Session Title: Uveitis
Session Date/Time: Saturday 19/09/2015 | 11:00-12:30
Paper Time: 11:40
First Author: : P.Carrai ITALY
Co Author(s): : F. Pichi P. Neri D. Sarraf T. Albini F. Arevalo P. Nucci
PURPOSE:The recent use of C-scan and of split spectrum amplitude OCT allows, for the first time, a new and comprehensive understanding of the physiopathological process of MEWDS.
A multicenter retrospective study.
Charts of 17 patients with findings consistent with MEWDS diagnosed according to the criteria of Jampol et al. were reviewed. In all patients, B-scan and “en-face” C-scan EDI-SD-OCT were performed at the onset of symptoms and at follow-ups with a Spectralis-HRA instrument (Spectralis HRA+OCT; Heidelberg Engineering, Heidelberg, Germany).“En-face” macular mapping was obtained with 197 transverse sections in a 5.79 × 5.79 mm2 central retinal area. The macular angiography scan covered a 3x3 mm area and comprised 200x200x8 A-scans acquired in 3.5 seconds. The flow imaging was based on split-spectrum amplitude correlation angiography (SSA), which can dissect layers of vessels in the retina and choroid.
C-scan OCT, at the level of the choriocapillaris, did not reveal enlarged hypofluorescent areas corresponding to the hypofluorescent areas on ICGA. On the contrary, the hypofluorescent areas seen on ICGA were a perfect match for hyporeflective lesions, located in the external limiting membrane, and well defined in “en-face” OCT. Swollen but intact RPE cells would likely appear thicker on OCT imaging and therefore hyporeflective on C-scan. Inflammation of the RPE cells could interrupt the orientation of photoreceptor outer segments acutely, causing an acute loss of the subfoveal IS/OS line which was detected 17/17 eyes and was completely restored in 100% of cases at 2 months follow-up. The subfoveal choroidal thickness in our patients before and after recovery decreased from x to x µm. Small hyperreflective points, located in the ganglion cell layer were identified in 8/17 eyes and could represent signs of inflammation and indicate the severity of the disease. The match between autofluorescence imaging, indocyanine green angiography, and “en-face” OCT helped identify the acute microstructural damages in the outer retina further than the choroid. In none of the 9 eyes analyzed by SSA-OCT could an alteration in the choroidal flow be visualized.
“En-face” and SSA OCT imaging offers a new conception of MEWDS lesions that may be located in the outer retina rather than the choroid. Moreover, “en-face” OCT is helpful in the follow-up of these lesions by being able to show the recovery of the outer retinal layers.