To compare empirical probability plots in patients with glaucoma for size V and III perimetry testing.
We computed empirical probability plot percentile limits after testing 60 age-matched controls tested with both size III (Swedish interactive thresholding algorithm) and size V (full threshold) perimetry twice. Probability plots of 120 patients with glaucoma tested in the same way were computed. We compared the number of abnormal test locations in the 2 stimulus sizes; we then compared these results with those from size III StatPac software (Zeiss Humphrey Systems, Dublin, California) using 2-way repeated-measures analysis of variance.
We found a similar number of abnormal test locations (P ≤ .05) for the size III and size V testing conditions identified by the probability plots (no significant difference); there were significantly fewer abnormal locations using StatPac (size III) than from our size III database. When results were stratified by mean deviation, the mild visual loss group again did not show any significant differences between sizes III and V.
Size V full-threshold testing gives a similar number of abnormal test locations in patients with glaucoma compared with the size III Swedish interactive thresholding algorithm standard test. Size V testing, with its greater dynamic range and lower variability, may be a viable alternative to size III testing in patients with glaucoma.