Are sleep apnea and asthma linked to keratoconus?

An analysis of insurance data suggests keratoconus might be linked to sleep apnea and asthma, among other known connections.

The eye disorder causes the cornea to become thin and cone-shaped and can result in extreme decreased vision and increased sensitivity to glare and light. If keratoconus becomes too severe to correct and corneal perforation is at risk, corneal transplant becomes necessary.

The study, published in the journal Ophthalmology, compared 16,053 patients with keratoconus with patients without the eye disorder, finding higher risks among black and Latino patients when compared with white patients, and a lower risk among Asian patients. People who had sleep apnea, asthma and Down syndrome also had a higher risk.

Down syndrome, as well as family history, were already known links to keratoconus, says Sue Lowe, O.D., chair of the AOA Health Promotions Committee, who practices in Laramie, Wyoming.

While the findings are interesting, Dr. Lowe says there are several limitations. First, a retrospective longitudinal cohort study means researchers were studying data, not patients. Dr. Lowe also wonders whether the findings were skewed because the data were based on insurance coverage and did not include uninsured patients.

For both sleep apnea and asthma, Dr. Lowe points out that we don't know whether the various types of medication being prescribed for those conditions also might affect the cornea. "The cornea is one of the mostly highly metabolic parts of the body. If anything is interfering with the metabolism of our body, it can affect the cornea," she says. But even so, the study does not draw a causal link between sleep apnea, asthma and keratoconus.

A previous observational study also found a link between keratoconus patients and asthma and allergies, Dr. Lowe says. Those authors suggested inflammation may play a role, though the mechanism of progression is still unknown. That study was funded by the National Eye Institute and followed 1,209 keratoconus patients for eight years, starting in 1995-1996.

The AOA follows all research closely, including potential links to eye disorders such as keratoconus. Although this study has interesting findings, more research is needed regarding its influence on visual health.