contact lens case reports
Correct Advanced PMD With Contact Lenses
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
Pellucid marginal degeneration (PMD) is a condition of unknown etiology that is hallmarked by a 1mm to 2mm-wide band of corneal thinning approximately 1mm above the inferior limbus. The thinning produces topographical maps with a characteristic "butterfly wing" appearance secondary to corneal steepening at 4 o'clock and 8 o'clock.
Figure 1. Patient WM's topographical
Optically Managing PMD
Spectacle correction is often successful in early stages of PMD because there may be minimal ir regular astigmatism. But as the condition progresses, the degree of against-the-rule astigmatism can exceed 5.00D. Contact lenses often provide these patients with the best level of corrected visual acuity.
Over the years we have successfully managed the condition with a wide range of contact lens designs including spherical and toric gas permeable lenses, piggyback lenses and toric soft lenses.
A Soft Toric Solution
Patient WM is a 38-year-old male with a 10-year history of PMD. Over the years he has been successfully corrected with spectacle lenses. Recent advances in his condition, especially in his left eye, have prompted him to consider contact lens correction.
At the initial presentation his manifest refraction was OD +0.50 4.00 x 85 20/25, OS +2.00 6.00 x 95 20/30. Keratometric readings were OD 43.12 @ 176/39.62 @ 86 with 4.50D of corneal astigmatism and OS 45.12 @ 4/38.25 @ 94 with 6.87D of corneal astigmatism. Topographical maps clearly demonstrated the typical butterfly wing appear ance that is almost diagnostic of PMD (Figure 1).
We elected to correct the patient's refractive error with toric soft contact lenses. We ordered a pair of CooperVision Frequency 55 toric lenses based on the patient's spectacle Rx vertexed to the plane of the cornea. We applied the lenses and allowed them to equilibrate (Figures 2 and 3). We then performed a careful spherocylinder over-refraction and entered the data into CooperVision's ToriTrack calculator.
|Figure 2. Photokeratoscopy OS before lens application.||Figure 3. Photokeratoscopy OS over the toric soft lens.|
We ordered the resulting contact lenses in the Frequency 55 toric design. Today our patient reports stable visual acuities of 20/20 and 20/25 and all-day lens wear.
Patrick Caroline is an associate professor of optometry at Pacific University and an assistant professor of ophthalmology at the Oregon Health Sciences University.
Mark André is director of contact lens services at the Oregon Health Sciences University and an adjunct assistant professor of optometry at Pacific University.