Deep Sleep is Important for Corneal Health
METHODS AND RESULTS: The literature explains corneal nutrition being diurnally normal and nocturnally deficient as follows: closed eyelids lead to relative corneal hypoxia with a temperature rise that impairs the physiological thermal circulation and thus obstructs the aqueous supply of amino acids and glucose to the cornea. The cornea is left with residual circulation and nutritional deficiency when the eyelids are closed. Corneal metabolism becomes glycolytic under anaerobic conditions, and the glycogen stores are depleted. Moreover, closed eyelids cause the pH of the tear film to decrease with increasing CO2 partial pressure. This results in failure of the pH-dependent epithelial pumps that promote corneal drainage when the eyelids are open during the day. The cornea thus becomes thicker at night. Rapid eye movements during frequent REM sleep phases in the second half of the night ameliorate the nocturnal nutritional deficiency of the healthy cornea by shaking the aqueous humor, which stagnates during sleep.
CONCLUSION: The frequent recurrence of corneal erosion in the second half of the night may be due to a nocturnally intensified predisposing factor (nutritional deficiency of a previously damaged cornea) coinciding with a mechanical irritation (saccades during early morning REM sleep phases) in the case of a previously damaged corneal epithelium in conjunction with corneal dystrophy or microtraumas.
Hoffmann F, Curio G.
REM sleep and recurrent corneal erosion--a hypothesis
Klin Monbl Augenheilkd.
Augenklinik, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Germany.