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Study shows faster structural change in eyes with POAG
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FORT LAUDERDALE, Fla.— Eyes with primary open-angle glaucoma had a fivefold greater rate of structural change than eyes that did not have the condition, according to a scientific poster presented here.
Linda M. Zangwill, PhD, and colleagues reported their findings at the Association for Research in Vision and Ophthalmology meeting. They gave results of the Confocal Scanning Laser Ophthalmoscopy Ancillary Study to the Ocular Hypertension Treatment Study.
"These results suggest that measuring the rate of structural change can provide important information for the clinical management of ocular hypertensive patients," the authors said.
The study included 866 eyes of 439 patients who underwent Heidelberg Retina Tomograph measurement of topographic optic disc parameters. Data analysis also included age, race, IOP, horizontal cup-to-disc ratio, visual fields, corneal thickness and disc area.
The mean follow-up interval was 10 years; 64 eyes of 50 patients developed POAG.
Study data showed that the slope of rim area loss was markedly different from zero in eyes that developed or did not develop POAG. Rim area loss was appreciably faster in eyes that developed POAG than in eyes that did not.
"The rates of change of other topographic optic disc parameters including cap volume and rim disc ratio were also significantly faster in eyes that developed POAG compared to eyes that did not," the authors said.
Analysis showed that the slope of loss was markedly steeper in eyes with larger imaged cup-to-disc ratios at baseline, they said.
The natural history of structural changes in glaucoma are an acceleration of the normal steady decline that occurs as a result of aging. With regard to establishing the diagnosis of glaucoma, we generally utilize imaging technology to perform a “cross section” to see what the status is at that moment. If the structural measurements taken at that moment in time are within or outside the statistically average (or “normal”) range for the population, we declare the patient as not having or having disease, respectively. If you follow a patient over time and obtain multiple tests over the course of that time period, you may be able to generate rates of change of those measurements, even if each one of those studies falls within the average range. Those eyes that eventually went on to convert to glaucoma had a more rapid rate of change than those eyes that did not. This study gives us a potentially useful risk factor that is unique to imaging compared to clinical examination alone.
– Douglas J. Rhee, MD
OSN Glaucoma Board
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