In the journal Nature, Dr. Charles Czeisler discusses the function of intrinsically photosensitive retinal ganglion cells (ipRGCs) in regard to regulating circadian rhythm. Just as the ear has two functions (hearing and balance), so does the eyes. Light exposure at night, particularly in the wavelengths 459 nm to 484 nm,  has decoupled us from the 24-hour-day from which our bodies evolved. Longer wavelength blue light exposure at night is affecting melatonin secretion and limiting our sleep. The resulting sleep disorders have significant health effects, some of which can be life threatening.

Blue light affects the eye in three ways. First, the shortest wavelengths (about 400 nm to 430 nm) have the greatest effect on vision, as they are the most myopically defocused in front of the retina.

Second, short through medium wavelengths (about 400 nm to 460 nm) have the greatest effect in terms of photo-oxidative damage to the retina, contributing to the pathogenesis of Age-Related Macular Degeneration.

Third, longer wavelength blue light (about 460 nm to 490 nm) has the most effect on ipRGCs, telling the suprachiasmatic nucleus (our body’s internal clock) to suppress the secretion of melatonin from the pineal gland. We need long wavelength blue light exposure during waking hours to suppress melatonin to keep us alert. Seasonal affective disorder (SAD) has been linked to lack of exposure to long wavelength blue light. So while we need exposure to 460 nm to 490 nm light during the day, we don’t need it after sunset.

The optical lens industry has taken these findings and pushed ahead with the development of a coating to reduce the amount of the said blue light we are exposed to from our digital devices. To this end, Dr. Mei-Ling Chan Optometry has started recommending these coatings to our patients. Working with our lab HOYA, those patients whom we dispensed lenses coated with the Recharge EX3 coating are put into a weekly draw for a chance to win another set of lenses (from HOYA) FREE!  From now until December 24, come in and ask us about this fantastic coating!