Abstract
Purpose :
Perimetric testing is used to assess glaucomatous defects; and most often uses Goldmann circular stimuli with sharp edges. Studies have reported that within 10° of fixation the Goldmann size III stimulus is larger than the critical area; therefore perimetric defects will on average be less deep. Our lab authored a study showing that, at the nasal visual field (temporal raphe), a Gaussian blob stimulus with blurred edges and 0.5° standard deviation (SD) yielded deeper defects than a circular stimulus of similar size (Goldmann size V). In the current study, we tested the hypothesis that within 10° of fixation, a smaller stimulus with blurred edges (Gaussian blob with SD of 0.25°) would yield deeper defects than Goldmann stimulus size III.
Methods :
Fifteen patients with perimetric glaucomatous defect at the macula were recruited (ages 61 to 81 years). All patients were tested, one eye for each, with the size III stimulus and a Gaussian blob stimulus with SD of 0.25°, using the 68 10-2 locations. Total deviation (TD) was computed as difference from means for age-similar controls. To assess agreement on defect depth for the two stimuli, Bland-Altman analysis was used. Similar ranges were obtained for both sets of TD, by defining a floor (lowest TD) at − 1.3 log unit and a ceiling (highest TD) at + 0.3 log unit.
Results :
Bland-Altman analysis found a mean difference of 0.09 log unit in depth of defect for the size III stimulus versus the Gaussian blob stimulus. Linear regression of difference versus mean found a small but statistically significant increase in the difference for deeper defects (r = 0.15, p <0.001), with 95% limits of agreement of ±0.61 log unit. Perimetric defects, on average, were increasingly deeper for the size III stimulus.
Conclusions :
We found that, within 10° fixation, the size III stimulus on average yielded deeper perimetric defects than a similar-size Gaussian blob stimulus. This is inconsistent with a prior finding using larger stimuli in the nasal visual field. We infer that the prior finding may be limited to larger stimuli.
This is a 2020 ARVO Annual Meeting abstract.