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Gerard McGowan, Tsveta Ivanova, David Yorston, Niall Strang, Velitchko Manahilov; Mapping visual distortions in macular disease. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3845. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a test for mapping visual distortions (metamorphopsia) within the central visual field in patients with macular disease.
Metamorphopsia testing was carried out pre- and post-operatively. The test uses octagonal grids formed by black elements (squares) of various densities (Fig. 1) These dartboard-like charts (D-charts) contain grids at eccentricities of 0.5-1.5, 1.5-3.5, 3.5-7 and 7-11.5 deg. Patients were presented monocularly with D-charts at 40 cm distance. They were instructed to look at the fixation disk in the centre of the D-charts and report if the grid appeared distorted (irregular) by indicating with their finger the sectors (45 deg apart) of apparent distortion. The metamorphopsia score (the maximal element separation which produces perception of grid distortion) was determined for each ring and sector. The results provide a two dimensional map of metamorphopsia severity.
13 patients (mean age 72; SD 8.1 years) with epiretinal membrane (ERM) and 16 patients (mean age 70; SD 7.4 years) with macular hole (MH) were tested. Mean LogMAR visual acuity for MH was 0.9 (SD 0.4) and 0.5 (SD 0.3), for ERM. Pre-operatively, mean values of total metamorphopsia score and metamorphopsia area were significantly larger than zero (p<0.05, t-tests Bonferroni corrections) in the near peripheral regions (eccentricities of 0.5-3.5 deg for ERM and 0.5-7 deg for MH). Following surgery patients showed a significant reduction in the total metamorphopsia score and in the area of metamorphopsia, even if visual acuity was unchanged.
D-Charts allow quantification of metamorphopsia severity and localization in ERM and MH patients with a wide range of visual acuities. The area of visual distortion in MH patients was greater than that for patients with ERM. The results suggest that the D chart is an effective tool to map changes in metamorphopsia pre- and post-surgically, and may be useful in selecting which patients will benefit from surgery.
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