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Adam M Dubis, Jasleen Kaur Jolly, Lyndon daCruz, Mariya Moosajee, Robert E MacLaren; Assessing Residual Photoreceptor Morphology in Choroideremia. Invest. Ophthalmol. Vis. Sci. 2020;61(7):819.
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Choroideremia (CHM) is an X-linked progressive retinal degeneration. Several treatment trials are now underway, achieving varying success. These results have prompted questions underlying effective variability and what part of structural variability may exist to help explain treatment effectiveness. Previous reports of cone structures in Choroideremia have been equally ambiguous with studies using fundus based and confocal cellular imaging suggesting normal cone densities but non-confocal methods suggesting variability at the edge with normal density within the area of intact ellipsoid zone.
Subjects were recruited from two on-going trials at Moorfields Eye Hospital and Oxford Eye Hospital. Subjects underwent short-wavelength autofluorescence (SWAF) and AOSLO imaging using a custom built device with confocal and non-confocal imaging capabilities. AOSLO imaging was performed to the residual AF island edges where possible with AOSLO and AF images registered to assess cone morphology in continuous and mottled regions of AF signal. Ten subjects without retinal degeneration were imaged to assess localised variability in cone density.
Forty-four subjects (age 18-52) were recruited with 40 mosaics of sufficient quality to judge photoreceptor morphology across the mosaic. In 24/40 subjects both continuous and mottled AF regions can be seen. Localised reduction in cone density was observed in areas of mottled but not continuous AF signal in 31/40 mosaics. Two cone loss phenotypes were observed. Twenty-one patients had localised regions of swollen photoreceptors with a reduction of 13.2% (range: 6-30%) compared to adjacent areas. The second phenotype was localised loss without swelling, present in 29/40 patients, here density was reduced by 22.3% (range: 10-45%) compared to adjacent areas. Some but not all areas of reduced density spatially segregated to dark regions of mottled AF. Some patients had both phenotypes (6/40). Localised difference in the normal cohort was 0.9% (range: 0.3-2.1%).
Patients with choroideremia have variable cone density in areas of mottled AF, even away from the edge of degeneration. Better characterising this phenotype and assessing how it affects tests such as microperimetry will provide added insight to understanding current clinical trials and planning future interventions.
This is a 2020 ARVO Annual Meeting abstract.
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