Blue-blocking IOL can hinder scotopic vision, expert says

October 15, 2004

IOLs that block blue light, such as the AcrySof Natural IOL (Alcon Laboratories), trade scotopic visual performance for limited protection against acute UV-blue retinal phototoxicity, and they are a particularly poor choice for individuals whose scotopic vision is impaired because of conditions such as age-related macular degeneration (AMD) and diabetic retinopathy, according to Martin A. Mainster, PhD, MD, FRCOphth.

Editor's Note: In the following report, Martin A. Mainster, PhD, MD, FRCOphth, contends that IOLs that filter blue light provide minimal protection against acute UV-blue retinal toxicity and limit scotopic vision. In another article, Janet R. Sparrow, PhD, presents the results of a tissue culture study in which the blue light-absorbing design of one IOL was shown to protect retinal pigment epithelial cells from the damaging effects of light.

Dr. Mainster has been studying phototoxicity for several decades. During the second year of his ophthalmology residency in 1978, he published two papers warning that clear IOLs transmitted potentially harmful UV radiation between 330 and 400 nm to the retina.1,2 Within a decade, most IOLs were manufactured with UV-blocking chromophores. Dr. Mainster suggested in 1986 that it might be useful to block violet light in addition to UV radiation to reduce the risk of acute UV-blue phototoxicity.

"Ultraviolet accounts for 67% of acute UV-blue phototoxicity between 350 and 700 nm. Violet light is responsible for 18% of acute UV-blue phototoxicity, but it contributes only 5% of scotopic vision. That's why I suggested blocking violet light with IOL chromophores in 1986," Dr. Mainster said.3

"Conversely, blue light is responsible for 14% of UV-blue phototoxicity, but it provides more than 40% of scotopic vision. That's why I did not recommend blocking blue light. In addition to restricting UV radiation and violet light, the AcrySof Natural IOL limits blue and even some green light."