A body of research has shown that many health problems associated with old  age, including memory loss, cancer, and heart disease, may be attributed to aging of the eye.
The gradual yellowing of the lens and narrowing of the pupil that naturally occur over time were previously thought to have only ocular effects. Now, researchers argue that by letting less and less sunlight pass through the lens to the retina, these aging processes inhibit the activation of important photoreceptors that regulate the body's circadian rhythms.
Circadian rhythms encompass the cyclical hormonal and physiological processes that mobilize the body during the day and slow it down for rest at night. These rhythms depend on light to function properly and correspond to the 24 hour day/night cycle. Studies have found that individuals whose circadian rhythms are out of sync, like shift workers, are more vulnerable to a variety of health problems. This is believed to be due to lower release of melatonin, a hormone with many health-promoting functions that plays an important role in circadian rhythm regulation.
As a result, cataract extractions that increase light entry to the retina may have benefits not only for the eye, but also for maintenance of circadian rhythms and overall body health. In addition, heightening one's exposure to natural sunlight and bright indoor lighting may limit the incidence of many age-related problems.*