contact lens case reports

Fitting After Refractive Surgery: Is There Hope?

BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDR�, FCLSA
June 1999

Today's most common visual problems following refractive corneal surgery are related to under and overcorrections, which frequently result in anisometropia and a loss of binocular function. ss

Standard daily disposable or frequent replacement soft contact lenses often provide the necessary convenience and optical correction for many patients. However, more complex contact lens designs may be necessary for individuals with post-surgical irregular astigmatism, significant central corneal flattening or decentered ablations.

The Patient and The MacroLens

A 32-year-old male underwent bilateral PRK surgery in 1997 (OS in January and OD in March). His preoperative refractive error was OD -6.75 -0.75 x 180, OS -7.00 -0.75 x 175 with visual acuities of 20/20 OU. One year postoperatively, uncorrected visual acuities were 20/100 OD , 20/25 OS, and his residual refractive error was OD +4.00 -0.25 x 40 and OS -0.50 -0.50 x 165 (Fig. 1). Due to the patient's overcorrection OD and symptomatic anisometropia, we suggested contact lens wear. Numerous RGP and soft lens designs were tried and failed but were solved with the MacroLens (C&H Contact Lenses).

FIG. 1: Map of patient's OD post-PRK.

The MacroLens is a large diameter, semi-scleral RGP lens, available in diameters from 13.9mm to 15.0mm. Its advantages over traditional RGP designs include centration with stable optics over the pupil, total masking of all corneal cylinders and greater comfort due to scleral support. It has a large limbal fenestration vent to facilitate tear flow beneath the lens and to prevent lens adhesion. A diagnostic set of 12 lenses is available with base curves from 46.00D to 40.50D, and diameters from 13.9mm to 15.0mm.

Fitting Recommendations

Measure the visible horizontal iris diameter and identify the flat K reading. The optimum lens fit should exhibit relative alignment across the central and midperipheral cornea. A band of tear film pooling should be present at the peripheral cornea adjacent to the limbus (Fig. 2). This patient's post-surgical topography showed a slight pooling in the central cornea with excellent midperipheral lens alignment (Fig. 3).

FIG. 2: Optimum fluorescein pattern of the MacroLens on a normal, unoperated eye.

FIG. 3: The MacroLens on patient's right eye, post-PRK.

The MacroLens has been comfortable and versatile for many of our patients. Its ability to center on irregular and asymmetric corneas has made it an extremely important addition to our fitting armamentarium for the abnormal cornea.

Patrick Caroline is an associate professor of optometry at Pacific University and an assistant professor of ophthalmology at the Oregon Health Sciences University. Mark Andr� is director of contact lens services at the Oregon Health Sciences University.