Fuchs' and cataract

Cataract surgery can be complex and delicate, but especially so in eyes with Fuchs’ dystrophy, said Terry Kim MD, professor of ophthalmology, Duke University School of Medicine, Durham, North Carolina, US. He shared pearls for assessing patients, protecting the corneal endothelium, selecting lenses and determining when cataract extraction should be combined with endothelial keratoplasty at the American Academy of Ophthalmology annual meeting in New Orleans. Fuchs’-cataract cases generally fall into four clinical scenarios, Dr Kim said. The cataract is significantly worse; the Fuchs’ is significantly worse; the cataract and Fuchs’ are similar; or both diseases are advanced with anterior stromal haze present. Along with factors such as patient age and anterior chamber depth, these scenarios help determine whether to perform endothelial keratoplasty (EK) or cataract surgery alone, or to combine them. A case of severe Fuchs’ dystrophy with confluent guttae on retroillumination A slit-lamp exam is essential in making the decision to perform cataract surgery alone or combined with endothelial keratoplasty. Specular refection is a useful but often overlooked tool. Grading the severity of Fuchs’ dystrophy (FECD Multi- Center Study Group. Cornea 2012;31:26- 35) according to guttae number, location and extent of coverage, and the presence of clinically apparent stromal or epithelial oedema is useful. Specular microscopy may be indicated but is generally not necessary in most cases. Lens density and anterior chamber depth are also important. Also consider other ocular co-morbidities, such as an abnormal iris/pupil, pseudoexfoliation and weak zonules, that can make a combination procedure more challenging. Published guidelines for central corneal pachymetry vary, with some calling for 600 microns as a threshold (Duane’s Clinical Ophthalmology, 2003, Chapter 16A), and more recent data suggesting up to 640 microns (Seitzman et al. Ophthalmology. 2005 Mar: 112;441-6), Dr Kim noted. “But based on the variation of corneal thicknesses I’ve encountered in evaluating refractive surgery patients, I’ve found you can have quite a variation in pachymetry with a normal cornea, so you have to take this into account.” CLINICAL DECISION According to Dr Kim, the decision to proceed with a cataract surgery alone vs. a combined procedure with Descemet stripping endothelial keratoplasty (DSEK), Descemet stripping automated endothelial keratoplasty (DSAEK), or Descemet membrane endothelial keratoplasty (DMEK) is mainly a clinical decision based on the aforementioned factors. “I generally proceed with just cataract surgery if there is no morning blurring of vision, which means an absence of microcystic oedema, mild signs of Fuchs’ dystrophy and a lens density that I feel comfortable handling.” He recommends being comfortable with the ability to handle the density of the lens and depth of the anterior chamber in the setting of a potentially cloudier cornea and a smaller anterior capsulorhexis (which is generally performed in combined procedures to help prevent the intraocular lens from prolapsing forward during graft insertion and manipulation). Hard nuclei and/or shallow chambers may expose the corneal endothelium to greater risk of damage. Dr Kim also considers other factors including patient vision, age and aftercare compliance with medications, postoperative instructions, etc. Strong indications for combining EK with phaco include blurred morning vision, any sign of epithelial oedema, or significant guttae in terms of density or area of involvement. Documented increasing corneal thicknesses on pachymetry or asymmetric pachymetry also suggest endothelial dysfunction. Patients with occupational or other needs for clear vision may also require keratoplasty at the time of the cataract surgery. When performing phaco alone in patients with Fuchs’ dystrophy, Dr Kim suggested several surgical steps that could help relieve stress on the corneal endothelium during cataract surgery, often leading to better outcomes. “I highly recommend the use of dispersive viscoelastics in these cases,” Dr Kim said. These include Viscoat, Healon D and Ocucoat. Whereas cohesive viscoelastics wash out quickly once irrigation and aspiration begin, dispersive agents are much more retentive and stay in the anterior chamber, providing superior corneal endothelial protection.” Dr Kim also recommends performing phaco and irrigation/aspiration at or below the iris plane. This helps keep ultrasound energy, fluid turbulence and fragments away from the endothelium. Phaco power modulation, available on systems including the Bausch + Lomb Stellaris with Hyperburst, Alcon Infiniti/ Centurion with Torsional IP, and AMO Signature with Ellips FX, also reduce total ultrasound energy and improve outcomes, Dr Kim noted. His own research has shown that utilising torsional IP can increase ultrasound power efficiency, reduce fragment repulsion, decrease turbulence, enhance followability and reduce the risk of thermal wound burns. The result is lower ultrasound energy use, less endothelial trauma and less endothelial cell loss at six months (Berhahl et al. JCRS. 2008;34(12):2091-2095). PHACO TECHNIQUES Employing various phaco techniques such as horizontal and vertical chop manoeuvres can help minimise endothelial stress by substituting mechanical energy for ultrasound energy whenever possible. “As much as I can, I try to disassemble the lens into smaller fragments with the chopper as opposed to using ultrasound energy to emulsify these larger pieces. This further reduces stress on the endothelium,” Dr Kim said. For very dense brunescent cataracts, the Ultrachopper phaco tip, developed by Dr Luis Escaf for the Infiniti system, has been extremely useful for approaching those cataracts that have a resilient, leathery posterior plate that can be difficult to fracture with conventional techniques, Dr Kim said. The short, curved tip allows for the creation of a deep, narrow channel with phaco that can then be extended through a leathery posterior plate with a pre-chopper, reducing both ultrasound energy and the risk of a posterior capsule rupture. “I find many of these cases have a clear cornea on post-op day one.” Dr Kim recommends hydrophobic monofocal lenses for Fuchs’ patients. Hydrophilic lenses exposed to air injections in the anterior chamber during EK can opacify due to hydroxyapatite deposition (Werner et al. JCRS 2010; Patryn et al. Cornea 2012). Multifocal lenses can also be problematic because even mild corneal guttae can compound the reduction in contrast sensitivity. The refractive impact of EK also must be considered, Dr Kim said. DSEK and DSAEK induce about a 1.0 to 1.25 D hyperopic shift, which should be offset in combined cataract cases by aiming -1.0 to -1.25 D with the intraocular lens (Jun et al. Cornea 2009). DMEK causes much less hyperopia, with a correspondingly lower myopic offset. Hopefully, these pearls can help the clinician approach the patient with Fuchs’ dystrophy and cataract with a more systematic approach for surgical planning that will hopefully lead to better patient outcomes.