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Asma Saud, Kavitha Ratnam, Jia Qin, Panagiota Loumou, Shane Griffin, Austin Roorda, Travis Porco, Jacque L. Duncan; Structural loss precedes visual acuity loss in the fovea of patients with retinal degeneration. Invest. Ophthalmol. Vis. Sci. 2016;57(12):155. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the relationship between cone spacing with clinical measures of visual acuity over time in eyes with inherited retinal degeneration (IRD).
High-resolution images of the retina were obtained using adaptive optics scanning laser ophthalmoscopy from 19 eyes of 15 IRD patients: 12 with RP, 1 with Usher syndrome type 2, 1 with Usher syndrome type 3 and 10 eyes of 5 normal subjects. These images were taken at two time points separated by greater than 300 days (mean 557 days, range 311-1935 days). From these images, cone spacing was measured from 0.02 to 0.19 degrees from the preferred retinal locus (PRL), which indicates the anatomic fovea. These values were used to compute cone spacing Z-scores, (based on 37 age-similar normal eyes). Z-scores were compared to log mean angle of resolution (log MAR) best-corrected visual acuity at each of the two time points for each subject.
Cone spacing measured within 0.19 degrees from the PRL was significantly correlated with logMAR at baseline (Spearman’s rank correlation rho=0.56, 95% confidence interval (CI) 0.29-0.78, P < 0.01, clustered bootstrap) and at follow-up (rho=0.50, 95% CI 0.09—0.77, P=0.03). Comparing longitudinal Z score values with baseline, there was a small but significant increase in Z score during follow up in the retinal degeneration patients of +0.56 (P=0.027), but there was no significant change in logMAR in patients, and no significant change in Z score or log MAR in normal eyes.
Cone spacing correlated with visual acuity in normal subjects and patients with inherited retinal degeneration. In eyes with retinal degeneration, cone spacing increased slightly but significantly during 1-5 years of follow up, although logMAR did not change significantly. These results suggest cone spacing Z score may be a more sensitive measure of cone loss at the fovea than measures of visual acuity in patients with inherited retinal degeneration.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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