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Niamh Wynne, Jenna Grieshop, Brian Higgins, Rachel Linderman, Joseph Carroll; Presence of a scotopic scotoma in individuals with fragmented foveal avascular zones. Invest. Ophthalmol. Vis. Sci. 2022;63(7):3783 – F0204.
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Individuals with macular-foveal capillaries (i.e., a fragmented foveal avascular zone, FAZ) have been proposed to have an anomalous distribution of macular photoreceptors, based on an absence of the typical foveal scotoma on scotopic microperimetry.1 Here we sought to replicate these findings in individuals objectively classified as having a fragmented FAZ.
14 individuals participated, 7 with fragmented FAZs and 7 with normal FAZ morphometry. Each subject had testing performed on their right eye. Five 3 × 3-mm (nominal area) angiograms were acquired with the AngioVue OCT-A system (Optovue, Inc., Fremont, CA). Two scans (1 horizontal, 1 vertical) each consisting of 304 B-scans with 304 A-scans/B-scan were acquired and co-registered to create an angiogram for analysis (AngioVue software version:2018.1.0.43). From each volume, a custom slab from inner limiting membrane to 9mm above the outer plexiform layer was extracted. Slabs from five volumes were registered and averaged using bUnwarpJ in FIJI. The presence of a fragmented FAZ was objectively determined using a previously described method.2 Scotopic microperimetry testing was performed using a MP-1S microperimeter (Nidek Technologies, Gamagori, Japan). A customized microperimetry pattern of 45 points within the central 8 degrees centered near the fovea was used, and interpolated maps of foveal sensitivity were generated from scotopic microperimetry responses. Where possible, scotoma area in deg2 was estimated using a 1db threshold.
For all participants (10 female, 4 male; aged 12-55 years) there was a central area of reduced sensitivity, though the scotoma area could only be estimated in 12 participants. The mean scotoma area in those with fragmented FAZs was 1.86 deg2 (range: 0.310-4.15 deg2), while the mean scotoma area in the normal FAZ group was 1.53 deg2 (range: 0.293-3.62 deg2). These values are consistent with histological estimates of the rod-free zone. There was no significant difference in scotoma area between individuals with normal and fragmented FAZs (p=0.42, unpaired t-test).
In contrast to previous reports, we do not observe an absence of a foveal scotoma using scotopic microperimetry in individuals with a fragmented FAZ.References:1. PMID: 312747112. PMID: 31956075
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
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