Eye and Vision Care

Lifespan of sunglasses

02/28/2005 01:23AM

Question:

Do the ultraviolet-blocking chemicals in sunglass lenses lose effectiveness with time or cumulative UV exposure? Should non -prescription sunglasses be replaced after a certain number of years even if they appear to be in good condition? I`ve had my current pair (Bolles w/polycarbonate lenses) for nearly five years.

Answer:

Great question!

There are two different methods to provide sun protection for your eyes: one is with ultraviolet (uv) protection incorporated into the ophthalmic lens material. This occurs when you buy polycarbonate (a tough plastic) or photo-chromic (the ones that get darker when you are outside and lighten when you come inside) lenses. Another method is to apply a uv coating on the surface of standard glass or plastic ophthalmic lenses. Both methods should block 99% of the harmful uv radiation that could enter your eye (Note: you may get some direct or reflected light sneaking in from the side unless you have wrap-around glasses).

In the first method, no: uv protection lasts as long as the lens is worn. But in the second method, yes: uv coating can get scratched and eventually be rubbed off, and that severely affects its ability to protect your eyes.

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Response by:

Robert D. Newcomb, OD, MPH, FAAO
Professor of Clinical Optometry
College of Optometry
The Ohio State University