Impact of cataract surgery and intra-ocular lens replacement on endocrine and molecular ciracdian rythms, sleep and cognitive function in older adults

The role of light extends well beyond vision. After long-distance flights for example, going outdoors into daylight helps lessen the effect of jet lag. That’s because the light transmitted through the crystalline lens of the eye to certain cells in the retina impacts our inner biological clock, or circadian system. Exposure to daylight is needed for us to adjust our biological clock to actual, solar time, and therefore to synchronize and consolidate daily rhythms of many processes in our body. But what happens during the aging process, when the amount of light transmitted through the crystalline lens tends to decrease? Scientists know that the biological clock affects mood and behavior, but no one understands precisely how decreased light transmission affects the circadian system of the elderly. Nor is there much understanding of what happens when the crystalline lens is replaced by an artificial lens that blocks out certain types of light, for example during cataract surgery.
One of Europe’s foremost sleep scientists, Prof. Christian Cajochen, wants to find out to what extent an aging crystalline lens contributes to disturbances in the body’s circadian rhythm. The question is especially important because circadian rhythm disturbances have such a huge impact on the elderly – from hormonal rhythms, body core temperature and sleep to sleep-wake timing, cognition and mood.
Working with a team of European researchers, his project also focuses on the effects of lens replacement. Special attention is being paid to the effects of blue, relatively short light wavelengths, because replacement lenses often are designed to block blue light. The design is based on the theory that blue light might increase the risk for age-related macular degeneration. This matters because the photosensitive cells in the retina that affect the biological clock are especially sensitive to the blue, shorter wavelength part of the visible light spectrum.
Research results could lead to the development of new therapies to treat the biological clock disruptions that impact the quality of life for innumerable elderly persons. The results could also lead to recommendations for ophthalmologists who prescribe replacement lenses for their elderly patients.