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Sarah Mrejen, Taku Sato, Richard Spaide; Assessing the Mosaic of Cone Photoreceptors Overlying Subretinal Drusenoid Deposits in vivo Using Adaptive Optics. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1742.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the cone photoreceptor mosaic in eyes with pseudodrusen as evidenced by the presence of subretinal drusenoid deposits (SDD) using adaptive optics (AO) imaging integrated into a multimodal approach.
Consecutive patients with pseudodrusen were examined using near-infra-red reflectance (IR) confocal scanning laser ophthalmoscopy (SLO) and eye-tracked spectral-domain optical coherence tomography (SD-OCT) and a flood-illuminated retinal AO camera prototype (rtx-1, Imagine Eyes, Orsay, France). The AO images were acquired between 1 and 5 degrees of retinal eccentricity from the foveal center in the areas of SDD. Correlations were made between the IR SLO, SD-OCT and the AO images. Cone packing density analysis was performed on AO images within 50 x 50 µm windows in 5 regions of interest overlying and in 5 located between SDD. Five patients with soft drusen were evaluated as a comparison group.
The mean age of 5 patients, all female, with SDD was 71.8 years. The SDD identified by combined IR and eye-tracked SD-OCT corresponded to well-defined areas darker than the surrounding uninvolved areas in the AO images. The mean (±SD) cone packing density was 1254 (± 673) cones/mm2 on SDD and 10818 (±1860) cones/mm2 between SDD. Cone density on SDD was approximately 11% of cone density between SDD, whereas cone density on soft drusen varied from 60 to 90% of cone density between soft drusen. The cone density between SDD was not significantly different from the cone density between soft drusen at the same degree of retinal eccentricity. The lack of visualization of cones on SDD was correlated with the disruption of the ellipsoid zone on corresponding SD-OCT. The cone mosaic was well preserved on soft drusen when the ellipsoid zone was preserved on corresponding SD-OCT.
The lack of visualization of cones on SDD in the AO images can be due to several possible causes: a change in their orientation, absence or shortening of their outer segments, or absence of the cones. Whether the lack of detection of cones on SDD is due to absent or shortened outer segment or absence of cones, all of these explanations imply decreased cone function is possible. These findings suggest these patients with pseudodrusen may experience decreased retinal function independent of choroidal neovascularization or retinal pigment epithelium atrophy.
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