Managing Corneal Graft Astigmatism and Irregularity
BY GREGORY W. DENAEYER, OD, FAAO
There are approximately 40,000 corneal transplants performed in the United States each year (National Eye Institute, 2013). The primary reason for patients to have corneal transplants is to restore vision after corneal disease or trauma. The three categories of corneal transplants include penetrating keratoplasty (PK) (full thickness), lamellar keratoplasty (partial thickness), and endothelial keratoplasty.
Many patients, especially those who have undergone penetrating keratoplasty, require contact lenses to maximize their visual success. GP lenses are often the best option for patients who develop postoperative high astigmatism or irregular astigmatism.
When to Fit GP lenses
It's paramount that you have good working relationships with patients' corneal specialists if you will be fitting patients postoperatively with GP lenses. Although there is no absolute rule on time, it is probably prudent to wait at least six months and have the surgeon's consent before fitting a patient after a corneal transplant. Grafts should be healthy, without complications, and topography stable. Remaining sutures that are intact and buried will not affect the fitting process or lens wear.
Choosing lens designs (e.g., corneal GPs or scleral lenses) depends on a number of factors. Prolate grafts with mild irregularity can often be successfully fit with corneal GP lenses. Switch to scleral lenses for moderate-to-severe irregularity to improve stability and comfort.
Scleral lenses will be more successful for a graft that has against-the-rule astigmatism because corneal GP lenses tend to slide horizontally in these situations.
Oblate-shaped corneal grafts may require a reverse geometry design to improve stability when fitting corneal GP lenses and to avoid midperipheral touch when fitting scleral lenses. Use corneal GP lenses made in hyper-Dk material to maximize oxygen transmission if grafts have diminished endothelial cell function.
Two follow-up appointments should be scheduled within the first six weeks after the final dispense to monitor patients for complications. If the result is successful, additional follow-up appointments will be dictated by patients' individual situations. Refits may be necessary if the corneal topography changes.
The prescribed lenses should provide patients with acceptable vision and comfort. Lens wear should not negatively impact the health of the anterior ocular surface. Educate patients to return if they experience foreign body sensation, as this may indicate loose or broken sutures. Instruct patients to report immediately if they experience pain, redness, or decreased vision. These symptoms may indicate lens-induced corneal complications, keratitis, or graft rejection. Check patients' intraocular pressure at emergency visits because graft patients are at greater risk for ocular hypertension (Oruçoglu, 2013). Monitor patients for the development of neovascularization, which can result from an ill-fitting corneal GP lens or a tight-fitting scleral lens.
GP lenses can be necessary for patients to achieve acceptable vision after corneal transplants in cases of high astigmatism or irregularity. Incorporating modern lens designs and materials into your practice will go a long way toward improving your success with these patients. CLS
For references, please visit www. clspectrum.com/references.asp and click on document #217.
Dr. DeNaeyer is the clinical director for Arena Eye Surgeons in Columbus, Ohio, and a consultant to Visionary Optics, B+L, and Aciont. You can contact him at firstname.lastname@example.org.