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Blue light-filtering IOLs may provide protection against potential blue light toxicity without significantly affecting clinical functioning of recipients, according to one ophthalmologist. Another cataract surgeon, however, contends that blue light filtering is not clinically important for preventing age-related macular degeneration and that further study is needed regarding the potential adverse effect of blue light-filtering implants on melanopsin production and scotopic vision.
"The question is no longer whether to use a blue light-filtering IOL, but which one to use," stated Dr. McCulley, professor and chairman of ophthalmology, University of Texas Southwestern Medical Center, Dallas.
"There are now a number of blue light-filtering IOLs on the market worldwide and more to be released, and we will see all sorts of variations and permutations as the market develops."
A variety of concerns arose when the blue light-filtering IOL technology first emerged, Dr. McCulley noted. Multiple studies, however, have demonstrated that these implants have no significant adverse effects on color or night vision, he said; nor do they interfere with glaucoma testing.
More recently, questions have emerged about the potential of blue-filtering IOLs to affect circadian functioning adversely by interfering with blue light activation of melanopsin. Dr. McCulley, however, said that blue light-filtering IOLs allow sufficient light transmission to retinal ganglion photoreceptors for melanopsin regulation.
"The blue light-filtering IOLs are associated with more melanopsin activation than the natural crystalline lens, which also decreases blue light transmission with aging, and they more closely mimic the normal condition that the human eye has evolved to over billions of years compared with a violet light-filtering IOL," Dr. McCulley said. "Violet-filtering IOLs allow more blue light exposure, but they filter 100% of the 420-nm violet light that also is needed for circadian photoentrainment."
The touted benefit of blue light-filtering IOLs for preventing AMD remains to be proven, he said. Although blue light is not a major risk factor in AMD, Dr. McCulley added, it is probably a factor.
"There are more than 540 articles in the peer-reviewed literature on blue light and the retina that strongly suggest it poses a toxicity concern," he said. "When the smoke clears on this question, there will be a fire. Will it be a big one? No, but there will be a small fire."
Most recently, Dr. McCulley mentioned, blue light filtration has been suggested to have other benefits, including inhibition of vascular endothelial growth factor production and prevention of increased proliferation of uveal melanoma.
"The latter association is also likely not a big issue, considering that we have not seen any epidemic of uveal melanoma after putting in clear IOLs," he said. "However, there does appear to be evidence that blue light filtration may have a positive effect." The documentation with regard to these potential beneficial effects appears stronger in the peer-reviewed literature than any negatives from such concerns as any circadian rhythm effects, Dr. McCulley added.