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Inter-eye asymmetry may help identify glaucoma
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FT. LAUDERDALE, Fla. — A formula that compares the rim area and disc area of a patient’s two eyes may help differentiate people with glaucoma from those without disease, said one speaker here.
Alvine A. Kamdeu Fansi, MD, and colleagues analyzed four formulas for comparing inter-eye asymmetry of rim area and disc area (IEARADA) designed to differentiate normal and glaucomatous populations. Dr. Fansi spoke about their results here at the International Society for Imaging in the Eye.
“The rim-area-to-disc-area asymmetry may help to distinguish between normal and glaucoma patients,” Dr. Fansi said. “Several formulations of IEARADA exist. In this study, IEARADA 4, a ratio for the ratios, had the most correlations with Heidelberg Retina Tomograph (HRT) II.”
In the study, IEARADA values were calculated based on stereometric HRT values from formulas by Harasymowycz and colleagues (IEARADA-1), Hawker and colleagues (IEARADA-2), and two other formulas. IEARADA-3 was calculated by subtracting the value of smaller rim to disc area from the value of greater rim to disc area. IEARADA-4 is calculated by dividing the two previous values, Dr. Fansi explained.
The 472 participants in the study underwent confocal scanning laser ophthalmoscopy, frequency doubling perimetry technology and a complete exam. In all, 133 had normal results, 105 were glaucoma suspect and 234 had confirmed glaucoma, Dr. Fansi said. IEARADA -4 “seems to be the best asymmetry formula in order to distinguish between normal and glaucoma populations,” Dr. Fansi said. Only 50% of those with glaucoma had IEARADA -4 scores superior to 0.83 compared with 90% of those with normal results.
Study limitations included the reliability and accuracy of HRT II contour line, small sample size of normals and the selection was bias between suspect, normal and glaucoma patients, Dr. Fansi said.