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Muhammed Alluwimi, William H Swanson; Assessment of glaucomatous defects within the macula using two different circular perimetric stimuli.. Invest. Ophthalmol. Vis. Sci. 2020;61(7):3890.
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© ARVO (1962-2015); The Authors (2016-present)
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.
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.
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.
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.
Bland-Altman analysis for the total deviation (TD) values for the size III and Gaussian stimuli. X-axis represents the average of the TD values for the two stimuli while y-axis represents the difference between them. The solid line indicates mean difference, while the dashed lines indicate the 95% limits of agreement.
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