A novel ocular surface interferometer may help physicians more accurately diagnose and monitor lipid-deficient evaporative dry eye.
"The [interferometer] images the lipid layer of the tear film in very remarkable ways," said D. Rex Hamilton, MD. He discussed the interferometer during the annual meeting of the American Society of Cataract and Refractive Surgery.
"[The device] records high-resolution video using interferometry so that you can see through a false-color map the thickness of the lipid layer across the front surface of the cornea," said Dr. Hamilton, associate clinical professor of ophthalmology and director, UCLA Laser Refractive Center at the Jules Stein Eye Institute, University of California, Los Angeles. "The thickness of that layer has been correlated quite nicely with symptoms of dry eye. The thinner that layer is, the worse the patient's symptoms."
Techniques such as Schirmer testing and lissamine green staining are not sensitive or specific enough to stage the level of disease accurately, he added.
"We're hopeful, and we have some very encouraging data to suggest that this tool may be an objective way not only of quantifying the stage of disease but to demonstrate improvements following therapy," he continued.
Once the lipid layer gets thicker, the tear film tends to be more robust and the health of the epithelium improves, decreasing patients' symptoms and improving their comfort.
A study published in Cornea in 2009 demonstrated that three out of four patients reporting severe dry eye symptoms had lipid layer thickness less than 60 nm while three out of four patients without symptoms had lipid layer thickness greater than 75 nm.1
Having objective evidence of improvement would benefit both the clinician and the patient, suggested Dr. Hamilton. For the clinician, the interferometer results could confirm that the therapy being administered is effective, while patients, who are often frustrated by a series of unsuccessful treatment strategies, could gain confidence in a new therapy from seeing verification that their tear film is becoming healthier.
"We see it as a real advance, and I can't wait to get my hands on the clinical version of the device," said Dr. Hamilton, who was involved with the development of the interferometer and a companion treatment tool from TearScience, the LipiFlow thermal pulsation system, which is also under FDA review.