Sleep apnea’s interplay with corneal hysteresis

Excerpted from page 52 of the January/February 2018 edition of AOA Focus.

Sleep apnea's observed correlation with glaucoma development isn't yet understood, though new research seems to bolster thinking that doctors of optometry might want to pay close attention to those snores.

Published in the journal Optometry and Vision Science, the University of Malaya (Kuala Lumpur, Malaysia) research found an association between lower corneal hysteresis and moderate-to-severe obstructive sleep apnea syndrome (OSAS), potentially signifying another link between the common sleep disorder and glaucoma development.

This cross-sectional, observational study enrolled 117 subjects currently undergoing polysomnography for assessment of OSAS. These subjects were further divided into two groups, based on the Apnea Hypopnea Index, which is used to indicate the severity of OSAS. Group 1 comprised of those found within the normal-to-mild category, about 48%, while Group 2 comprised those in the moderate-to-severe category, about 52%.

Following a battery of tests that included measurements of central corneal thickness (CCT), corneal hysteresis, intraocular pressure (IOP) and Humphrey visual field (HVF) indices, researchers determined subjects in the moderate-to-severe group had lower corneal hysteresis than the normal-to-mild group. Furthermore, there were no statistically significant differences in IOP, CCT or HVF. Researchers note that a longer follow-up study would be needed to determine the "true nature" of OSAS morbidity.

"Further studies are indicated to determine the significance of this connection," the study concludes. "In the meantime, it may be prudent to monitor patients with more severe obstructive sleep apnea syndrome for the development of glaucoma."

Sleep apnea, glaucoma familiar territory?

However, this isn't the first study to indicate a correlation between sleep apnea and glaucoma. A 2016 study at Hokkaido University (Japan) found that people with OSAS were prone to suffer from glaucoma at a rate about 10 times higher than those without OSAS while a 2013 study from Taipei Medical University (Taiwan) found OSAS sufferers were 1.67 times more likely to be diagnosed with open-angle glaucoma following initial diagnosis of the sleep condition. But the connection between OSAS and ocular disorders doesn't end there.

The most common OSAS treatment option—the continuous positive airway pressure (CPAP) machine—can have negative effects on eye health, too. Such machines can leak or vent air from the sides of the mask, sometimes causing dry eye-type symptoms, but are vital for ensuring apneas don't become deadly. Therefore, protecting the ocular surface with thicker artificial tears, gels or ointments just before bedtime can help alleviate dryness.