Eyeworld

EW NEWS & OPINION 24 May 2016 by Liz Hillman EyeWorld Staff Writer Glaucoma specialists look forward to further research with the device that measures ocular volume changes A lthough IOP is considered the only treatable risk fac- tor for glaucoma patients, there is still much special- ists do not know about this measurement and how exactly it impacts disease progression. Part of that is due to the fact that IOP is usually measured during regular office hours, even though the majority of patients reach their peak IOP while laying down at night. Furthermore, measuring IOP during office hours doesn't ade- quately track fluctuations. While patients can be admitted to a sleep laboratory for 24-hour IOP moni- toring, this process is costly, time consuming, and cumbersome. Triggerfish (Sensimed, Lausanne, Switzerland) contact lens sensor (CLS), which recently received FDA approval for marketing in the U.S., could help obtain 24-hour metrics to assess IOP fluctuations, determine peak IOP, and ultimately provide better glaucoma management. The system, which received the CE mark in 2009, is described as a "first-of-its- kind product" that can be used to detect peak IOP variation patterns. Tony Realini, MD, professor of ophthalmology, and director of the glaucoma fellowship and clinical research programs, Centers for Neu- roscience, West Virginia University Eye Institute, Morgantown, West Virginia, said Triggerfish "sounds like a solution to the low sampling rate problem that prevents us from knowing our patients' true IOP fluctuations—why wouldn't we be excited?" Still, Dr. Realini thinks there is much physicians have to learn about the device—which can be applied in the clinic and then worn by patients as they go about their daily (and nightly) activities—before it can directly affect glaucoma assessments and treatment plans. Triggerfish measures the change in the corneal-scleral shape of the eye, not IOP in mm Hg directly. This measurement, however, has been shown to correlate with tonometry. 1 "Our group compared it to tonometry in the fellow eye of sub- jects housed within a sleep labora- tory and found that both methods detected peak IOP around the same time, approximately 4 a.m.," said Kaweh Mansouri, MD, adjoint associate professor, University of Colorado, Denver, and consultant ophthalmologist, Glaucoma Cen- ter, Montchoisi Clinic, Lausanne, Switzerland, who published these findings in 2015 in PLoS One. "In fact, the CLS measures a composite of IOP, volume, and elasticity of ocular tissues. The latter changes may reflect stress on the connec- tive tissues of the optic nerve head, the hypothesized site of glaucoma injury. Therefore, it is conceivable that CLS output may reflect changes [that] are more relevant to glaucoma damage than pure IOP." Other research involving the Triggerfish included a study present- ed at the 2015 American Glaucoma Society annual meeting, which eval- uated its use in 40 treated glaucoma patients. Researchers found it was "associated with the rate of visual field progression" and thus "may be useful in detecting eyes at higher risk of glaucoma progression while receiving treatment." 2 The single-use contact lens re- cords 300 data points for 30 seconds at 5-minute intervals, transmitting them wirelessly to an adhesive antenna worn on the patient's face around the eye. This information is then transmitted to a recorder worn around the patient's neck for later analysis by the physician. "This device provides a wealth of information that we have never had easy access to before," said Dr. Realini. "The temptation is to treat this information as IOP data—but it is not IOP. The data are, in essence, qualitative rather than quantitative. We can learn if and when IOP goes up, but not by how much in terms of millimeters of mercury. Since it does not provide IOP data in "First-of-its-kind" contact lens sensor for IOP monitoring receives FDA marketing approval Triggerfish consists of a contact lens with sensors that measure changes in the surface of the eye. This information is wirelessly sent to an antenna around the eye. Information is then stored by a recorder worn around the patient's neck. The single-use contact lens, designed for 24-hour monitoring, could help glaucoma specialists determine the best time of day to measure a patient's peak IOP and target treatment accordingly. Source: Sensimed

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