber IOLs presenting distinct complication profiles. Angle-supported pIOLs have been withdrawn from the market due to concerns regarding accelerated endothelial cell loss, and patients with these implants should be monitored closely. The most important postoperative complications can be subdivided based on the time period they occur: (Kohnen et al., 2010)

• Elevated intraocular pressure. This condition may arise due to several factors, such as pupillary block, inflammation, or the use of viscoelastic materials (OVD) during surgery. Elevated IOP needs to be closely monitored, as it can lead to optic nerve damage and vision loss if left untreated. Early detection and management are crucial to prevent long-term complications. (Galvis et al., 2017)
• Endothelial cell loss. Damage to the corneal endothelial cells can lead to corneal edema. Anterior chamber IOLs generally but not exclusively induce corneal endothelial cell loss. Symptoms of corneal endothelial cell loss are a cloudy cornea, resulting in decreased visual acuity. (Jonker et al., 2018)
• Cataract formation. The location of the phakic IOL as well as the alteration of the aqueous humor and vault predispose the crystalline lens and the pIOL to come into contact, which might lead to the formation of anterior subcapsular cataract. This is more common but not e(Deshpande et al., 2020)

After pIOL implantation it is mandatory to conduct annual follow-ups for these patients, including specular microscopy for AC pIOLS (not for PC pIOLS). IOP measurement, and intraocular imaging such as anterior segment OCT. Patients must be informed that a pIOL will remain in place only until cataracts develop, or other intraocular changes induced by the ppIOL occur.

Complications after RLE

Postoperative complications after RLE are similar to those seen in regular cataract surgery but occur in patients without cataracts. RLE is typically an elective procedure performed in patients with higher refractive errors or presbyopia who seek spectacle independence. These patients may have higher expectations compared to the general cataract population. Important postoperative complications include:

• Retinal detachment. Retinal detachment is a serious complication that can occur after RLE, particularly in patients with risk factors such as high myopia, high axial length, young age (under 50 years) - especially when natural posterior vitreous detachment (PVD) is incomplete - Caucasian ethnicity, and peripheral retinal degeneration. Additionally, Nd:YAG capsulotomy can increase the risk of retinal detachment. Patients with hyperopia generally have a lower risk of retinal detachment, and younger hyperopic patients undergoing RLE tend to face fewer concerns about this complication.(Kook et al., 2008, Nanavaty and Daya, 2012)
• Cystoid Macular Edema (CME). CME involves macular thickening due to a breakdown of the blood-retinal barrier, leading to increased permeability in the perifoveal capillaries and subsequent capillary leakage. This can result in visual impairment, including reduced central vision and visual distortion. Management typically involves topical anti-inflammatory medications, and in some cases, intravitreal injections may be required for severe cases.(Scholl et al., 2011)
• Endophthalmitis is a severe intraocular infection most commonly caused by Staphylococcus epidermidis. This rare but serious condition is associated with factors such as posterior capsule rupture, the need for an anterior vitrectomy, and the use of topical anesthesia. Additional risk factors include older age and male gender. Prompt treatment with antibiotics and, in some cases, surgical intervention is critical to preventing vision loss.(American Academy of Ophthalmology Preferred Practice Pattern Cataract and Anterior Segment Committee, 2021, Lemley and Han, 2007)
• Posterior capsular opacification. PCO is a common complication after RLE, caused by the migration and proliferation of residual epithelial cells onto the posterior capsule. This leads to opacification, impairing visual clarity and contrast sensitivity. PCO can significantly reduce visual acuity and may require a Nd:YAG capsulotomy to restore vision.(Schallhorn et al., 2019) (Nanavaty and Daya, 2012) PCO tends to occur earlier in younger patients and in those implanted with presbyopic IOLs, where the impact on visual quality is perceived sooner due to capsular fibrosis. However, Nd:YAG capsulotomy should not be performed too early, as this increases the risk of cystoid macular oedema (CME), and should only be considered once PCO is confirmed as the cause of reduced visual outcomes.

What are the indications and contraindications for corneal surface ablative procedures?(Question [include number from big document])

Limits of application PRK and Transepithelial-PRK:

• Myopia lower than 6.0D with or without astigmatism lower than 4.0D. (GRADE +)
• Myopia higher than 6.00D only after further evaluation of risk factors as well as different morphological aspects, corneal tissue and the optical zone
• Hyperopia lower than 3.00D with or without astigmatism lower than 4.0D. In this group of patients an increased complication risk, including haze development have to be considered. (GRADE +)

These limits of application must take into account a minimal preoperative corneal thickness of 480 micrometer (µm), and the percentage of tissue ablation (PTA) should not exceed 40 percent. (GRADE +)

It is mandatory to regard the different laser system approvals (CE-markings) which include the ranges of indication for specific devices.

In cases of higher ametropia, special attention should be given to sufficient corneal thickness according to ablation depth and residual estimated corneal thickness. Additionally, other critical factors such as corneal symmetry, regularity, stability of ametropia, associated cylindrical components, and history of eye rubbing should also be evaluated. (GRADE +)

Efficacy

What is the efficacy of PRK/Trans-PRK? (Question [include number from big document])

Surface ablation is effective for correcting low to moderate myopia (lower than -6.0D) with or without astigmatism (lower than -4.0D). The evidence for surface ablation correcting for high myopia (higher than 6.0D) and astigmatism (higher than -3.0D) is limited. (GRADE +/++)

The evidence considering the efficacy of surface ablation for hyperopia (lower than 3.0D) is limited. (GRADE +)

Surface ablation is comparable to other refractive surgery procedures. Although the evidence is highly heterogenic, no statistically significant differences were found in terms of efficacy between surface ablation and other corneal laser refractive surgery procedures. (GRADE +)

Predictability

What is the predictability of PRK/Trans-PRK? (Question [include number from big document])

Surface ablation has a high predictability when correcting low to moderate myopia (lower than -6.0D) with or without astigmatism (lower than 4.0D). Evidence shows that the predictability in high myopia (higher than 6.0D) and astigmatism (higher than 4.0D) significantly lower. (GRADE +)

The evidence considering the predictability of surface ablation for hyperopia (lower than 3.0D) is limited. (GRADE +)

Although discrepancies are found in the literature, surface ablation procedures seem to have comparable results in terms of predictability when compared to other corneal laser refractive surgeries in myopic patients with or without corneal astigmatism. (GRADE +/+++)

Transepithelial PRK offers the main advantage over conventional PRK by utilizing the epithelium as a resurfacing agent, allowing for better management of abnormal and irregular topographic patterns. It is particularly recommended to use T-PRK in combination with a PTK target and followed by a topography-guided photoablation. (GRADE +)

Stability

What is the stability of PRK/Trans-PRK? (Question [include number from big document])

After 12 months, the refractive results of PRK and Trans-PRK are considered stable for low to moderate myopia. (GRADE +)

Performing PRK in hyperopic patients is exceptional since this requires larger de-epithelization with a longer recovery, more regression and more occurrence of haze. (GRADE +)

Safety

What is the safety of PRK/Trans-PRK? (Question [include number from big document])

Surface ablation is safe for correcting low to moderate myopia (lower than 6.0D) and/or astigmatism (lower than 3.0D). The evidence for surface ablation correcting higher degrees of myopia (higher than 6.0D) and astigmatism (higher than 3.0D) is limited. (GRADE +/++)

Limited evidence is available regarding the safety of surface ablation in hyperopia (lower than 3.0D). (GRADE +/++)

Surface ablative procedures are comparable to other refractive surgery procedures in terms of safety, but the risk for ectasia seems to be less after surface ablation compared with corneal intrastromal refractive procedures. (LASIK and intrastromal lenticular surgery) (GRADE +/++)

PRK and Trans-PRK should be preferred over LASIK in patients with pre-existing DED, as these procedures show less induced and lasting dryness, as well as less increase of preoperative ocular surface disease. In case of low risk for ectasia, PRK can be considered, when LASIK and KLEx are deemed unsuitable on a case‑by‑case basis. (GRADE +)

Is the intraoperative use of mitomycin C during PRK to reduce postoperative scar/ haze formation indicated in all patients? Are there any side effects or contraindications one must take into account? How long should mitomycin C be used? (Question [include number from big document])

The application of mitomycin C (MMC) is generally not recommended for primary, normal surface ablation cases. However, its use may be considered in certain situations, such as in cases of resistant haze or when there is a higher risk of haze formation, including after refractive keratectomy, in hyperopic patients, or in patients with moderate to high myopia (higher than -3.0D), and after lenticular surgery. In cases of resistant haze (i.e., persistent after 12–18 months of wound healing and unresponsive to topical steroids), MMC may be used, often in combination with PTK, to facilitate the removal of the opacity. (GRADE+)

Short-time application of MMC 0.02% for 12-20 seconds is safe and effective in preventing haze formation in eyes which underwent surface ablation with an ablation depth above 50-65 micrometers (µm). (GRADE +)
It is also important to note that UV exposure poses a high risk for dense haze formation after MMC application. As a precaution, patients are advised to wear sunglasses for one year to protect their eyes from UV light and reduce the risk. (GRADE +)

There seems to be little difference in haze formation and visual outcome between lower dose of MMC (0.01%) and standard dose (0.02%). Standard dose may be more protective in case of high myopia or deep ablation depths. (GRADE +)

PRK is the pioneer procedure concerning efficacy, predictability and safety. Key indications include low to moderate myopia with or without astigmatism as well as enhancement procedures. Currently it is most discussed in the case of exclusion of LASIK or KLEx. The refinement of energy delivery has allowed the extension of indications with less regression and haze occurring as well as allowing better centration by using the eye tracker and cyclotorsion compensation. Key complications include haze, regression, remaining refractive error ocular surface disease as well as ectasia. MMC has found a place for prevention or modulation of haze.

Experts have observed that PRK and Transepithelial-PRK may be considered safer than LASIK in terms of ectasia risk. However, extensive research is needed to further evaluate the ectasia rates associated with different procedures. While Trans-PRK has been reported to cause less pain and facilitate faster recovery in some case studies, these findings necessitate further validation through comprehensive research.

Additionally, the consideration of combined crosslinking to enable PRK on high-risk corneas presents a potential avenue for treatment, yet the evidence supporting the efficacy and safety of such combined procedures remains scant. For the purpose of smoothing irregular corneas and performing custom ablation, PRK emerges as a viable option, but again, more robust evidence is required to substantiate its effectiveness in these specific applications.

The role of corneal crosslinking prior to laser refractive surgery procedures for preventing corneal ectasia is still unknown. The evidence about the (long-term) safety and efficacy of corneal crosslinking in addition to laser refractive surgery procedures is limited. The reported follow-up is insufficient to confidently assess stability, especially given the potential for ectasia to develop years after surgery. Attention has to be given to possible progressive flattening after corneal crosslinking, which might affect long-term refractive stability as well as the potential risk of infection and fibrosis that may be induced by crosslinking. 

What are the indications and contraindications for intracorneal ablative procedures (LASIK)? (Question [include number from big document])

Limits of application LASIK:

• Myopia lower than 8.0D can be considered. However, it must be noted that the quality of vision will be more affected over 7.0D. (GRADE +)
• Myopia higher than 8.00D only in case of a regular cornea, without any risk factors, and a sufficient corneal thickness (higher than 500 micrometer (µm)) taking flap thickness and ablation depth and residual estimated thickness into account. (GRADE +)
• Astigmatism lower than 4.0D, if the cylinder is greater than the sphere and of the opposite sign. Surgeons must be aware of potential suboptimal results and prolonged recovery when the cylindrical component exceeds the spherical component. (GRADE +)
• Optimal results might be achieved for patients with hyperopia up to lower than +3.0D with or without astigmatism lower than 3.0D after considering risk factors as well as different morphological aspects, corneal tissue and the optical zone. (GRADE +)
• In patients with higher degree of hyperopia (higher than 3.0D), an increased complication risk, including reduced quality of vision, reduced stability and a higher risk of decentration has to be considered. (GRADE +)

It is mandatory to regard the different laser system approvals (CE-markings) which include the ranges of indication for specific devices. (GRADE +)

In cases of higher ametropia, special attention should be given to sufficient corneal thickness according to ablation depth and residual estimated corneal thickness. (GRADE +)

The limits of application must incorporate corneal safety parameters, including a minimum preoperative corneal thickness of at least 480 µm in the absence of additional risk factors, with a recommended threshold of 500 µm or greater. For the residual stromal bed, an absolute lower limit of 250 µm is required, while preservation of 300 µm or more is considered optimal. It must be emphasized that, in any form of corneal subtractive surgery, the decisive determinant of biomechanical stability is not corneal thickness alone, but rather the total ablation volume in relation to the overall corneal architecture. (GRADE +)

It is important to note that the above-mentioned limits strongly depend on different laser platforms, understanding of corneal shape and zone size, and other variables. Additionally, the volume of ablation should be considered as a key factor, rather than focusing solely on the residual posterior stromal bed. (GRADE +)

Efficacy

What is the efficacy of intracorneal ablative procedures (LASIK)? (Question [include number from big document])

LASIK is effective for correcting low to moderate myopia (lower than 6.0D) with/without astigmatism (lower than 2.0D). (GRADE +)

Limited evidence shows that LASIK is effective for correcting high myopia (higher than -6.0D) with/without astigmatism (lower than 5.0D). (GRADE +)

LASIK is effective for correcting low to moderate hyperopia (lower than 3.0D) with/without astigmatism (lower than 2.0D). Lower level of efficacy is reported for correction of high hyperopia (higher than 3.0D). (GRADE +)

LASIK is comparable to surface ablative procedures in terms of efficacy. (GRADE +)

LASIK is comparable to lenticule extraction in terms of efficacy for correcting myopia and low to moderate astigmatism. (GRADE +)

Predictability

What is the predictability of intracorneal ablative procedures (LASIK)? (Question [include number from big document])

LASIK shows comparable results in terms of predictability when compared to other corneal laser refractive surgeries in myopic patients with or without corneal astigmatism. (GRADE +)

LASIK shows high predictability in low to moderate myopia (lower than 6.0D) and low to moderate hyperopia (lower than 3.0D), with astigmatism (lower than 2.0D) (GRADE +)

Predictability is high in MK-LASIK and FS-LASIK with an equal number of patients achieving 0.5D within the target refraction in both groups. (GRADE ++)

Stability

What is the stability of intracorneal ablative procedures (LASIK)? (Question [include number from big document])

The refractive results of LASIK are considered stable for low to moderate myopia. (GRADE +)

Stability of LASIK decreases as the degree of myopia increases. (GRADE +)

For the stability of LASIK among hyperopic patients, the evidence is limited, but stability in general decreases as the degree of hyperopia increases. (GRADE +)

Safety

What is the safety of intracorneal ablative procedures (LASIK)? (Question [include number from big document])

LASIK can be considered safe for treating myopia and hyperopia, with a very low rate of serious adverse events occurring intra- and postoperatively. Note that this highly depends on the amount of preoperative refractive error. (GRADE +)

No statistically significant difference has been found between different refractive procedures including LASIK, PRK and Trans-PRK concerning safety. (GRADE +)

PRK/Trans-PRK and LASEK show less risk for ectasia development than eyes treated with LASIK, which is also the case for KLEx. (GRADE +)

The higher refractive errors, especially high hyperopia still presents an increased complications profile, and one should take into account the reduced safety profile prior to treating patients with hyperopia higher than 3 D. (GRADE +)

Efficacy, safety and predictability of LASIK have been well demonstrated, and LASIK remains the most performed procedure with an access to all ametropia and presbyopia and faster recovery than in PRK and Trans-PRK.

Efficacy, predictability, stability and safety of LASIK are high in the range of low to moderate myopic, hyperopic and astigmatic refractive error. For higher ranges of corrections (within the indication values) specific considerations for corneal morphology and patient’s characteristics and risk factors should be considered. Corneal regularity, symmetry, viscoelasticity and pachymetry should be assessed prior to the procedure. 

The use of newer generation laser systems is advisable as it is correlated with better clinical and refractive results. The use of femtosecond laser for flap creation is, similarly, advisable because it is associated with less intraoperative flap-related complications and better accuracy of flap thickness and homogeneity.

Key complications include dry eye and ectasia. In the case of need of an enhancement procedure, corneal compatibilities for a new ablation have to be checked. Options include re-lift and creating a new flap or surface ablation commonly combined with mitomycin C.

Regarding LASIK, there are several areas which still present unique challenges and considerations due to limited evidence. It must be mentioned that docking with a suction device is more challenging in patients with hyperopic eyes because of their smaller size and generally larger angle kappa. Such special considerations are often required in specific cases to adequately address these challenges.

The benefits of LASIK combined with crosslinking to reinforce the corneal biomechanics is still being debated. While refinements in flap edges and the development of thinner flaps have significantly decreased the incidence of ectasia, long-term follow-up and the establishment of an ectasia registry are still necessary to provide objective insights.

Moreover, the comparative benefits of topography-guided ablation versus wavefront-ablation are yet to be clearly established, indicating the need for further research to demonstrate their relative efficacy.

Higher refractive errors, especially high hyperopia, still present increased complication rates and one should take into account the reduced safety profile prior to treating patients with a spherical equivalent higher than 3.0 D.

While Presby LASIK has demonstrated promising visual outcomes—restoring an extended depth of focus (EDOF) with a mean addition effect of +1 to +2 D—it still lacks robust long‑term evidence regarding its stability and safety. Available follow‑up suggests it is most effective in younger presbyopic patients (lower than 55 years) and may work particularly well in hyperopes. However, variability in laser platforms, ablation profiles, and patient selection hampers the formulation of clear indications and predictable outcomes. Finally, its impact on future cataract surgery can be challenging, since alterations in corneal sphericity must be accounted for when calculating IOL power.

What are the indications and contraindications for Keratorefractive Lenticule Extraction? (Question [include number from big document])

Limits of application KLEx:

• Myopia lower than 8.00D (GRADE +)
• Myopia higher than 8.00D only in case of a regular cornea, without any risk factors, and a sufficient corneal thickness, taking into account the cap and lenticule thickness and residual estimated thickness (GRADE +)
• Astigmatism lower than 5.0D, however laser platforms that do not provide cyclotorsion compensation, are able to correct only lower than 2.0D. (GRADE +)
• The CE-mark for hyperopic KLEx (only on Zeiss platform in Nov. 2025) has recently been approved with the application limits set at +6D for sphere and +4D for cylinder. However, there is still limited evidence regarding the long-term safety and efficacy of the procedure. (GRADE +)

The application limits must account for a minimum preoperative corneal thickness of 480 µm in the absence of additional risk factors (recommended is a thickness of 500 thickness), with an ideally preserved residual stromal bed of at least 300 µm. Under no circumstances should the residual stromal bed fall below 250 µm. It is crucial to emphasize that in any form of corneal subtractive surgery, the decisive parameter is not corneal thickness alone, but rather the total ablation volume relative to the corneal architecture. (GRADE +)

Efficacy

What is the efficacy of Keratorefractive Lenticule Extraction? (Question [include number from big document])

KLEx is effective for correcting moderate to high myopia (lower than 8.0D) and/or astigmatism (lower than 5.0D). The evidence for KLEx correcting higher degrees of myopia (higher than 8.0D) is limited. (GRADE +)

The efficacy of KLEx is comparable to other corneal laser refractive surgeries and phakic IOL implantation for patients with low to moderate myopia. For myopia greater than 8D, phakic IOL implantation is preferred. (GRADE +)

Predictability

What is the predictability of Keratorefractive Lenticule Extraction? (Question [include number from big document])

KLEx has an adequate predictability for correcting moderate to high myopia with or without astigmatism (lower than 2.0D). (GRADE +)

The predictability of KLEx is comparable with other refractive surgery procedures including LASIK and phakic IOL implantation when correcting moderate to moderate myopia with or without astigmatism. For myopia greater than -8D, phakic IOL implantation is preferred. (GRADE +)

No significant differences considering higher order aberrations could be found between KLEx and wavefront guided LASIK. KLEx might induce more vertical coma and trefoil, while wavefront guided LASIK might induce more spherical aberrations. (GRADE +)

KLEX showed a reduced risk in halo formation compared to phakic IOLS, while phakic IOLs showed better results in HOAs control. GRADE +)

It has to be noted that most of the current evidence has been based on the first available technology for KLEx (SMILE using VisuMax 500) with no cyclotorsion compensation.

Stability

What is the stability of Keratorefractive Lenticule Extraction? (Question [include number from big document])

The stability of KLEx for correcting myopia with or without astigmatism was found to be good. (GRADE +)

No difference in stability has been found when comparing LASIK and KLEX, after taking into account the learning curve. (GRADE +)

Safety

What is the safety of Keratorefractive Lenticule Extraction? (Question [include number from big document])

KLEx is safe for correcting moderate to high myopia with or without astigmatism. (GRADE +)

Compared to other procedures KLEx is as safe as other refractive surgery procedures including Surface Ablative procedures, LASIK, and pIOL implantation among patients with low up to moderate myopia with or without astigmatism. (GRADE +)

Efficacy, predictability, and safety of KLEx are comparable to LASIK, but KLEx still requires a learning curve and may become more widely used with the advent of new platforms, including those with cyclotorsion compensation. Advantages of KLEx include fewer dry eye symptoms than LASIK, and the absence of epithelial removal and flap creation. However, it is important to note that current publications on KLEx are based on the first generation of SMILE, which lacks cyclotorsion compensation. At this stage, KLEx does not extend its indications to corneal treatments in risky corneas. 

The KLEx procedure is purported to have fewer negative impacts on corneal innervation and ocular surface health, potentially resulting in a lower risk of short term postoperative dry eye compared to LASIK in the early postoperative period up to one year after surgery. However, beyond this timeframe, no significant differences between KLEx and LASIK have been observed. By cutting the lenticule in the deeper stromal layer while preserving the anterior stroma, which contains a denser nerve network and may act as a strength belt, KLEx minimizes disruption to corneal innervation. Despite this, postoperative dry eye, neuropathic corneal pain, and ectasia in risky corneas can still occur, albeit less frequently, even in patients without preoperative disease or specific risk factors. Surgeons should be aware of these potential complications and consider them during preoperative planning.

Theoretical advantages of KLEX over LASIK regarding corneal biomechanics still needs to be demonstrated. Although KLEx for myopia and myopic astigmatism appears to have the lowest incidence of postoperative corneal ectasia, reported cases in the literature, including those without preoperative forme fruste keratoconus or risk factors, suggest that post-SMILE ectasia may become a concern. Surgeons should remain mindful of these issues when considering KLEx.

Limited evidence exists regarding the efficacy of KLEx for correcting hyperopia and/or astigmatism. The first results indicate good efficacy in patients with hyperopia, but KLEx for hyperopia has just become available. As a result, predictability and safety data for hyperopic KLEx are also limited.

Retreatment management for KLEx remains to be codified. Generally, corneal surface ablations requiring MMC, procedures that convert KLEx into LASIK, as well as pIOLs, can be considered. Surface or conversion to intrastromal ablative techniques are typically used for low remaining refractive errors, while pIOLs should be considered for higher corrections, though very limited evidence is available in this regard. Regarding cross-linking applied under a flap or in the pocket during KLEx, its efficacy in reinforcing corneal biomechanics has not been demonstrated, like findings with PRK. Surgeons should carefully evaluate these factors when choosing refractive surgery options, ensuring informed decision-making and patient safety.

Customized treatment profiles are not currently available for KLEx, therefore significantly irregular corneas cannot be treated with topography- or wavefront-guided corrections as for LASIK and Surface ablations techniques.

What are the indications and contraindications for phakic IOL implantations? (Question [include number from big document])

PIOL is generally indicated for high ametropia, but principally is available for all refractive errors if the anterior chamber is deep enough. (GRADE +)

Limits of application pIOL implantations:

• Myopia higher than -1.0D, with an ACD depth ≥2.8 mm*.(GRADE +)
• Hyperopia higher than 1.0D, with an ACD depth of ≥3.0mm*(GRADE +)
• Astigmatism higher than 0.5 (GRADE +)

*ACD must be measured from the endothelium

In addition to the general selection criteria the following contraindications are specific for pIOL implantation:

Absolute contraindications

• ACD depth lower than 2.8mm in myopia and lower than 3.0mm in hyperopia. The ACD must be measured from the endothelium (ACD is defined as the distance from the apex of the posterior corneal surface to the apex of the anterior crystalline lens surface)
• Irido-corneal angle of lower than 30°.
• Recurrent or chonic uveitis, glaucoma or hypertony.
• The Instructions for Use (IFU) of each ICL/pIOL should be followed regarding the minimum endothelial cell density (ECD) count. Additionally, the endothelial cell density loss curve must be assessed to ensure long-term safety when considering anterior or posterior chamber pIOL implantation.((FDA), 2022)

Relative contraindications

• Presence of an iris or pupillary conformation and implantation anomaly
• Mesopic pupil size higher than 5.0mm

Efficacy

What is the efficacy of phakic IOL implantations? (Question [include number from big document])

The implantation of phakic IOLs is effective for correcting low to high myopia (higher than -1.0D) and/or astigmatism, showing a good quality of vision in terms of contrast sensitivity. (GRADE +)

There is only limited evidence about the implantation of phakic IOLs for correcting hyperopia with or without astigmatism to draw conclusions about the efficacy. (GRADE +)

Compared to laser refractive surgery, pIOLs are comparable effective in the short-term postoperative period to PRK, LASIK and KLEx in myopic eyes with or without astigmatism. (GRADE +)

Predictability

What is the predictability of phakic IOL implantations? (Question [include number from big document])

The predictability of implanting phakic IOLs for correcting up to high myopia (higher than -6.0D) with or without astigmatism is good. (GRADE +).

Evidence regarding the predictability of pIOLs implantation for correcting hyperopia and/or astigmatism is too limited. (GRADE +)

The predictability of pIOL implantation seems to be comparable to LASIK, PRK and KLEx in moderate myopic eyes (lower than -6.0D), however in high myopic patients (higher than -6.0D) the pIOLs seem to have a superior predictability. (GRADE +)

Stability

What is the stability of phakic IOL implantations? (Question [include number from big document])

Phakic IOLs for moderate to high myopia (higher than -6.0D) with or without astigmatism give stable results. (GRADE +)

There is poor evidence available about the stability of phakic IOLs for correcting hyperopia with or without astigmatism. (GRADE +)

Patients need to be aware that they will not keep a pIOL forever but will have to get a removal at the time of cataract and in case of any significant anatomical changes. (GRADE +)

Phakic IOL implantation remains a reversible procedure, however, it can result in permanent anatomical changes. (In retinal detachment surgery; AC pIOL will then be needed to be taken out.) Regular postoperative evaluations are crucial. (GRADE +)

Safety

What is the safety of phakic IOL implantations? (Question [include number from big document])

The implantation of phakic IOLs is safe for correcting moderate (lower than -6.0D) to high myopia (higher than -6.0D) with or without astigmatism. (GRADE +)

The implantation of phakic IOLs seems to be safe for correcting hyperopia with or without astigmatism, but the evidence is very limited as an ACD higher than 2.7mm is rare in high hyperopic eyes. (GRADE +)

The safety of phakic IOL implantation is comparable to laser refractive surgeries, including PRK, LASIK and KLEx for correcting myopia. However, for high myopia (higher than -6.0D), pIOLs are often preferred due to better potential for visual quality, even though refractive error predictability may be similar across procedures. Stability may be a concern with corneal-based procedures, as some regression can occur over time (GRADE +)

Surgical decisions must carefully consider the risk of cataract formation associated with but not exclusively PC pIOL implantation, as well as the potential for secondary ectasia following cornea-based procedures. Risk assessment depends on refractive status and eye morphology, always prioritizing patient benefit over risks. (GRADE +)

The increased risk of endothelial cell loss with all types of IOLs placed, but not exclusively, in the anterior chamber or iris fixated IOLs should be considered. (GRADE +)

The risk of pupillary block and sequential IOP increase is elevated in high hyperopia. In these cases, an iridotomy or iridectomy is mandatory. (GRADE +)

The safety of the procedure can be ensured by annual follow-up investigations including endothelial cell count, Anterior segment OCT focused on the angle, measurement of the IOP, assessment of vaulting and PCA, gonioscopy and assessment of the crystalline lens transparency. (GRADE +)

The presence of cataract after pIOL implantation requires removal of the pIOL followed by phacoemulsification or fs-laser assisted cataract surgery and IOL implantation. This procedure can be conducted in a one- or two-step procedure. The presence of a PIOL does not significantly impair biometry. (GRADE +)

Lens-based procedures involve addition of an AC or PC lens in a phakic eye. While PC phakic intraocular lenses (pIOLs) but not exclusively can lead to early cataract development requiring surgery, their predictability and efficacy are well-established for all types of ametropia.

For presbyopia, early approaches using posterior chamber pIOLs should be considered. Generally, pIOLs may offer a safer alternative to cornea-based procedures for patients with high ametropia or risky corneas. Long-term follow-up for patients with iris claw lenses, but not exclusively, is essential due to a significant decline in endothelial cell density, necessitating lifelong monitoring. Additionally, with two available profiles today (trifocal on the IPCL and EDOF on the ICL) results have yet to be reported.

Enhancement procedures such corneal laser correction for minor residual refractive errors or intraocular lens (pIOL) exchange may be necessary to optimize postoperative visual outcomes and improve patient satisfaction in cases of suboptimal refractive results.

Complications involving a rotated toric pIOL are often related to undersizing of the lens and may necessitate surgical intervention, such as repositioning or exchange of the implant, to restore intended refractive correction and visual stability.

Accurate sizing of posterior chamber pIOL is not yet perfect, although ICL and IPCL now have better nomograms, the predictability of lens positioning and vaulting remains a minor challenge. New AI-formulas can help to improve predictability.

Thresholds for follow-up of safety need refinement, as evaluating the safety of pIOLs requires a minimum of ten years, due to the slow, insidious response of the endothelium and the crystalline lens. In addition, any new model or even a new generation of a pIOL necessitates a fresh evaluation to ensure safety and efficacy.

More evidence is needed for pIOL implantation in hyperopic patients and presbyopic patients, particularly for presbyopia correcting pIOLs, where there is uncertainty about whether these lenses will accelerate cataract development.

Additionally, pIOL implantation encompasses more than just ICLs; data on other models, such as IPCL, is currently lacking. The long-term outcomes between PMMA and silicone foldable iris-fixated pIOLs also remain to be assessed.

What are the indications and contraindications for refractive lens exchange? (Question [include number from big document])

Refractive lens exchange can be considered in patients with various types of refractive errors, including hyperopia, myopia, astigmatism, and presbyopia. (GRADE +)

Refractive lens exchange may be considered for patients over 55 years old preferably after a posterior vitreous detachment (PVD), though PVD can be difficult to demonstrate clinically. It is also important that the peripheral retina shows no signs of lattice degeneration or other predisposing retinal lesions concerning the optical nerve or macula. Although no definitive age threshold exists, discussions regarding this procedure primary arise around the ages of 55 to 60, considering the residual accommodation provided by the crystalline lens during this period. However, in instances of high hyperopia (higher than 4.00D) with shallow anterior chamber depth and the absence of feasible alternatives such as corneal refractive surgery or pIOLs, earlier consideration may be warranted. (GRADE +)

Efficacy

What is the efficacy of refractive lens exchange? (Question [include number from big document])

Refractive lens exchange shows good efficacy in patients with high myopia (higher than -6.0D). (GRADE +)

Refractive lens exchange shows good efficacy in the correction of myopic and hyperopic astigmatism. (GRADE +))

Refractive lens exchange is effective for correcting low to moderate hyperopia (lower than 6.0D). (GRADE +)

Refractive lens exchange shows sufficient efficacy for correcting high hyperopia (higher than 6.0D). (GRADE +)

No evidence has been found for the efficacy of refractive lens exchange in low myopia (lower than -6.0D) (GRADE +)

Predictability

What is the predictability of refractive lens exchange? (Question [include number from big document])

RLE can be considered a predictable procedure in low (lower than 4.0D) to high (higher than 4.0D) hyperopes with a high number of patients receiving a postoperative SE within 1.0D of the target refraction. (GRADE +)

RLE can be considered a predictable procedure in low (lower than -2.0D) to high (higher than -6.0D) myopes. (GRADE +)

Stability

What is the stability of refractive lens exchange? (Question [include number from big document])

Refractive lens exchange shows good stability for correcting ametropia. (GRADE +)

Based on clinical expertise, refractive lens exchange is considered permanent, but eye changes over time can cause defocus due to lens positioning shifts (fibrosis) and retinal changes, especially in high myopia. Special attention is needed for patients developing against-the-rule astigmatism in the long term, often as a result to the corneal incision during the procedure. (GRADE +)

Safety

What is the safety of refractive lens exchange? (Question [include number from big document])

Refractive lens exchange can be considered a safe procedure for correcting low to high ametropia. (GRADE +)

High myopic patients undergoing RLE have an increased risk for a retinal detachment, especially in younger patients without cataract. (GRADE +)

Similar to cataract surgery postoperative inflammation, infection and DED need to be prevented. (GRADE +)

The surgery is exposed to mechanical damage of the bag that may increase the risk of complications and not allow the implantation of an in the bag IOL. (GRADE +)

RLE is the key procedure for addressing accommodation loss. Patient selection and information are particularly important, especially for those under 55, as a non-cataractous lens should be respected to minimize retinal risks and preserve residual accommodation.

Surgeons are still searching for the perfect concept, but last generation of Multifocal and EDF lenses achieve the goal in objective and qualitative vision. However, patients should understand that these lenses cannot restore accommodation but only compensate for its loss, which may always result in some decrease in quality of vision. Additionally, multifocal lenses require the achievement of emmetropia. EDF lenses may combine mini-monovision to enhance near vision, which can lead to an increase in halos at night. RLE can also be combined with other refractive procedures for enhancement.

A new category of patients, those with a history of corneal refractive surgery who are becoming presbyopic, must be considered. However, due to the lack of perfect predictability and potential impact on vision quality, RLE is not generally recommended for these patients. They should wait for the loss of crystalline lens transparency.

Special focus on ocular surface and tear film is crucial.

It is well described that removal of the crystalline lens results in a life-long increased risk for retinal detachment. This risk strongly increases in eyes with a long axial length. The risk for pseudophakic retinal detachment is considerably higher than one in a thousand eyes. Especially when the vitreous is still attached, the risk of retinal detachment is strongly increased.

Thresholds regarding age and axial length for intraocular lens (IOL) selection are yet to be precisely determined. Long-term stability, particularly considering lens bag aging, necessitates thorough examination, alongside the potential late onset of retinal complications and their impact on visual performance, possibly requiring IOL exchange. Special cases such as glaucoma and/ or AMD also demand thorough evaluation in the context of IOL choice.

Surgeons performing RLE or cataract surgery in patients with a history of corneal refractive surgery must carefully adjust their IOL power calculation formulas, for instance with the aid of specialized IOL power calculation websites. Additionally, it is crucial to assess the induced changes in the cornea to ensure the proper selection of IOL designs. The predictability and quality of vision in patients who have previously undergone corneal refractive surgery may be more affected than in patients with an unoperated, or ‘virgin,’ eye.

Most studies in the literature focus on cataract patients, with a relatively limited number of studies specifically addressing pure RLE patients. This highlights the ongoing challenge of distinguishing between true cataract cases and clear lens exchange in the 'grey zone.' A more thorough quantification of this distinction, including the use of advanced techniques such as Dynamic Light Scatter (DLI), Optical Scatter Index (OSI), and aberrometry or densitometry measurements (e.g., Pentacam), could provide greater insight into the differences and aid in defining appropriate surgical strategies.

Conflicts of interest can be found in the document linked below.

Declarations Of Interest (Refractive)