Sleep apnea patients at glaucoma risk

People with obstructive sleep apnea syndrome (OSAS) are prone to suffer from glaucoma at a rate about 10 times higher than non-OSAS sufferers, according to a study. While unraveling the details of glaucoma sufferers with normal eye pressure levels, the study found that optic nerve could be damaged due to hypoxia without a spike in eye pressure.

Glaucoma is thought to be a disease in which the optic nerve sustains damage due to increased eye pressure, resulting in a restricted visual field. "However, it has been technically difficult to continuously measure eye pressure in sleeping subjects. To address the problem, we employed a special sensor akin to a contact lens to monitor pressure changes when OSAS patients' breathing repeatedly stopped during sleep," said Yasuhiro Shinmei, researcher, Hokkaido University.

Normally, intrathoracic pressure is known to rise if people stop breathing (exhaling), resulting in higher eye pressure. However, 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. They also experienced hypoxic effects, as cessations in breathing cause blood oxygen saturation levels to drop, possibly triggering optic nerve damage that can lead to glaucom