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Glaucomatous optic neuropathy is characterized by the progressive loss of retinal nerve fibers and neuroretinal rim. However, such loss occurs in healthy eyes as well.
Hammel et al. characterize the rate and pattern of age-related and glaucomatous neuroretinal rim area changes in subjects of African and European descent who were followed-up for 5.0 years (interquartile range, 2.0-7.4 years) using confocal scanning laser ophthalmoscopy. They found that the mean rate of global rim area loss was 3.7 times faster (-10.2×10-3 vs. -2.8×10-3mm2/year), and the mean rate of global percentage rim area loss was 5.4 times faster in progressing glaucoma eyes compared to healthy eyes (-1.1% vs. -0.2%/year), but considerable overlap existed between the two groups; 66% of progressing glaucoma eyes had a rate of rim area change faster than the fastest 5% of healthy eyes, and 38% had a rate of change faster than the fastest 1% of healthy eyes. Rates of change in healthy eyes of patients of African and European descent were very similar (-2.1×10-3 and -2.3×10-3 mm2/year, and -0.2% and -0.2%/year).
Since progressive rim loss is a universal finding with aging, it is important to differentiate glaucomatous rim loss from natural rim loss associated with aging
The rate of rim area loss reported in this study is largely similar with that found in the Ocular Hypertension Treatment Study. In the Ocular Hypertension Treatment Study,1 mean rates of rim area loss in eyes in which POAG developed and in in which it did not were -13.1×10−3 and -2.6×10−3 mm2/year, respectively (or -0.89% and -0.17%/year, respectively).
Since progressive rim loss is a universal finding with aging, it is important to differentiate glaucomatous rim loss from natural rim loss associated with aging. The reported rate in healthy subjects can constitute a reference database of the rate of rim area change which can be used for distinguishing between glaucomatous and age-related rim loss.