Patients with severe obstructive sleep apnea-hypopnea syndrome (OSAHS) may have distinct differences in the endothelium compared with healthy subjects, a team of researchers from Greece suggests. Their study, published in Cornea, also found that a low level of REM sleep typically seen in these individuals may be a contributing factor to an increase in corneal thickness.

Specifically, the study found greater pleomorphism and polymegethism in the corneal endothelium of patients with severe OSAHS compared with normal eyes.

The prospective, comparative case series included 51 patients recently diagnosed with severe OSAHS and a paired, age and sex-matched control group of 44 healthy individuals. A total of 190 eyes were examined, including 102 eyes of patients with severe OSAHS and 88 eyes in the control group.

After a detailed eye exam, the researchers performed specular microscopy in all participants and compared corneal parameters between the groups. They also assessed the influence of the polysomnographic findings on corneal endothelial cell shape and central corneal thickness.

The researchers noted the central endothelial cell density and central corneal thickness were not significantly different between the groups. However, the variation of cell area was significantly higher and the hexagonal cell appearance was significantly lower in the OSAHS group. Additionally, the investigators observed a significant negative correlation between central corneal thickness and REM sleep.

“Our study highlighted the corneal endothelial alterations in patients with severe obstructive sleep apnea-hypopnea syndrome," says researcher Evangelia Chalkiadaki, MD. "This is the first time that increased pleomorphism and polymegathism of the central corneal endothelium was observed in apnea patients, probably as a result of chronic, intermittent hypoxia. We were also the first to observe that apnea patients with lower percentage of REM sleep had increased corneal thickness, which is an indicator of poor corneal oxygenation.”

The study suggests clinicians should be careful when dealing with the eyes of patients with severe OSAHS, especially when it comes to intraocular procedures such as cataract surgery, the researchers wrote in their paper.

Future controlled studies with larger sample sizes are needed to confirm the relationship between REM sleep and corneal thickness and to determine their clinical significance, the researchers suggest.