A Valuable OSD Test

This essential test to identify inadequate lid seal has become so important in clinical practice that I find myself using it on close to 100% of my patients to help steer my ocular surface disease (OSD) management strategy. It helps to uncover one reason why so many patients have morning symptoms and inferior staining, or don’t respond to dry eye therapies.

When it comes to the eyelid, MGD, tear film, blink, and everything we focus on today in OSD, you’ve probably heard me reference Donald Korb, OD, a lead researcher and luminary in the field. This time, I’m sharing one of Dr. Korb’s most valuable tests, the Korb-Blackie (KB) light test, developed in conjunction with Caroline Blackie, OD. The test is essential to determining if a patient has inadequate lid seal, particularly in those with any inferior staining or morning symptoms. It’s also valuable in patients whose symptoms don’t resolve with treatment.

To conduct the KB test, have the patient lean back, look down and close (not squeeze) their eyelids as they would during periods of rest. In a darkened room, a transilluminator or penlight is placed along the closed upper eyelid at the end of the firm tarsal plate (without pushing forcefully enough to open it). Any light escaping from the lid margin will become evident inferiorly, indicating incomplete or inadequate lid seal.

Since the upper eyelid must slightly overlap the lower eyelid to create a proper seal, inadequate lid seal means the lids do not protect the ocular surface during sleep, often leading to desiccation and the inflammatory cascade. This condition should not be confused with lagophthalmos, the inability to close the eyelids, or more correctly, the inability to shut the lids so as to make apparent contact.

Treating incomplete lid seal properly (using ointments overnight,¹ short-term inflammation control, eyelid closure) is critical because misdiagnosing this as dry eye disease and treating these patients with long-term anti-inflammatory medications is analogous to treating painful corneal infections with anesthetics; it’s not getting at the root cause of the issue.

Dr. Korb’s incredible observations and research have changed how we manage OSD, bringing to light the underlying reasons why so many patients with inferior corneal staining don’t respond to traditional DED therapies.