How Sleep Deprivation Harms the Eye to Adapt to Light

Eyes operate around the clock, adapting for changing levels of light with little effort on the conscious level. Stepping from the darkness of an interior room out into sunlight or turning off the glare of a bright computer screen at night, the eyes adapt automatically without conscious thought. But how does body harm arise from chronic sleep deprivation? Scientists have found that sleep loss ruins adaptation of the eye to light and renders it hyper-sensitive to light and slower to change.

The Physiology of Light Adaptation

Human vision is founded on light-processing photoreceptor cells, i.e., cones and rods. Cones, primarily responsible for color perception, work optimally in bright light, while rods help deal with dark environments. When the eye moves from darkness to brightness, pupils constrict to control entering light and photoreceptors adapt quickly not to feel uneasy.

However, this advanced system is interfered with by sleep deprivation. It is during deep sleep that the body works to repair and replace cells including the cells of the eyes. Through sleep deprivation, therefore, mechanisms for controlling the size of pupils, replenishing photoreceptors, and repairing neurotransmitters involved in vision decelerate. Hence, sensitivity to light intensifies and adaptation to changes in brightness deteriorates.

Strained Eyes and Increased Sensitivity

Ever had that searing sensation in the eyes following a sleepless night? That's not tiredness, that's proof of the eyes working hard to do their job without adequate rest. Sleep deprivation results in dry eyes, slowing tear production that acts as a cushion against irritation. Dryness accompanied by slow pupil responses makes bright lights brighter and darkness more confusing.