Size threshold perimetry performs as well as conventional automated perimetry with stimulus sizes III, V, and VI for...

It is thought that large perimetric stimuli are insensitive for demonstrating visual field defects. 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 derived normative limits for total deviation probability plots using the second test from 60 age-matched normals. We analyzed the probability plots of 120 glaucoma patients (mean deviation was -9.3 ± 6.1 dB with a range of -0.2 to -31.6) at the 42 nonblind spot locations common to the tests. We compared the number of abnormal test locations at the 5% level among the tests using one-way repeated measures ANOVA on ranks. We stratified the results by mean deviation.

There was a statistically significant difference in the number of abnormal test locations among the tests: III, 28.5; V, 29.7; VI, 27.0; and STP, 28.8, P = 0.001; Tukey pairwise comparisons were statistically significant for the assessments between sizes V and VI and between STP and size VI. When stratifying by mean deviation, with mild visual loss, size V was most sensitive, followed by STP; size VI appeared slightly less sensitive.

Size V and STP provide favorable stimulus methodology for detection of mild to moderate glaucoma. Size VI appears slightly less sensitive for glaucoma with mild loss.