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Ami Cuneo, Shiri Zayit-Soudry, Christopher Songster, Sam Arnow, Austin Roorda, Ari Green, Jacque L Duncan; High-resolution assessment of cone photoreceptor structure in patients with multiple sclerosis. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1589.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate cone structure in regions correlated with central scotomas in patients with multiple sclerosis.
Adaptive optics scanning laser ophthalmoscopy (AOSLO) was used to evaluate the structure of macular cones within 3 deg of the fovea in 2 patients with relapsing remitting multiple sclerosis (MS), each of whom had central scotomas within 3 deg of fixation due to prior episodes of optic neuritis (ON) occurring more than 7 years prior to imaging. Cone spacing was estimated using a histogram analysis of contiguous subsets of cones at locations along the horizontal and vertical meridians separated by 1 deg intervals. Cone spacing was measured at locations where cones were unambiguous, and compared with values from 27 healthy eyes. Registered spectral domain optical coherence tomography (SD-OCT) data was used to confirm retinal anatomy consistent with cone structures in analyzed regions; images were segmented to analyze the average thickness of the outer retinal (ONL+ and OS+) layers and retinal ganglion cell layer in the central 20 degrees of the macula and compared with 20 normal eyes.
Cone spacing was within the 95% confidence intervals around the normal mean at all locations where unambiguous cones were observed. In regions associated with loss of visual field sensitivity ranging from 2-21 dB, cone spacing was normal and comparable to measures from the contralateral eye at similar retinal locations with normal sensitivity. Qualitatively, cone packing and reflectivity appeared no different from normal. Although the mean retinal ganglion cell layer thickness (P = 0.008) was significantly lower than normal in eyes with a history of prior ON, the outer nuclear plus Henle’s fibers and the outer plexiform layer, and inner and outer segment layers were not significantly different from controls.
AOSLO revealed normal cone spacing and appearance throughout the macula in eyes of patients with MS with persistent central scotomas from prior episodes of ON. The findings suggest that visual deficits in patients with MS can be attributed to ganglion and inner nuclear layer injury, and demonstrate no evidence of cone loss in scotomatous regions, suggesting that trans-synaptic neuronal degeneration does not extend from the ganglion cells to the photoreceptors. The ability to assess individual cone structure and function may provide insight into mechanisms of visual loss in MS.
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