To compare, in eyes with an idiopathic epiretinal membrane (ERM), photoreceptor cell structural abnormalities identified on high-resolution images obtained by adaptive optics scanning laser ophthalmoscopy (AO-SLO) with the severity of metamorphopsia and anatomic findings on spectral-domain optical coherence tomography (SD-OCT).
Observational case series.
Twenty-five eyes of 24 patients with idiopathic ERM and 20 normal eyes of 20 volunteer subjects.
All participants underwent a full ophthalmologic examination, SD-OCT, and imaging with an original prototype AO-SLO system that incorporated liquid crystal-on-silicon technology. In eyes with ERM, M-CHARTS results were used to quantify metamorphopsia.
Cone mosaic patterns on AO-SLO images and metamorphopsia severity.
In normal eyes, AO-SLO images showed a regular photoreceptor mosaic pattern. In 24 (96%) of 25 eyes with ERM, "microfolds" (multiple thin, straight, hyporeflective lines in the photoreceptor layer) were identified on AO-SLO images; microfolds were not seen in normal eyes. Individual microfolds were approximately 5 to 20 μm wide, which is narrower than retinal folds seen in fundus photographs (>50 μm). Amsler charts revealed metamorphopsia around the fixation point in 12 of 13 eyes with microfolds in the fovea on AO-SLO but in none of 5 eyes without microfolds in the fovea (P < 0.001). Compared with eyes without foveal microfolds, eyes with foveal microfolds had more severe metamorphopsia (M-CHARTS distortion) in both horizontal and vertical lines (P < 0.001 for both) and greater average foveal thickness detected by SD-OCT (P=0.010). Voronoi analysis revealed that smaller numbers of cones in eyes with ERM had 6 neighbors, compared with normal eyes (P < 0.001). In eyes with ERM, average foveal thickness measured by SD-OCT correlated with visual acuity (P=0.001) and metamorphopsia scores, both horizontal (P=0.002) and vertical (P < 0.001), but visual acuity, metamorphopsia scores, and average foveal thickness were not related to SD-OCT findings of disruption in the photoreceptor inner and outer segment junction.
Adaptive optics scanning laser ophthalmoscopy images in eyes with ERM showed abnormal cone mosaic patterns, described as microfolds in the foveal photoreceptor layer. The presence of microfolds was associated with metamorphopsia, suggesting that microfolds may be involved in the formation of metamorphopsia.