Cataract Surgery Post-Keratoplasty

Knowledge of challenges and risks guides development of a clear plan. Cheryl Guttman Krader reports from the Virtual 12th EuCornea Congress. Performing cataract surgery in eyes with a corneal graft presents a variety of special considerations. Bruce Allan MD offered several practical insights to help guide surgical planning and technique in these cases. Preoperatively, knowing the risk of graft failure will not alter cataract surgery decision-making, but it is useful information for patient counselling and setting expectations about the possibility of needing further transplant surgery, Dr Allan said. “Failure becomes more likely when the endothelial cell count falls to below 800 cells/mm2, it becomes almost inevitable if the endothelial cell count is less than 500 cells/mm2, and it is certain to occur if the cornea is still oedematous at one month after cataract surgery,” he noted. For IOL decisions, Dr Allan said the general rule is to keep the choice simple. In particular, he advised against implanting either a multifocal IOL or toric IOL in a post-keratoplasty patient who is dependent on a rigid gas permeable contact lens to neutralise irregular astigmatism. In addition, he said he would be cautious about using a toric lens in eyes that are post-deep anterior lamellar keratoplasty or penetrating keratoplasty because the keratometry is often unstable in those cases. For management of irregular astigmatism, Dr Allan suggested the possibility of performing transepithelial PRK with wavefront or topography guidance before cataract surgery if the irregularity is moderate. If the irregularity is beyond the surface ablation’s treatable range, surgery will be needed to achieve gross shape correction before using the transepithelial PRK as a fine-tuning intervention. As a third step in what he termed a “1-2-3” approach, an implanted IOL can correct lower-order aberrations. INTRAOPERATIVE TIPS Most surgeons are probably routinely using a dispersive viscoelastic. But Dr Allan reinforced the value of this material for protecting the endothelium in post-transplant cases using an OCT image from a post-EK eye that showed colloidal gold-labelled viscoelastic adhering to the endothelium, even after extensive irrigation. Dr Allan added dispersive viscoelastic plays a dual role as an aid for enhancing visualisation. “It is a well-disseminated tip that dropping dispersive viscoelastic on the cornea instead of water really helps the view,” he said. Sealing the incision sites is another unique consideration in post-keratoplasty eyes—particularly if ectasia was the indication for the grafting procedure because late peripheral corneal thinning is likely in such cases. “Entry sites made through an area of thin cornea will not seal and must be avoided. It is very important to inspect the entire corneal periphery preoperatively and make a note in your surgical plan of where you will put the entry site.” While he observed that a scleral pocket incision is a useful alternative to a clear corneal incision in eyes with peripheral corneal thinning, Dr Allan noted that in the latter situation, surgeons might anticipate a need for incision suturing. “Don’t be afraid and don’t equivocate. The rule is that if you think about putting in a suture, you should probably do it,” he said. Bruce D Allan MD is a Consultant Ophthalmic Surgeon at Moorfields Eye Hospital, London, UK. bruce.allan@ucl.ac.uk