Scientists at Hokkaido University have found out how ‘Obstructive Sleep Apnea Syndrome’ (OSAS) causes glaucoma. OSAS is a condition in which the person’s breathing stops during sleep for a significant period of time because of upper airway obstruction. Glaucoma is a condition in which optic nerve is damaged irreversibly leading to visual field defects and later serious vision loss. High intraocular pressure is a risk factor for development of glaucoma.
In the study, scientists measured the pressure of the eye during the sleep and were surprised to find that the pressure actually decreased during the episodes of apnea.
[Image by planetchopstick/ CC BY 2.0]
Normally, intrathoracic pressure is known to rise if people stop breathing (exhaling), resulting in higher eye pressure. The study found unexpectedly that the eye pressure dropped when subjects stopped breathing. The subjects tended to stop inhaling, not exhaling, due to airway closure, which should lead to lower intrathoracic pressure. The subjects also experienced hypoxic effects, as cessations in breathing cause blood oxygen saturation levels to drop, possibly triggering optic nerve damage that can lead to glaucoma.