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Carrie K. Doyle, Trina L. Eden, Gideon J. Zamba, Chris A. Johnson, Michael Wall; Size Threshold Perimetry Performs as well as Standard Automated Perimetry with Stimulus Sizes III, V and VI for Glaucoma Detection. Invest. Ophthalmol. Vis. Sci. 2012;53(14):200.
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It is thought that large perimetric differential light sensitivity stimuli are insensitive for defect detection. To test the hypothesis that there is no difference in the total number of abnormal test locations with total deviation empiric probability plots in glaucoma patients, we compared results of glaucoma patients tested with sizes III (0.43° diameter), V (1.72°) and VI (3.44°) and size threshold perimetry (STP), a method that finds threshold by changing stimulus size.
We computed total deviation empiric probability plots from data collected by testing 60 age-matched normal participants twice using the four methods; the same normals were used for all four tests. We then analyzed the probability plots of 120 Glaucoma patients with age 66.99 ± 9.55 and mean deviation (MD) -9.53 ± 6.13 at the 42 non-blind spot locations the tests have in common. We counted the number of abnormal test locations at the 5% level and used one-way repeated measures ANOVA on ranks to compare the counts of abnormal test locations among the tests. We also stratified the results by MD (Figure).
There was a statistically significant difference in the number of abnormal test locations out of 42 among the tests: III, 26.5; V, 29.5; VI 25.9 and STP, 28.5, p = 0.001; Tukey pairwise comparisons were all statistically significant except for no significant difference in results between size V and STP. The figure shows the differences in the number of abnormal test locations flagged by the four types of probability plots stratified by MD. Size V was most sensitive, closely followed by STP. Size VI appeared slightly less sensitive (2-3 test locations in magnitude per field compared with size III) with mild glaucomatous loss (Figure).
Size V and STP provide favorable stimulus methodology for detection of mild to moderate glaucoma. Changing stimulus size can perform as well as changing stimulus luminance for disease detection. Size VI appears slightly less sensitive for glaucoma cases with mild loss.
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