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Paul S Micevych, Jessica Wong, Hao Zhou, Ruikang K Wang, Travis Porco, Austin Roorda, Jacque L Duncan; Cone structure and function in RPGR- and USH2A-associated retinal degenerations. Invest. Ophthalmol. Vis. Sci. 2022;63(7):4530 – F0317.
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© ARVO (1962-2015); The Authors (2016-present)
Variants in genes whose products are expressed at the photoreceptor connecting cilium, including RPGR and USH2A, are common causes of rod-cone degeneration. We compared cone structure and function between RPGR- and USH2A-associated retinal degenerations.
This single-center, cross-sectional study included 13 eyes (9 subjects) with RPGR-related X-linked retinitis pigmentosa (RPGR), 16 eyes (9 subjects) with USH2A-related autosomal recessive retinitis pigmentosa (ARRP), 15 eyes (10 subjects) with USH2A-related Usher syndrome type 2 (USH2), and 5 healthy eyes (4 subjects). Structural measures included cone density from adaptive optics scanning laser ophthalmoscopy (AOSLO) and photoreceptor inner segment (IS), outer segment (OS) and outer nuclear layer (ONL) thickness from optical coherence tomography (OCT) images. Cone function was assessed by macular integrity assessment (MAIA) microperimetry. OCT angiography (OCTA) images were used to study choriocapillaris flow deficit percent (CCFD%), using the area ratio of flow deficits greater than one mean standard deviation from a normal database. Measures were compared at designated regions (Figure 1) through ANOVA with pairwise comparisons among disease groups, adjusted for disease duration and region eccentricity.
Comparisons to healthy eyes revealed lower cone density in RPGR and USH2 (p=0.02, p=0.04), shorter OS in RPGR and USH2 (p=0.0001, p=0.047), shorter IS in RPGR (p=0.004), thinner ONL in RPGR (p=0.008), and reduced macular sensitivity in RPGR, USH2, and ARRP (p=0.008, p=0.0498, p=0.04). OS were shorter in RPGR than either USH2 (-16.8 μm, p=0.01) or ARRP (-21.2 μm, p=0.001; Figure 2). IS were shorter in RPGR than USH2 (p=0.03). ONL was thinner in RPGR than either USH2 (p=0.03) or ARRP (p=0.03). Mean CCFD% was greater in RPGR than USH2 (p=0.02).
Differences in outer retinal thickness and CCFD% reveal more advanced structural and vascular alteration in RPGR than USH2A-related retinal degenerations. Similarities in macular sensitivity suggest comparable levels of cone dysfunction in these retinal degenerations.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
Figure 1. USH2 fundus photo (A) with serial overlay of OCT scan (B), OCTA choriocapillaris flow deficit map (C), MAIA sensitivity map (D), and AOSLO confocal montage (E) with regions of interest (red).
Figure 2. Comparisons in outer segment thickness (RPGR-USH2 p=0.01, RPGR-ARRP p=0.001, RPGR-Normal p=0.0001, USH2-Normal p=0.047).
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