Contact Lenses After Radial Keratotomy
Centration is a challenge in fitting contact lenses after RK because the corneal apex is displaced to the midperiphery (Fig 11-2). Frequently used fitting techniques involve referring to the preoperative keratometry readings and basing the initial lens trial on the average keratometry values. Contact lens stability is achieved by adjusting the lens diameter. In general, larger-diameter lenses take advantage of the eyelid to achieve stability. However, they also increase the effective steepness of the lens due to increased sagittal depth. If the preoperative keratometry reading is not available, the ophthalmologist can use a paracentral or midperipheral curve, as measured with postoperative corneal topography, as a starting point.
When a successful fit cannot be obtained with a standard RGP lens, a reversegeometry lens can be used. The secondary curves can be designed to be as steep as necessary to achieve a stable fit. The larger the optical zone, the flatter the fit.
Figure 11-2 Fluorescein staining pattern in a contact lens patient who had undergone RK and LASIK shows pooling centrally and touch in the midperiphery. This pattern is the result of central corneal flattening and steepening in the midperiphery.
(Courtesy of Robert S. Feder, MD.)
Hydrophilic soft lenses can also be used after RK. Toric soft lenses can be helpful when regular astigmatism is present. Soft lenses are less helpful in eyes with irregular astigmatism because they are less able to mask an irregular surface. Lens designs such as hybrid contacts, which consist of an RGP center surrounded by a soft contact lens skirt, and scleral RGP lenses, which vault the cornea and contact the perilimbal conjunctiva/ sclera, may be helpful for patients with significant irregular astigmatism who are intolerant of conventional RGP lenses.
Whenever contact lenses are prescribed for post-RK eyes, as in the preceding scenarios, the ophthalmologist should continue to monitor the cornea to check for neovascularization of the wounds. Should neovascularization occur, contact lens wear should cease. Once the vessels have regressed, refitting can commence.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.