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Yi Zhai, Manlong Xu, Ioannis Dimopoulos, David G Birch, Paul S Bernstein, Peter Francis, Jenny Holt, David Kirn, Ian M MacDonald; Quantification of RPE changes in choroideremia using a Photoshop-based protocol. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6131.
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To confirm fundus autofluorescence (FAF) area as a marker for disease progression in subjects with choroideremia, and to identify a valid and reproducible method for quantifying the area of preserved retinal pigment epithelium (RPE) in choroideremia.
Thirty-six subjects were enrolled in a natural history study of patients with choroideremia (NCT02994368). Inclusion criteria included age > 14 years, confirmed CHM mutation, and vision of 20/200 or better. Spectralis SD-OCT (Heidelberg Engineering) with a 55-degree lens was used to capture images of the RPE in the macula. Images from the same eye were co-registered and aligned with i2K Align Retina software (Dual-Align LCC) imaging. A Photoshop-based image protocol was developed to allow the adjustable measurement of RPE area. By using the quick selection tool and and image analysis function, two certified graders independently defined the FAF. The results of the 2 independent gradings of FAF images were compared to assess the reproducibility of this protocol.
Results: Of the 36 patients (mean age 35.7 years, range 16-72 years) with available FAF data, 34 had finished a baseline visit, and 23 had finished a 1-year visit. For inter-grader comparison, all 114 images were included for analysis. Among them, 44 eyes of 22 patients had both baseline images and 1-year images and were included in the analysis of rate of RPE loss. The absolute difference (mean ± SD) between two independent graders for each image was 0.46 ± 0.99 mm2, and percentage difference between two independent graders was 4.01 ± 8.82%. The RPE area as determined by the 2 graders showed good agreement with an intraclass correlation coefficient of 0.980 (95% CI, 0.963-0.989; P<.001). The area of RPE in the central macula was seen to decrease significantly (P<.001) at a rate of 2.72 ± 3.86 mm2 annually, and at percentage of 7.41±5.93%.
FAF is considered as a surrogate biomarker of choroideremia progression. A Photoshop-based quantification of preserved RPE area in patients with choroideremia is feasible, and has a good reproducibility. Our data suggest that FAF area reduction may be measured with precision and accuracy in a feasible time frame for clinical trials in choroideremia patients.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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