Influence of Blue Light Filtering Intraocular Lenses on Daytime Levels of Melatonin

The "blue light hazard" has been reported to cause retinal damage (oxidative stress), particularly to the central fovea due to its energetic, shorter wavelength visible photons, which is why blue-light filtering intraocular lenses have been developed for cataract surgery. The hormone melatonin has been reported to possess an efficient antioxidant capacity. Light information from the eye reaches the suprachiasmatic nuclei and inhibits melatonin secretion. Since melatonin is suppressed by light, we have a day-night rhythmicity, with increased levels at night. Melatonin suppression is wavelength-dependent with a peak sensitivity in the 446-477 nm (blue light) portion of the visible spectrum. The crystalline lens blocks most UV between 300 and 400 nm. The density of the lens increases with aging causing an alteration in the spectral absorption. The greatest increase in absorption occurs at the short wavelength end of the spectrum (around 400-470 nm). Age-related pupillary miosis and crystalline lens yellowing limit the blue light reaching the retina. This reduces the older adults' effective retinal light exposure to one tenth that of younger people. It has been shown that insomnia and depression decrease after cataract surgery and patients returned to youthful levels of melatonin. Since melatonin acts as an antioxidant, and more blue light filtering intra ocular lenses are implanted and thought to reduce photochemical damage in the macula, it would be interesting to show the positive influence of those blue light filtering intraocular lenses on daytime levels of melatonin in age-related macular degeneration patients.