contact lens case reports
Finding the Cause of Soft Toric Lens Intolerance
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRé, FAAO

Figure 1. Right eye inferior microcystic corneal edema.
Figure 2. Left eye inferior microcystic corneal edema.

The patient is a 47-year-old female with a 15-year history of wearing soft lenses. We first evaluated her 12 months ago when her chief complaint was a growing intolerance to her 38 percent water polymacon, prism ballasted toric soft lenses that she replaced yearly. She used a multipurpose solution nightly for cleaning and disinfection.

Corneal Distortion

At the initial visit her visual acuities with contact lenses were OD 20/50, OS 20/30. A sphero-cylinder over-refraction revealed a minimal improvement in visual acuity. Manifest refraction OD was –3.75 –3.25 x 015, 20/40, OS –3.25 –5.50 x 175, 20/30. Keratometric readings were OD 44.00 @ 008/48.37 @ 098, OS 43.87 @ 170/50.37 @ 080.

Slit lamp examination showed bilateral micropannus, superficial punctate keratitis and inferior epithelial microcystic edema consistent with a localized corneal hypoxia (Figures 1 and 2). We performed photokeratoscopy and videokeratography. Both eyes showed significant inferior corneal distortion (Figure 3). We diagnosed her with possible hypoxia-induced corneal distortion and advised her to discontinue lens wear for four weeks.

When she returned one month later, manifest refraction was OD –3.00 –2.75 x 010, 20/20, OS –3.25 –3.00 x 170, 20/20 and keratometric readings were OD 43.50 @ 012/46.87 @ 102 and OS 44.00 @165/47.50 @ 075. Slit lamp examination showed no distortion by either photokeratoscopy or videokeratoscopy.

We refit her with Frequency 55 Toric XR lenses (CooperVision) manufactured in 55 percent water methafilcon A material, OD 8.4 –3.25 –2.25 x 010 14.4mm, OS 8.4 –3.25 –2.25 x 170 14.4mm. She's worn them for 10 months with no recurrence of corneal edema. Her visual acuities are 20/20 OU with no spectacle blur when alternating from lenses to glasses.

A Thinner Profile

This case demonstrates the long-term effects of wearing thick, low-Dk, prism ballasted soft lenses. While this type of edema response is rare, it illustrates that corneal hypoxia can occur in patients wearing traditional toric soft lenses. These patients may benefit from lenses that incorporate a thinner overall design profile and/or higher Dk materials.

Patrick Caroline is an associate professor of optometry at Pacific University and is an assistant professor of ophthalmology at the Oregon Health Sciences University. He is also a consultant to Paragon Vision Sciences and SynergEyes, Inc. Mark André is director of contact lens services at the Oregon Health Sciences University and serves as an assistant professor of optometry at Pacific University. He is also a consultant for Alcon Labs, CooperVision and SynergEyes, Inc.

Contact Lens Spectrum, Issue: September 2005