Obstructive sleep apnea is becoming an increasingly common disorder in the western world, with literature estimating somewhere between 14 to 49 percent prevalence in middle-aged men and around 10 percent in middle-aged women.
These are people already diagnosed, and I'm willing to bet there is a significant portion of people who have not been diagnosed.
In obstructive sleep apnea, the upper airway becomes obstructed, and the blood becomes relatively oxygen poor. The cycle then leads to a sympathetic nervous system response - think "fight or flight."
This leads to fragmentation of sleep, daytime fatigue, increased risk of cardiovascular disease, diabetes and cancer. A lesser-known correlation exists between obstructive sleep apnea and eye diseases like glaucoma.
The common misconception about glaucoma is that it's an eye disease of high pressure. Eye pressure is just one of many factors of the disease. Glaucoma itself is defined by optic nerve damage over time, which corresponds to gradual loss of peripheral vision.
While this often is caused or exacerbated by high intraocular pressure, there is normal tension, or low-pressure, glaucoma. These patients experience optic nerve damage without ever having eye pressures above "normal" ranges.
There is a lot to be investigated regarding Normal Tension Glaucoma, but one of the prevailing thoughts is that the optic nerve is not getting an adequate blood-oxygen supply.
We sometimes see this in patients who take their blood pressure medication at night. When the blood pressure dips low overnight, there is not enough supply to the optic nerve, and nerve damage occurs.
Sleep apnea could be mimicking this. Optic nerve damage would occur when the blood has low oxygen saturation and the nerve does not get adequate perfusion.
Glaucoma is not the only eye disease found to have a correlation with obstructive sleep apnea. Other eye diseases found to have higher prevalence in patients with sleep apnea are ocular surface disease, floppy eyelid syndrome (where the eyelid everts overnight and causes conjunctivitis from mechanical friction with the pillow), non-arteritic ischemic optic neuropathy (often called a stroke to the optic nerve) and papilledema (swelling to the optic nerve caused by raised intracranial pressure).
I don't think many people realize that sleep apnea is another reason for getting annual eye health exams. I am starting to ask more of my glaucoma and dry-eye patients about sleep apnea and CPAP use.
The human body is truly incredible and intricate in every way. We are fearfully and wonderfully made!
Caroline Bundrick, O.D. is an optometrist practicing at Darling Eye Center, with offices in Bluffton and on Hilton Head Island.