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A.D. Realini, S.B. Flynn, J.B. Pittenger; Cup/Disc Assessment: Does the Last Nerve Examined Influence the Next Nerve Examined? . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2167.
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Purpose: To determine if, in sequential trials, optic nerves are judged independently or if each judgment is affected by the previous judgment. In other words: Am I likely to over- or under-estimate a cup/disc (C/D) ratio if I just saw a large or small cup? Methods: Photographs of 4 optic nerves with C/D ratios of 0.2, 0.4, 0.6 and 0.8 were shown to 21 ophthalmologists in a repetitive sequence such that each C/D ratio was presented following each of the other C/D ratios and itself (ie, the 0.2 nerve was shown four times, preceded once by itself and once each by the 0.4, 0.6, and 0.8 nerves, etc). Observers were asked to judge the C/D ratio of each photograph. Analysis was performed to determine if C/D judgment was influenced by the prior trial. Results: Plotting observer judgment of C/D as a function of the C/D of the preceding trial should give a horizontal line (slope = 0) if the preceding trial had no effect on judgment. In our data set, the slope of this line was 0.03 (p<0.05 by paired t-test), suggesting that C/D assessment is influenced by prior C/D assessment. Conclusions: In assessing C/D ratios, clinicians are influenced by recently-seen optic nerves. Viewing large C/D ratios leads to overestimation in subsequent C/D assessment; similarly, viewing small C/D ratios leads to underestimation.
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