How Should I Approach the Fitting of My Post-Refractive
With numerous procedures often resulting in no need for contact lens correction, this refers to only the outcomes that were less than optimum. Obviously, corneal topography information, along with consultations with your laboratory consultant, are very important factors in the ultimate success of these patients.
In many cases, a reverse-geometry GP design is indicated if the topography map reveals an oblate corneal shape. Every laboratory typically has one or more such designs, which are typically larger than average (9.8-11.2mm).
Other options could include a hybrid design for post-surgical patients and, if the irregularity is moderate to severe, a scleral lens design.
Computer-assisted design programs can be very useful in designing lenses that mirror the oblate cornea and help prevent excessive central sagittal height and possible bubble formation.
The specific type of lens indicated often depends on the type of refractive surgery performed and the relative degree of corneal distortion. Generally, post-refractive surgery patients (LASIK, PRK) will fall into two basic categories:
- The oblate cornea, in which — as mentioned — a reverse-geometry design (limbal, scleral, or hybrid) will be the design of choice.
- The ectatic cornea, for which many keratoconus design options will work in addition to larger, intralimbal, hybrid, or scleral designs.
Post-RK patients will likely also have an oblate corneal shape that is less regular than the oblate shape of a post-LASIK or PRK patient. Post-RK patients may also have areas of ectasia that correspond to the RK scars. These patients may have significant fluctuations in vision and/or spectacle prescriptions as well. The severity of the visual impairment and fluctuations correspond to the number, depth, and proximity to the limbus of the RK incisions.
In these cases, a reverse-geometry GP or reverse-geometry scleral lens may help improve vision and decrease fluctuations (while the patient is wearing the lens). Following lens removal (especially scleral), patients may experience significantly different vision compared with pre-lens application, due to corneal changes that may occur during lens wear. Ensure no focal staining upon lens removal to confirm the proper lens fit.
As a rule of thumb, the more cuts present, the larger the lens needed. For RK patients with fewer incisions as well as post-LASIK ectasia, the hybrid lens has a good success rate. Using a flat-to-medium base curve hybrid lens usually obtains a comfortable fit with good vision.
The goal is to vault over the surgically altered central cornea and rest on the mid-peripheral region. If there is excessive central pooling or bubbles, then a reverse-geometry lens design is indicated.
GP Lens Institute/Scleral Lens Education Society
- Brujic M., Miller J. The Challenges of an Irregular Cornea.
- DeNaeyer G. Surgical Comanagement and Contact Lens Fitting.
- Benoit D. Multifocal GPs for Post-Surgical Eyes.
GP Lens Institute Advisory Committee members: Bruce Anderson OD, Marlane Brown OD, Carmen Castellano OD, Walter Choate OD, S. Barry Eiden OD, John Laurent OD, PhD, Derek Louie, OD, MS, Joe Shovlin OD, Frank Weinstock MD, Bruce Williams OD.