Objective: To characterize variability in the identification of the macular center among retinopathy of prematurity (ROP) experts.
Methods: A printed set of 25 wide-angle retinal images was compiled from infants at risk for ROP using a commercially available camera. Ten recognized ROP experts were asked to mark the macular center on each image. For each image, we measured the distance from the optic disc center to the marked macular center. Distances were standardized by normalizing the horizontal optic disc diameter in each image to 0.93 mm. In images with visible peripheral disease, interexpert agreement on the presence of zone I disease was also determined.
Results: For the image with the least variability among experts, mean (SD) distance from the optic disc to the macular center was 3.69 (0.21) mm (range, 3.13-3.81 mm). For the image with the greatest variability among experts, distance from the optic disc to the macular center was 4.32 (1.19) mm (range, 3.21-7.19 mm). In 7 of 21 images (33%) with visible peripheral disease, there would have been disagreement among experts in the diagnosis of zone I disease based on identification of the macular center. Among the 10 experts, in 17 of 25 images (68%), 1 expert identified the distance between the optic disc and macular center to be greater than 1 SD from the mean.
Conclusion: Significant variability exists among experts in identification of the macular center from wide-angle images, which raises concerns about the reliability of zone I ROP diagnosis.