Purpose: To determine the agreement among glaucoma specialists in assessing progressive disc changes from photographs in a cohort of patients with glaucomatous visual field loss. Design: Retrospective cohort study. Methods: Three glaucoma specialists, masked to chronological sequence, examined pairs of optic disc stereophotographs to determine whether the appearance of the optic disc had changed. Eyes for which the observers disagreed were adjudicated to reach a consensus about which discs had changed over time. Results: Sequential stereophotographs, separated in time by a median of 26 months (range, five to 50), from 164 eyes of 111 patients were analyzed. Among the three observers, the number of interpretable discs judged to have changed was 11 of 155 (7%) for Observer 1, 17 of 155 (11%) for Observer 2, and 44 of 155 (28%) for Observer 3 (κ = 0.20). Sixty-six eyes (43%) required adjudication. After adjudication, the consensus was that 10 discs had changed, six eyes in which the disc was worse in the later photograph and four eyes in which the disc was judged to appear more glaucomatous in the earlier photograph. Conclusion: Interobserver agreement among glaucoma specialists in judging progressive optic disc change from stereophotographs was slight to fair. After masked adjudication, in 40% of the cases in which the optic disc appeared to have progressed in glaucoma severity, the photograph of the "worse" optic disc was in fact taken at the start of the study. Caution must be exercised when using disc change on photographs as the "gold standard" for diagnosing open-angle glaucoma or determining its progression.
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