The Sun Shows A Brighter Side

 The New York Times posted an article Aging of Eyes Is Blamed for Range of Health Woes, discussing a brighter side of the sun.  We see the many signs of aging, but one that may go unnoticed is the aging of the eye.  The gradual yellowing of the lens along with the pupil narrowing occurs with age and disturbs the body's circadian rhythm.  Circadian rhythms are "the cyclical hormonal and physiological processes that rally the body in the morning to tackle the day's demands and slow it down at night, allowing the body to rest and repair."  The internal clock relies on light in order to function properly.  Individuals such as shift workers possess circadian rhythms that are out of sync and therefore become greater at risk for a number of ailments, such as: insomnia, heart disease, and cancer.  

Looking back at the relation with age, as the eyes age, less and less sunlight is able to get through the lens and is not able to reach the keys cells in the retina that regulates the body's circadian rhythm, it's internal clock.  

Photoreceptive cells in the retina absorb sunlight and transmit messages to the brain, the suprachiasmatic nucleus.  This part of the brain controls the internal clock and adjusts the body to the environment by initiating the release of melatonin in the evening and cortisol in the morning.  Dr. Mainster and Dr. Turner estimated that by age 45 the photoreceptors receive 50% of the light needed to fully stimulate the circadian system.  When the age of 75 hits it dips down to a mere 17%.

These doctors believe that with age, people should make an effort to expose themselves to bright sunlight or bright indoor lighting.  Sun seems to be harmful to the skin, but for the eyes, the sun shows a brighter side.