CLINICAL EYE CAR
New technique could diagnose glaucoma sooner
January is Glaucoma Awareness Month. And as people make New Year's resolutions to improve their lifestyles, they should include adding a comprehensive, dilated eye examination to detect glaucoma, says Leo Semes, O.D.
What this describes is a next-generation imaging device that allows retinal ganglion cells to be visualized.
"If the public made a resolution to get their eyes examined before Valentine's Day...that would be a good message," says Dr. Semes, former professor at the University of Alabama - Birmingham School of Optometry.
It's a good time for doctors of optometry to have a conversation with patients at risk for the second-leading cause of blindness worldwide, Dr. Semes adds. This includes adults over age 60, African Americans and Hispanics over 40, and people with a family history of glaucoma, according to the National Eye Institute (NEI).
Sneaky symptoms, speedier diagnoses
Dr. Semes speaks from personal experience. His grandfather and mother both endured glaucoma. The eye condition influenced their quality of life. "Today we have better means of treatment, which may have resulted in a better outcome for them," Dr. Semes says.
The challenge with glaucoma is that its symptoms sneak up on patients. The earlier the diagnosis the better. A new imaging technique attempts to give eye doctors another option for catching the condition quicker. Published Jan. 2 in the Proceedings of the National Academy of Science of the United States of America, the study, "Imaging individual neurons in the retinal ganglion cell layer of the living eye," looks at retinal ganglion cells (RGCs) whose death are mostly liable for the loss of vision in glaucoma. Researchers in the study took a current technology—confocal adaptive optics scanning light ophthalmoscopy—and adapted it to capture views of separate RGCs within the retinas of a small number of monkeys and humans.
"The ability to image these cells in the living eye could accelerate our understanding of their role in normal vision and provide a diagnostic tool for evaluating new therapies for retinal disease," wrote researchers at the University of Rochester Medical Center.
Intraocular pressure is measured using applanation tonometry. The reading is altered by many factors, the most prominent of which is central corneal thickness, Dr. Semes says.
He also noted that the study's human subjects had normal retinas or early age-related macular degeneration. Individual RGCs have been viewed as hard to detect, described as "nearly perfectly transparent." More work is needed before it can be applied to clinical practice, he says.
Murray Fingeret, O.D., was encouraged by the results but added that more research was needed on the effectiveness of the new technique. Dr. Fingeret is chief of optometry at Department of Veterans Affairs, New York Harbor Healthcare System in Brooklyn, New York, and the first doctor of optometry appointed to the board of directors of The Glaucoma Foundation, where he continues his life's work of research and collaboration to find a cure.
"What this describes is a next-generation imaging device that allows retinal ganglion cells to be visualized," Dr. Fingeret says. "The cells are visualized due to an improvement in the optics of the device using adaptive optics.
"Currently, we image the retina and optic nerve to measure thickness of a tissue, such as the retinal nerve fiber layer, but we are not looking at individual cells," he says. "We are looking at a layer and then measuring its thickness. While this is important and an improvement from where we are now, this technology is still years away from being available commercially and it is not clear if this will be a clinical tool or one for researchers to understand the ways that glaucoma may develop and progress."
Dr. Semes was principal author of the AOA's clinical practice guide, Care of the Patient with Ocular Surface Disorders in 2010; a panel member for the clinical practice guide, Care of the Patient with Retinal Detachment and Related Peripheral Vitreoretinal Disease, and is one of the founding members of the Optometric Glaucoma Society and Optometric Retina Society.
He noted at least one study shortcoming: a possible contamination of the ganglion cell layer measurement in the presence of other neurodegenerative disorders. Otherwise, potentially, the new technique shows promise.
"Damage to the GCL (ganglion cell layer) has been used for several years as supportive (or pivotal evidence in equivocal cases) for a diagnosis and to assess progression in glaucoma," Dr. Semes says. "Recently, retrospective studies have suggested strongly that ganglion-cell loss may be the earliest structural change seen in glaucoma and that its progressive damage indicates an index in the absence of functional (visual field) changes.
"It is my opinion that the ganglion-cell population assessment is a powerful tool for initial insult as well as for assessing the trajectory of progression after baseline is established," he added. "In fact, studies have shown that this parameter may be more sensitive to progression than retinal nerve fiber layer thickness measurements."
With the national observance of glaucoma, the NEI's National Eye Health Education Program (NEHEP) recently reissued an updated "Keep Vision in Your Future: Glaucoma Toolkit."
Described as science-based and easy to understand, the kit aims to give health professionals tools to educate the public on the importance of comprehensive, dilated eye examinations in halting the progression of glaucoma in patients.
"It is meant for speakers to discuss glaucoma with an audience," says Dr. Fingeret.
"The slides run through who gets glaucoma, how glaucoma is diagnosed, and how it is treated. It is a simple presentation useful to present to patients. The kit comes with a speaker's guide as well as a fact sheet for audience members."
Dr. Semes noted a seeming contradiction in the toolkit's PowerPoint, specifically pages 14 and 19. And he noted that the presentation fails to mention visual field testing, part of a comprehensive evaluation for glaucoma. Still, both doctors applauded the presentation's intent: glaucoma awareness and its focus on the number 1 risk factor for glaucoma, elevated intraocular pressure.
JANUARY 9, 2017