Abstract
Purpose :
We have found that glaucomatous perimetric defects can show good agreement with structural defects, and that an elongated sinusoidal stimulus can be oriented based on structural defects to identify scotomas. Here we extend this finding, by testing angioscotomas in healthy eyes.
Methods :
Right eyes of healthy adults were tested with a DLO (Digital Light Ophthalmoscope, Aeon Imaging, Bloomington IN) which gathered fundus images during stimulus presentation to allow registration of eye movements. The first stimulus was the size III perimetric stimulus (circle at top in Figure 1). Thresholds were measured at 247 locations locations in a 13 x 19, 0.5°-interval grid from 11° to17° horizontally, and -3° to +6° vertically. A ZEST algorithm used 6 trials to estimate contrast threshold at each location. The fundus images were used to infer retinal stimulus location on each trial. Three custom stimuli were developed, each being the first derivative of a Gaussian (D1) times an orthogonal Gaussian: “Small” had peak spatial frequency of 1.0 cycle/deg (cpd) and orthogonal standarddeviation (SD) = 1°; “Medium”, had peak 1.0 cpd and SD = 2°; “Large” had peak 0.25 cpd and SD = 4°. Each D1 stimulus was used to measure contrast threshold at 33 locations in an 11x3, 0.5°-interval grid from 11° to 16° horizontally and 4° to 5° vertically, chosen on the basis of size III results and anatomical information.
Results :
Findings for one participant are shown; the same pattern was observed for the other participants. When the size III stimulus had Weber contrast > 200% it was seen unless it fell on the optic disc, a region between the disc and the vasculature, or on larger vessels (Fig. 1, bottom). When maximum likelihood estimation was used to estimate contrast sensitivity for local regions, an angioscotoma was seen with an orientation near -45° (Fig. 2, top). The D1 stimuli were therefore oriented at -45°, and results were plotted as “defect depth” (Fig. 2, bottom). Locations in color have contrast sensitivity below the mean contrast sensitivity for that retinal region. All three stimuli revealed a scotoma.
Conclusions :
We confirmed our prior finding that oriented sinusoidal stimuli can be effective for identifying mild scotomas, and extended it to larger stimuli. The use of oriented stimuli holds promise for structure-guided perimetry, and results are consistent with our models of cortical pooling.
This is a 2021 ARVO Annual Meeting abstract.