Abstract
Abstract: :
Purpose:To determine the influence of chronology on optic disc stereo-photograph assessment for glaucomatous change. Methods:Interpretable stereo-photographs of the optic discs of 83 patients enrolled in the AGIS and CIGTS studies from Wills Eye Hospital were retrospectively evaluated. All cases had a follow up of at least 5 years with baseline and follow-up photographs. Three observers (1 glaucoma attending and 2 glaucoma fellows) evaluated the stereo-photographs in chronological order to identify the clinical impression of glaucomatous change (worse, stable or better) based on information such as rim width, nerve fiber layer defects, rim color, peripapillary atrophy, disc hemorrhages and blood vessel alterations. Three months later the order of the two photo pairs were shuffled and the same observers were masked to the chronological sequence. The photos were re-evaluated to determine if there was glaucomatous change. Agreement between the two readings was measured for each observer individually and for the three observers collectively. The difference between the number of photo pairs identified as worse when chronological order was known versus unknown was evaluated using a chi-square test. Results:Overall intra-observer agreement was 61%, 64% and 71% for the three observers respectively and 65% for the three observers combined. Agreement in identifying change (either better or worse) was 59%, 70% and 68% for each observer, and 66% for the three observers combined. Agreement in identifying stability was 63%, 62% and 73% respectively and 66% for the three observers combined. When the chronology was known, the number of photos graded by three observers was 101 as worse, 147 stable, and 9 better, but when the chronology was masked, 54 were identified as worse, 173 as stable, and 22 as better. The number of cases identified as worse was significantly higher when the observer knew the chronological order (p=0.007). Conclusion:Mean intra-observer agreement was 65%. Knowledge of chronology of the optic disc photos influences the designation of optic discs as glaucomatous. Chronological information likely creates an expectation bias that improves sensitivity at the cost of increased false positives.
Keywords: 498 optic disc • 359 clinical research methodology • 356 clinical (human) or epidemiologic studies: systems/equipment/techniques