A soft contact lens prevents UVA-induced damage in the rabbit lens

CBR member Frank Giblin, director of the Eye Research Institute, studies the lens of the eye. In the September 2012 issue of the journal Experimental Eye Research, Giblin analyzes if A Class 1 UV-blocking (senofilcon A) Soft Contact Lens Prevents UVA-Induced Yellow Fluorescence and NADH Loss in the Rabbit Lens Nucleus Invivo (Volume 102, Pages 17-27). Parts of the introduction of the article are shown below, with references removed.

"The possibility that UV radiation in sunlight may be a cause of human nuclear cataract continues to be controversial. While certain epidemiological studies have failed to find a link between sunlight and nuclear cataract, others have detected a possible connection. An unusually high incidence (nearly 70%) of nuclear cataract has been documented for individuals in their sixth decade of life in regions with high UV exposure, including Singapore, Indonesia, India, and two subtropical regions of Japan. Truscott has hypothesized that it may only be past the age of 50 that the human lens nucleus becomes vulnerable to UV-induced protein damage. At this age in the human, a substantially decreased level of reduced glutathione in the lens nucleus can cause normally protective kynurenine UV filters to bind to lens proteins, possibly leading to toxic interactions between UV light and lens nuclear crystallins. Once nuclear cataract begins to form in the human lens, the opacity proceeds rapidly, possibly too fast for epidemiological studies to detect a correlation with cumulative sunlight exposure.…

It has long been known that as the human lens ages, there is a significant increase in the level of fluorescence, much of it the result of excitation by UVA wavelengths present in sunlight. The fluorescence appears to be concentrated in the lens nucleus where it may be involved in the development of nuclear cataract. Beginning at about the age of 60, increased fluorescence in the human lens can produce an elevated level of veiling glare, resulting in substantial loss of sharp vision. The present study investigates the effects of an acute in vivo dose of 365 nm light on subsequent UVA-excited fluorescence in the rabbit lens, and the ability of a Class I UV-blocking contact lens to prevent the fluorescence effects, as well as UVA-induced loss of lens pyridine nucleotides. Class I silicone hydrogel contact lenses contain UV-blocking materials that absorb more than 99% of incident UVB radiation and 90% of UVA... We have previously shown that these contact lenses are beneficial in protecting ocular tissues of the rabbit against harmful effects of UVB light, including photokeratitis and anterior subcapsular cataract."

This journal also published “highlights” or bullets summarizing the main results

► Rabbit eyes were irradiated with 365 nm light (100 mW/cm²) in vivo for 1 h ► Isolated lenses under 365 nm light showed yellow fluorescence from the nucleus. ► UVA-exposed lens λ-crystallin showed 6-fold higher yellow fluorescence than control. ► The UVA caused 53% loss of NADH in the lens nucleus and 13% in the cortex. ► A senofilcon A contact lens prevented UVA effects on lens fluorescence and NADH.

A coauthor on this paper was OU undergraduate Catherine Fick, who participated in the Summer Undergraduate Program in Eye Research (SUPER) during summer 2010. Fick presented her results at the 2011 Meeting of Minds, and won an award for her research at the 2011 Sigma Xi Student Research Conference.

Giblin’s laboratory is supported by a grant from the National Institutes of Health.