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M. F. Chiang, P. J. Thyparampil, D. Madigan; Interexpert Agreement in Identification of Zone 1 Disease in Retinopathy of Prematurity. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3144.
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To measure agreement in identification of the macular center among retinopathy of prematurity (ROP) experts. Zone 1 of the retina extends from the optic disc center to twice the distance to the macular center. This must be diagnosed accurately and reproducibly because the Early Treatment for ROP study showed that zone 1 is a defining feature of severe disease that requires treatment or close follow-up.
A printed set of 25 wide-angle retinal images was compiled from infants with ROP, using a commercially available device (RetCam II; Clarity Medical Systems, Pleasanton, CA). Nine recognized ROP experts were asked to mark the macular center on each image. For each image, the distance from the optic disc center to the marked macular center was measured. Distances were standardized by normalizing the horizontal optic disc diameter in each image to 1.05 mm. In images with visible peripheral disease, interexpert agreement on presence of zone 1 disease was also determined.
For the image with best interexpert agreement, mean (SD, range) distance from the optic disc to the macular center was 4.143 (0.253, 3.515-4.275) mm. For the image with worst interexpert agreement, mean (SD, range) distance from the optic disc to the macular center was 4.893 (1.414, 3.61-8.05) mm (Figure). In 5/25 (20%) images, there was disagreement among experts in diagnosis of zone 1 disease based on identification of the macular center. One expert identified the distance between the optic disc and macular center to be greater than 1 SD from the mean among the 9 experts in 17/25 (68%) images.
Interexpert agreement in identification of the macular center from wide-angle images is imperfect. This may have important clinical consequences.
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