EyeWorld Asia-Pacific June 2013 Issue

59 EWAP DEVICES June 2013 present an intellectual challenge to the clinician and a therapeutic challenge to the patient.” Dr. Lemp added as many as 30% of people with clear, objective signs of dry eye are asymptomatic on subjective evaluations. Normal eyes don’t fluctuate on any of these scales, he said, whereas people with dry eye will be “all over the charts.” And it is precisely that variability that should alert clinicians to the presence of dry eye, he said. EyeWorld asked these specialists for their take on some of the newer diagnostic tests. Osmolarity Tear osmolarity is considered the best metric currently available, the experts said. Published literature confirms that assessment, 1 and the American Academy of Ophthalmology now specifically recommends tear osmolarity testing for the diagnosis and management of dry eye syndrome. 2 “Osmolarity is the most reliable metric we have,” Dr. Starr said. “It doesn’t distinguish between evaporative or aqueous deficient dry eye, however. Osmolarity as an objective measurement is the best single diagnostic that clinicians currently have to diagnose dry eye.” TearLab’s device has “demonstrated that any variable results are biological in origin. In other words, it’s not a crummy test, it’s a crummy disease with moment-to-moment variability in tear osmolarity. Any inter-eye differences of 8 mOsmol/L or greater are a clear indication of dry eye,” Dr. McDonald said. “I order a tear osmolarity test for anyone with a history of dry eye, anyone with complaints that sound like dry eye, anyone who is 40 or over, and anyone who is presenting preoperatively,” she said. Dr. Sheppard said in addition to the TearLab device, LacriSciences (Washington, DC) is developing the LacriPen, a handheld tear osmometer. Inflammatory markers Rapid Pathogen Screening (RPS, Sarasota, Fla., USA) has developed the InflammaDry, “the first and only rapid, point-of-care test to detect MMP-9, an inflammatory marker that is consistently elevated in the tears of patients with dry eye disease,” the company says on its website. “But it’s a nonspecific marker for inflammation,” Dr. McDonald said. So, for instance, a patient with a normal osmolarity test but a positive MMP-9 test has confirmed inflammation on the ocular surface—it’s just not dry eye, she said. Inflammation may be caused by surgery or by some other ocular disease, she said. “The InflammaDry test is nice because you take samples from the palpebral conjunctiva and within minutes you have a readout not unlike a pregnancy test—two lines and there’s excessive inflammation on the surface, one line there’s not,” Dr. Sheppard said. “This device has potential—in my practice it will be a synergistic or adjunctive test to run in addition to osmolarity and will help guide my treatment plan,” Dr. Starr said. Dr. Lemp believes the test has value, but perhaps more as a means to determine if a patient will respond to an anti-inflammatory. “It’s not very sensitive for mild- to-moderate disease, but is valuable for moderate-to-severe disease,” he said. Lipid layers The LipiView Ocular Surface Interferometer (TearScience, Morrisville, NC, USA) helps physicians assess a patient’s tear film; the second part of the system, the LipiFlow Thermal Pulsation System, treats the primary cause of evaporative dry eye—obstructed meibomian glands. “If the tear layer is too thin or the tear component is abnormal, then the associated treatment can be used to express the glands,” Dr. McDonald said. “It offers very valuable information; it’s a bit pricey but it is rapidly becoming a popular tool.” The system is invaluable for clinicians because it can precisely determine the health, thickness, and stability of the tear film and lipid layer, Dr. Starr said. “Targeting our treatments toward the underlying problem, whether it be aqueous deficiency or evaporative dry eye, obviously makes a lot of sense, and all of these tools help us accomplish that,” he said. OCT and microscopy Although the concept of using optical coherence topography (OCT) to evaluate the tear film is not a new one (Dr. McDonald presented on the idea in 2002), high-res OCT “actually shows a fair amount” of promise for imaging and measuring tear film thickness, she said. For one, OCT is not invasive, is exceedingly accurate, and can document tear film changes, Dr. McDonald said. “Because it doesn’t require contact with the ocular surface, it may be less affected by reflux tearing that the traditional tests have,” she said. The Keratograph (Oculus, Wetzlar, Germany) combines keratometric and corneal topography measurements, and “now comes with robust dry eye screening software,” Dr. McDonald said, including a noninvasive measurement of tear breakup time and tear meniscus height. She added confocal microscopy is also promising as a dry eye diagnostic. Final thoughts There is no “giant leap forward” in dry eye diagnostics that is going to occur, Dr. Sheppard said. “It will be a gradual improvement over time. There’s a war and there are thousands of battles every day in the clinics of America trying to stop progression and the condition that can lead to blinding corneal ulceration and significant deterioration and quality of life.” Just because these tests don’t all correlate with each other does not mean clinicians should only use one or the other, Dr. Lemp said. “These tests all measure a different aspect of the disease that comes into play at different stages of development for different people,” he said. Overall, taking the clinical guess work out of the equation in favor of objective testing is welcome, Dr. Starr said. “We shouldn’t shun any of these new diagnostics,” he said. “In fact, we should embrace them and incorporate them into our daily practice.” EWAP Editors’ note: Dr. Lemp has financial interests with Novagali (Evry, France), Merck (Whitehouse Station, NJ, USA), TearLab, TearScience, and a number of private equity firms. Dr. McDonald has financial interests with Oculus, RPS, and TearLab. Dr. Sheppard has financial interests with Alcon (Fort Worth, Texas, USA/ Hünenberg, Switzerland), Allergan (Irvine, Calif., USA), Bausch+Lomb (Rochester, NY, USA), LacriSciences, RPS, and TearLab. Dr. Starr has financial interests with Alcon, Allergan, Bausch + Lomb, Merck, RPS, and TearLab. References 1. Lemp MA, Bron AJ, Baudouin C, Benitez del Castillo JM, et al. Tear osmolarity in the diagnosis and management of dry eye disease. Am J Ophthalmol . 2011;111:792-798. 2. American Academy of Ophthalmology. Preferred practice pattern: Dry eye syndrome. 2011. Contact information Lemp : 202-255-6842, malemp@lempdc.com McDonald : 516-593-7709, margueritemcdonaldmd@aol.com Sheppard : 757-622-2200, docshep@hotmail.com Starr : 646-962-3370, cestarr@med.cornell.edu