Changes after Everted Silicone Hydrogel Wear
Reports have recently emerged in the
ophthalmic literature related to topographical and refractive changes associated
with silicone hydrogel lens wear. In a Pacific University study, we found everted
(inside-out) lenses could induce significant corneal changes and that subjects consistently
rated everted lens comfort as equal to that of non-everted lenses.
To further test this, one of
us (PC), wore an everted –10.00D Night & Day lens (CIBA Vision) on
his amblyopic left eye for a continuous wearing period of 30 days. We took baseline
corneal topography measurements after the fitting and then follow-up measurements
after 10 hours, one week and four weeks of lens wear.
After 10 Hours Overnight
The difference display
little or no change at the center of the cornea. The area adjacent to the central
cornea showed approximately –1.50D of concentric flattening surrounded by
a zone of midperipheral steepening (Figure 1).
At one week, the central
apical power had flattened –1.37D. A distinct "central island" (zone of less
topographical change) was evident. Surrounding it was a concentric zone of greater
flattening (–4.50D at its flattest point). In the midperiphery, note a concentric
zone of corneal steepening
similar to that in GP corneal reshaping (Figure 2).
At four weeks, the central
apical power demonstrated –3.12D of corneal flattening. The central island
remained evident; however, the midperipheral cornea had flattened –6.75D at
its flattest point (Figure 3).
Despite the limitations
of this pilot study, we made two intriguing observations. First, wearing
everted silicone hydrogel lenses can result in significant topographical
changes. Second, patients can comfortably wear everted lenses for 30 days.
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: June 2005