Everything you always wanted to know about…Posterior Capsular Rent: IOL Fixation

This is the third part of a series taking a detailed look at posterior capsule problems encountered during cataract surgery.

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This is the third part of a series taking a detailed look at posterior capsule problems encountered during cataract surgery. Dr Soosan Jacob MS, FRCS, DNB The type of IOL fixation to be employed after a posterior capsular rent (PCR) depends on residual capsular support as well as other ocular characteristics. Comorbidities such as iris structure and support, the presence of coexistent nucleus drop, and retinal or corneal pathology all need to be considered. In the case of fragment drop, it may be wiser to involve a vitreo-retinal colleague. IOL placement before referring to the retinal colleague depends on the size and density of the dropped nucleus/fragments. With small fragments or soft nucleus an IOL may be implanted. However, in case of large, dense fragments which may need to be brought up to the anterior chamber (AC), the eye may be left aphakic if the surgeon is insufficiently experienced with alternate IOL fixation techniques. All incisions should be sutured after a PCR to avoid wound leak and decrease the risk of endophthalmitis. The anterior or posterior segment surgeon may perform IOL fixation. Vitreous clearance using limbal, pars plana, or combined approach with 23/25-gauge instruments and vitrectomy systems in a closed globe technique via small incisions/sclerotomies and preservative-free triamcinolone to enhance visualisation are important. Hypotony during IOL fixation techniques should be avoided, preferably by using infusion by a trocar anterior chamber maintainer (ACM), simple ACM, or pars plana infusion cannula. Or, alternately, using viscoelastic. SULCUS PLACEMENT OF IOL A single-piece PMMA IOL or three-piece IOL with rounded edges may be placed in the sulcus. The preferred model is the three-piece foldable IOL because of the lack of a need to enlarge incisions. Avoid single-piece acrylic IOLs in the sulcus because of the risk of UGH (Uveitis-Glaucoma-Hyphaema) syndrome. The Staar AQ2010 IOL with firm 14mm long polyamide haptics and large 6.5mm optic generally allows stable sulcus placement, good centration, and vision. If there is possibility for posterior segment surgery required in the future, use acrylic three-piece IOLs as silicone IOLs interfere with vitrectomy procedures. Acrylic IOLs, however, have shorter haptics with a higher risk of decentration over time and are therefore ideally combined with optic capture. Avoiding IOL drop can be done by careful injection and direct visualisation of the leading haptic entering the sulcus. If needed, consider iris hooks to dilate the pupil. Unflexing the leading haptic tip within the cartridge, avoiding wound-assisted implantation, and holding a rod below the unfolding IOL optic also help prevent IOL drop. The trailing haptic is carefully dialled or flexed using a single-handed or bimanual handshake technique, ensuring release into the sulcus. An optic capture may then be performed. This allows central and stable IOL fixation, provided the rhexis is centred and smaller than the IOL optic, as described by Dr Howard Gimbel. After sulcus placement, the optic is gently captured by tilting each side downwards under the rhexis rim one after the other. In the absence of adequate capsular support for a sulcus IOL, choosing IOL fixation depends on the surgeon’s skill, experience, and individual preference. Whichever mode of fixation, the change in effective lens position results in necessary IOL power adjustment. AC-IOLs and iris fixated IOLs need proper iris support and tone, whereas scleral fixated IOLs are independent of the iris condition. ANTERIOR CHAMBER IOL When positioned carefully and properly sized, open-loop, angle-supported, four-point-fixated PMMA ACIOLs—such as Kelman Multiflex (Alcon)—are well tolerated. If not, however, they can cause long-term chronic endothelial damage and pseudophakic bullous keratopathy. Avoid ACIOLs in patients with inadequate AC depth, uveitis, glaucoma, or compromised corneal endothelium. IRIS FIXATED IOL Retro-iridial fixation is the preferred site and may be achieved either with a three-piece IOL using suture fixation or with an iris-claw lens. Poor iris tone may cause excess IOL mobility and consequent complications. Dr Garry Condon described how it’s possible to suture an IOL to the iris by placing the IOL behind the iris with an anterior pupillary capture of the optic. The iris is pulled inwards, and the pupil made round. Viscoelastic is used to contour the haptics, then sutured to the mid-peripheral iris using a modified Siepser sliding knot or a McCannel technique—using 9-0 or 10-0 polypropylene suture on a long, curved needle. The optic capture is then released. Retro-iridal fixation is also preferred over anterior fixation for the iris-claw lens to avoid the risk of long-term endothelial loss. Each haptic is introduced sequentially under the iris and enclavated. The optic should be released only after stable fixation. The site for iris enclavation should be chosen with care to avoid pupillary distortion. SUTURED SCLERAL FIXATED IOL There are reports of an association between both 9-0 and 10-0 Prolene sutures with the risk of long-term suture degradation. The 8-0 polytetrafluoroethylene (Gore-Tex) sutures may provide better long-term fixation. Numerous techniques have been described.Sutured scleral fixation can be performed ab-externo where a straight needle entering from one side under a scleral flap or via a scleral groove or Hoffman pocket is railroaded into a hollow bore needle passed in a similar fashion into the eye from the opposite side and externalised. A suture loop is brought out through a limbal incision, cut, and tied to each haptic of the IOL, then internalised. The suture is tied down to the sclera to fixate the IOL. In the ab-interno approach, sutures are tied to the IOL and passed from inside out. Various other techniques of suture IOL fixation have been described, such as Snyder’s cow hitch technique which gives four-point fixation, thus avoiding both tilt and torque. INTRA-SCLERAL HAPTIC FIXATION These have become popular techniques for IOL fixation in the absence of sufficient capsular support. They allow sutureless trans-scleral haptic fixation. Advantages include the absence of suture-related complications, independence from iris structure, ease of surgery, easy centration, long-term stability, and decreased pseudophakodonesis. It’s important to have sufficient vitrectomy prior to IOL implantation. And to prevent intra-operative hypotony, use an anterior chamber maintainer or pars plana infusion. Scharioth technique: Using 25-gauge end-gripping forceps, the IOL haptics are sequentially externalized through two ab-externo 24-gauge sclerotomies created 1.5 to 2mm behind the limbus. These are then fed into the 24-gauge, limbus parallel, half-thickness intra-scleral Scharioth tunnels that lead from the sclerotomies. Glued IOL: Introduced through 20- or 23-gauge sclerotomies (created under scleral flaps), 23- or 25-gauge end-gripping microforceps sequentially externalize both IOL haptics. Both haptics are then tucked into limbus parallel Scharioth tunnels, and the scleral flaps and conjunctiva sealed with glue. The intra-scleral haptic tuck within the Scharioth tunnel gives the glued IOL its stability, and therefore, a sufficient tuck is important. Double needle flanged intra-scleral haptic fixation (Yamane Technique): The haptics of a three-piece IOL are railroaded into the bore of 30-gauge thin-walled needles that are passed trans-conjunctivally and tunnelled through the sclera to enter intravitreally. Both needles are then externalized simultaneously, thus also externalizing the haptics. Low-temperature cautery is applied on the haptic tip to create a bulb-shaped flange that is then tucked back under the conjunctiva into the scleral tunnel. Dr Soosan Jacob is Director and Chief of Dr Agarwal’s Refractive and Cornea Foundation at Dr Agarwal’s Eye Hospital, Chennai, India, and can be reached at dr_soosanj@hotmail.com.