Measuring tear film thickness

A customised broad spectrum OCT device can reliably measure tear film thickness without touching the ocular surface, according to  Gerhard Garhöfer MD, of the Medical University of Vienna, Austria. He expects commercial versions will be available soon that will give clinicians a user-independent measure of tear film break up time that will be helpful for diagnosing and monitoring dry eye disease. Dr Garhöfer conducted a study using ultra-high resolution OCT for assessing tear film thickness in 60 dry eye patients before and after administration of three commercial gel lubricants: hyaluronic acid 0.15% plus 3.0% trehalose (Thealoz Duo Gel); hyaluronic acid 0.2% (Hylo Gel); polyethylene glycol 0.4% plus propylene glycol 0.3% (Systane Gel). While 10 minutes after administration a pronounced increase in tear film thickness was observed in all three groups, hyaluronic acid with trehalose significantly maintained the increase in tear film for up to two hours, Dr Garhöfer reported. Beyond these immediate findings on dry eye gels, the study demonstrates that high resolution OCT can measure tear film without contacting the ocular surface, and provides operator-independent results. Drawbacks of the custom device include limitation to a 3.0mm segment of the ocular surface, and the high cost of light sources that can deliver approximately 1.0 micron resolution required for tear surface evaluation, Dr Garhöfer said. “We are working to make it larger so we can cover the whole surface so we can see exactly where the break up happens,” Dr Garhöfer said. He expects OCT machines with this capability will be commercially available soon. Gerhard Garhöfer: gerhard.garhoefer@meduniwien.ac.at