Sleep apnea is a chronic condition that interrupts breathing during sleep. In obstructive sleep apnea, the airway becomes blocked, causing breathing to stop for up to2 minutes. This condition affects more than 12 million Americans. Its symptoms include loud snoring, gasping or choking while asleep, morning headache and daytime sleepiness.
Sleep apnea adversely affects the delicate and fragile vessels in the eye, particularly the retina, by sudden fluctuations of blood pressure and oxygen levels. During undisturbed sleep, the systemic blood pressure decreases slowly. Retinal vessels dilate to match blood flow based upon oxygen and metabolic demands.
In obstructive sleep apnea, oxygen levels drop rapidly and dramatically. Retinal vessels respond by dilating maximally to prevent retinal damage from oxygen deprivation or ischemia. The brain, however, responds to a lack of oxygen in the blood by releasing epinephrine and norepinephrine hormones that cause blood pressure spikes. These repeated hypertensive episodes throughout the night result in nests of micro-infarcts or mini-strokes and damage the retinal tissue.
Sleep apnea accelerates and compounds the abnormalities associated with diabetic damage to the retina. Diabetic patients can develop signs of impaired retinal blood flow and retinal micro-infarcts despite having a healthy blood sugar level. Decrease blood oxygen level in retinal capillaries and eye tissues triggers a release of chemicals that, in turn, could cause macular edema — excessive fluid in the macula — the center of the retina where perception of precise, sharp details of images occurs.
Ischemic optic neuropathy has also been associated with sleep apnea. This condition describes a mini-stroke of the optic nerve, the eye's direct connection to the brain. Optic nerve swelling from raised intracranial pressure is recognized in obstructive sleep apnea patients who often complain of headache upon waking.
More recently, sleep apnea has been identified as an independent risk factor for open-angle glaucoma — elevated pressure inside the eye to a level that damages the optic nerve causing a gradual loss of vision. Sleep apnea patients are nearly two times more likely to have open-angle glaucoma. Individuals who experience sleep apnea are encouraged to be screened for glaucoma.
Floppy eyelid syndrome is one of the most common ocular disorders associated with obstructive sleep apnea. Ninety percent of patients with floppy eyelid syndrome have obstructive sleep apnea. Apnea events prompt a sleeping position shift. The large, elastic upper eyelids become easily distorted and everted when they come into contact with pillow cases. These patients complain of chronic tearing, eye irritation and blurred vision; worse upon waking.
Additionally, apnea interferes with REM sleep — a stage of deep sleep when muscles are maximally relaxed and body systems are at maximum rest. Sleep apnea interrupts this overnight system reset, a condition that adversely affects an individual's physical and mental health.
Obstructive sleep apnea is more common in men than women. Typical apnea patients are middle-aged with a thick neck or narrow pharynx and have a body mass index of more than 28. Sleep apnea suspects also include children with enlarged tonsils, youngsters experiencing daytime sleepiness and adults whose partners report loud snoring.
Following sleep lab evaluations, successful treatments can be implemented to protect patients from the ocular and systemic ravages of obstructive sleep apnea.
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