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Shiri Zayit-Soudry, Nicolas Sippl-Swezey, Travis Porco, Stephanie Lynch, Reema Syed, Kavitha Ratnam, Moreno Menghini, Austin Roorda, Jacque L Duncan; Reliability of Cone Spacing Measures in Eyes with Inherited Retinal Degenerations. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2631.
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To determine short-term variability of Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO)-derived cone spacing measures in eyes with inherited retinal degenerations (IRD) and in normal eyes. This information is essential to establish the role of AOSLO as a sensitive biomarker for longitudinal tracking of photoreceptor loss during disease progression and response to treatment.
Twenty patients with IRD and 10 visually normal subjects from a larger clinical trial (NCT00254605) underwent AOSLO imaging at 2 visits separated by no more than 1 month. Cone spacing was measured in multiple macular regions in each image by 3 independent graders. Variability of cone spacing measures between visits, between graders and between eyes was determined, and correlated with standard macular measures, including visual acuity, Goldmann perimetry, and spectral-domain optical coherence tomography (SD-OCT)-derived inner/outer segment junction ,or Ellipsoid Zone (EZ), width.
Overall, cone spacing was measured in 2905 regions. Cone spacing measures were closely correlated between visits (ICC > 0.89 for both study groups). Mean relative inter-visit spacing difference (absolute difference in measures obtained at each visit divided by the mean of both measures at each region) was 0.051 for IRD eyes and 0.04 for normal eyes. Inter-grader variability was higher in eyes with IRD than in normal eyes (mean ICC = 0.807 IRD, 0.95 normal eyes), and at retinal eccentricities lower than 1 degree or greater than 3 degrees compared to regions at intermediate eccentricities. There were significant correlations of varying strength between inter-grader cone spacing agreement and macular measures of disease severity. Comparison of cone spacing measures between eyes of the same patient showed strong agreement for all subjects (ICC > 0.84 for both study groups).
We found substantial inter-visit, inter-grader and inter-ocular agreement of macular cone spacing measures in normal eyes as well as in eyes with IRD. This information establishes the repeatability of cone spacing measures for current and future clinical trials involving AOSLO imaging.
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