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Michael Wall, Carrie K. Doyle, Chris A. Johnson; Total Deviation Probability Plots for Stimulus Size VI Perimetry: A Comparison with Size III and V Stimuli. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5520.
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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°).
We computed empiric probability plots from data collected by testing 60 age-matched normal participants using size III and size V testing; size VI data were obtained a different age-matched set of 56 normals. We then analyzed the probability plots of 84 Glaucoma patients (age 67.7 ± 8.9, mean deviation -8.2 ± 5.0). We counted the number of test locations without (see Nl in Fig) and with loss at <1%, <2%, and <5% and < 10% levels (Fig) and compared the number of normal and abnormal test locations using sizes III, V and VI. We used one-way repeated measures ANOVA to compare the counts of normal and abnormal test locations among the tests.
The graph shows the differences in the number of normal and abnormal test locations flagged by the three types of probability plots (average of two visits). There was a significant difference (p=.001) between sizes III, V and VI but not between size V and VI for normal and < 1% values. At <10% and <5% loss, the number of abnormal test locations did not differ significantly among the tests. For the 2% cutoff, size VI was greater than size V (p=.001).
Size V and VI full threshold testing produce a smaller number of abnormal test locations in glaucoma patients, compared to size III SITA but the differences are not very clinically meaningful (2-3 stimulus locations difference per test). Size V and VI testing, with their greater dynamic range and lower variability may be viable alternatives to size III testing in glaucoma patients, particularly those with greater visual field losses.
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