Eyeworld

Reporting from the XXXIII Congress of the ESCRS, September 5–9, Barcelona EW MEETING REPORTER 140 contain can induce and aggravate ocular surface disease, and a dam- aged ocular surface can negatively impact the efficacy of glaucoma therapy. How have glaucoma medica- tions made it to the market when their ingredients are toxic to the ocular surface? The problem with glaucoma drug development is that clinical trials don't represent real life, said Antoine Labbé, MD, Paris. During clinical trials, patients are treated for a period of months, when in real life, they are treated for years and even decades, Dr. Labbé said. In addition, clinical trials don't address the accumulation of drugs in the eye or the influences of other ocular surface disorders. Medication-induced ocular surface disease affects not only a patient's quality of life but also the efficacy of medical and surgical therapy—it has a direct impact on compliance as well as the outcome of filtration surgery. Compliance is a major issue in glaucoma thera- py, and in 2003, the World Health Organization stated that improving compliance has a greater impact on health than any improvement in medical treatment, Dr. Labbé said. In addition to compliance, the ocular surface has a critical role in the success of filtering surgery. Reviewing the available literature, Dr. Kotecha said. When the cornea is hard and stiff, GAT will overestimate the IOP, and when it is thin, soft, and flat, GAT will underestimate the IOP—as it often does after a patient has had refractive surgery. One alternative to GAT that could resolve this issue is dynamic contour tonometry (DCT). This con- tact tonometry method relies on a pressure sensor that contours to the shape of the cornea without deform- ing it. Because it does not deform the cornea, DCT is less likely to be influenced by corneal biomechanics, making it a more reliable method for measuring IOP in patients post refractive surgery. Whether DCT or another meth- od will eventually replace GAT re- mains to be seen, but the take-home message is that Goldman applana- tion alone is no longer sufficient for measuring IOP post refractive surgery, Dr. Kotecha said. To offer the best care, clinicians need to mea- sure IOP with several devices and integrate these measurements with imaging and visual field test results. It's complicated: Relationship between glaucoma and ocular surface disease A session at the EuCornea meeting explored the complex relationship between glaucoma and ocular sur- face disease. Both glaucoma medi- cations and the preservatives they predict, but Dr. Hommer suggested ways that clinicians can use rele- vant risk factors to better manage progressing patients and determine which patients have the highest risk of vision loss. Age, IOP, family history, and structure of the optic nerve head and retinal nerve fiber layer are a few of the risk factors to consider when assessing glaucoma progression. Consider a patient's life expectancy along with his or her age, Dr. Hommer said. If a patient is diagnosed with glaucoma at 65, he or she could live for another 20 years—plenty of time to go blind from glaucoma, he said. IOP fluctuates throughout the day in both glaucomatous and nor- mal eyes, and large IOP fluctuations have a huge effect on a patient's risk of progressing. IOP may seem to be well-controlled, Dr. Hommer said, but it often peaks outside of regular office hours and on average, that peak could be close to 5 mm Hg higher than what is measured in the clinic. Be aware that these fluctua- tions occur, he said, and be prepared to reevaluate target IOP when nec- essary—set a target IOP range rather than a specific value. Reexamining a 'gold standard' of measurement Lowering IOP is the mainstay of glaucoma treatment, and Goldmann applanation tonometry (GAT) is the gold standard for measuring IOP. Since GAT was introduced in 1957, its use in clinical practice has become nearly universal—but just how accurately does it measure IOP? During Glaucoma Day's first after- noon session, Aachal Kotecha, PhD, London, described the physical prin- ciple behind GAT, situations where it may be unreliable, and alternative methods for measuring IOP that could replace GAT as the industry standard. GAT measurements are based on the Imbert-Fick "law," which assumes that the cornea is infinitely thin, perfectly elastic, and perfect- ly flexible. These assumptions are incorrect, however, and studies have shown that corneal physical and biomechanical properties greatly influence the GAT measurements, October 2015 View videos from Saturday at ESCRS 2015: EWrePlay.org Marianne Price, PhD, discusses results of a study examining graft survival for DSAEK, DMEK, and PK. continued on page 142

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