Abstract
SIGNIFICANCE: Photochromic soft contact lenses contain light-sensitive additives that allow them to darken when exposed to ultraviolet or violet light. One question, however, is whether the lenses influence vision indoors (minimally activated). In this study, we found that the minimally activated lenses improved many aspects of visual function under bright light. PURPOSE: Photochromic contact lenses were designed to darken when exposed to outdoor sunlight. The filtering that results improves visual function under bright light conditions. Not all bright light exposures occur outdoors. In this study, we tested whether a photochromic contact lens improved visual function under conditions where the lens was minimally activated (i.e., no more than it normally would be in an indoor environment). METHODS: A subject-masked contralateral design was used comparing a photochromic contact lens randomized to one eye against a nonphotochromic contact in the other eye of the same subject. Sixty subjects (mean = 34.90 ± 11.24 years) were tested. The primary endpoints consisted of four visual function outcomes: photostress recovery, glare disability, glare discomfort, and chromatic contrast. Photostress recovery was quantified by measuring the time needed to recover visual acquisition of a grating target after 5 seconds of an intense xenon white flash exposure; glare disability was evaluated as the energy in a surrounding xenon white annulus necessary to veil a central grating target; and glare discomfort was assessed using bioimaging of the squint response. Chromatic contrast was measured as thresholds for a green-yellow (580 nm) grating target superposed on a blue (460 nm) background. RESULTS: The minimally activated photochromic contact demonstrated improved visual performance compared with the nonphotochromic control across all visual functions tested (P < .01). CONCLUSIONS: Even under conditions of exiguous activation (e.g., as would be expected indoors or while driving at night), a photochromic contact will improve many of the more deleterious aspects of bright light.