Obstructive sleep apnea-hypopnea syndrome may have predisposition for evaporative dry eye

Penny A. Asbell, MD

It is an interesting study. Researchers looked at patients who were referred to a sleep clinic to be evaluated for sleep apnea. Patients were divided into those who were considered by the lab standards of their sleep findings to have obstructive sleep apnea and those who did not have obstructive sleep apnea.

Each patient had an eye examination, and per good clinical trial practice, the exams were performed by masked observers — they were not aware if the patient was or was not diagnosed with sleep apnea. Meibography to look at the meibomian glands was also performed, and meibomian gland dropout was then analyzed.

The study adds further evidence to what has been reported previously, that floppy eyelid is associated with obesity, which is associated with sleep apnea.

One has to be careful with any conclusions from this study. The correlation of two events does not mean that one event causes the other. It does not mean that sleep apnea causes abnormal lids or vice versa, but they are correlated, and they may both have the same underlying cause. One issue that comes to mind is both obesity and diabetes are associated with sleep apnea. Diabetes is associated with obesity, and then obesity may lead to floppy eyelid, which is often associated with obesity. A take-home “pearl” is correlation does not equal causation. The correlation presented is not surprising, but they have documented this further with their review; this is good.

One of the things to note about looking specifically at meibomian glands — evaluation is both interesting and difficult. There are not a lot of standard methods to evaluate meibomian glands and even fewer to determine what changes mean for clinical symptoms. It is difficult to standardize image analysis. Can analysis be done accurately and repeatedly? That is something the authors may want to explore further. In some studies, including ones I have been in, there has been an issue on the quality of the images. These researchers discussed a smaller study performed at only one site, so they may have had closer control of quality of the images that is often not available in large multicenter trials. In addition to image quality, how do you analyze the images? What is the method? Is it repeatable?

Lastly, we are still not entirely sure what changes in meibography really mean in terms of clinical function. It is something they should at least discuss or even explore further with their data. The jury is out for how best to interpret meibography images, how to collect data and how to interpret findings. Meibography is open for more research.

Overall, this is an interesting paper. It was well done, but remember that correlation does not equal causation. It is still not clear if meibomian gland dysfunction leads to obstructive sleep apnea. Nonetheless, at your next eye exam, ask about sleep apnea, evaluate lids for floppy lids and always do a review of systems, including noting diabetes and/or obesity. Take the time to get the history and evaluate the lids. We are just beginning to understand meibomian gland function and dysfunction.