Preserving Aging Eyes (1 Letter) Re "Aging of Eyes Is Blamed for Range of Health Woes" (In Theory, Feb. 21): The spectrum of morning light necessary to trigger a positive circadian response is most effective in the long blue-green range. Scientists who study the aging human eye have found that the spectrum that increases the risk for macular degeneration is in the violet-blue range. Therefore, after a cataract operation, if the damaged lens is replaced with an intraocular filter that removes only violet-blue light and UV radiation, but allows blue-green light to reach the retina, the risk of macular degeneration will be decreased while still allowing for the necessary light to trigger a proper circadian response. Joan E. Roberts Manhattan The writer, a chemistry professor at Fordham University, conducts research in the area of circadian rhythm and prevention of macular degeneration.