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David G Birch, Lassana Samarakoon, Laura E Bocchino, B. Michele Melia, Jacque L Duncan, Allison Ayala, Isabelle Audo, Janet K Cheetham, Todd Durham, Alessandro Iannaccone, Mark E Pennesi, Katarina Stingl; Dark-adapted visual fields (DAVF) in patients with two disease-causing variants in USH2A. Invest. Ophthalmol. Vis. Sci. 2021;62(8):3241.
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© ARVO (1962-2015); The Authors (2016-present)
To identify and measure rod-mediated visual field thresholds using two-color dark-adapted chromatic (DAC) perimetry in a subset of participants in the RUSH2A study, determine the percentage of participants that retain rod function, and explore the relationship between dark adapted visual fields (DAVF) from DAC perimetry and parameters of rod function from electroretinogram (ERG) and full-field stimulus thresholds (FST).
At 6 sites, participants from the Rate of Progression of USH2A-related Retinal Degeneration (RUSH2A) 4-year natural history study of Usher syndrome type 2 (USH2) and non-syndromic autosomal recessive retinitis pigmentosa (ARRP) were invited to participate in the DAVF ancillary study. Dark-adapted retinal sensitivity was tested using cyan and red test protocols on the DAC perimeter (Medmont), and loci where cyan relative to red sensitivity was > 5 dB were considered rod mediated. Measures of full-field rod mean sensitivity, number of rod loci, maximum sensitivity, DAVF full-field hill of vision (DAVF VTOT), and 30-degree hill of vision (DAVF V30) were determined. Correlations between DAVF measures and standard clinical measures were estimated, as were kappa statistics (κ) for agreement between DAVF and other modalities regarding evidence of rod function.
49 participants (55% female, 95% white) were screened for DAVF rod function; 38/49 (78%) were found to have evidence of rod function. For comparison, 15/49 (31%) had measurable rod ERGs. For those 40 years of age or older, 7 with unmeasurable ERGs retained some rod visual field. DAVF maximum sensitivity was highly correlated with FST white thresholds (ρ=-0.80, p ≤0.001). DAVF mean sensitivity, DAVF VTOT, and DAVF V30 were more moderately correlated with FST white thresholds (ρ=-0.71, -0.72, and -0.61, respectively; all p ≤0.001). Agreement regarding evidence of rod function with DAVF was relatively poor for both FST white (κ=0.35, 95% CI= [0.14,0.57]) and ERG Rod B-Wave (κ=0.16, 95% CI= [0.004,0.31]).
Our results suggest rod-mediated function is present in many patients with symptomatic USH2A-related retinal degeneration, including many without measurable rod ERGs. FST and DAVF represent two potential measures of rod function suitable for longitudinal measures in clinical trials for inherited retinal degenerations.
This is a 2021 ARVO Annual Meeting abstract.
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