contact lens case reports

Design Flexibility Improves Success for Complex Cornea

BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO

A 36-year-old female underwent bilateral corneal transplants for keratoconus in Budapest, Hungary in the mid 1990s. She was referred to our specialty clinic at Pacific University because she could not tolerate her current GP lenses for more than two hours a day. The patient had failed with more traditional corneal lens designs and most recently had been fitted with scleral GP lenses.

These lenses were extremely uncomfortable due to excessive inferior edge lift that was worse in the right eye than in the left.

Corneal topography showed a significant corneal ectasia OD, with dioptric powers ranging from 42.50D to 56.50D (Figure 1). There was significant inferior thinning and steepening at the inferior graft-host interface resulting in a highly asymmetrical cornea (Figure 2). The left eye demonstrated a more normal anterior segment shape, but exhibited 7.50D of with-the-rule astigmatism (Figure 3). Both corneas exhibited significantly steeper than normal midperipheral corneal and scleral slopes.

Figure 1. Patient's axial corneal topographies.

Figure 2. Patient's right eye.

Figure 3. Patient's left eye.

Diagnostic Fitting

We diagnostically fit the patient with the SoClear lens (Art Optical Contact Lens), a 14.0mm GP lens manufactured in Boston XO (Dk = 100, Bausch & Lomb).

We selected the initial diagnostic lens base curves by calculating the mean dioptric power from the corneal topography maps. Fluorescein was instilled into the bowl of the lenses before application.

When fitting the SoClear lens, a light feather touch should be visible at the center of the cornea with moderate midperipheral clearance and an even distribution of peripheral (scleral) bearing. This fitting philosophy is somewhat different from other scleral lens designs, which strive for more definite apical clearance.

We were unable to achieve the "optimum" suggested fluorescein pattern for this patient, but we were close enough that when the scleral radii were steepened (to accommodate the excessive mid-peripheral and peripheral slope), the final lenses provided all-day lens comfort and 20/20 vision OD and OS.

This case demonstrates how the flexible design attributes of the SoClear lens can be independently adjusted to fit complex corneal and scleral shapes. CLS

The authors would like to thank Mike Johnson at Art Optical for his expertise and guidance in this case.

Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Paragon Vision Sciences. Mark André is an associate professor of optometry at Pacific University. He is also a consultant for CooperVision.