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Jonathan M. Holmes, David A. Leske, Laura Liebermann, Sarah R. Hatt; Quantifying Symptoms of Diplopia. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6335.
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We have previously described a revised diplopia symptom questionnaire that allows a patient to rate their diplopia on a 5-point scale (never, rarely, sometimes, often, always) and in specific positions of gaze (reading, straight ahead distance, down, right, left, up, and other). In the present study, we evaluated scoring strategies for this diplopia symptom questionnaire to allow numerical representation of diplopia severity.
147 adults with diplopic strabismus completed both the revised diplopia symptom questionnaire and the patient derived Health-Related Quality of Life (HRQOL) Adult Strabismus-20 (AS-20) questionnaire. We used the 10-item function subscale score on AS-20 as the gold standard for diplopia (0 to 100). We then assigned a range of weights to the revised diplopia questionnaire responses based on patient interpretation of these options on a visual analog scale (rarely 5-25%, sometimes 20-50%, and often 65-80%). Never was weighted as 0 and always as 100, for all algorithms. We also assigned a range of weightings to the gaze positions (from equal weighting to greater weighting of primary and reading). Combining all response option weights with all gaze position weights yielded 382,848 possible scoring algorithms. We then applied each of these algorithms to the patient responses and calculated 382,848 Spearman rank correlation coefficients comparing each algorithm with the AS-20 function subscale score, across the entire cohort of patients.
AS-20 function subscale scores ranged from 8 to 100 (median 54, quartiles 35, 75). For the 382,848 possible scoring algorithms, the correlations with the AS-20 function subscale score ranged from -0.6362 to -0.5538. The best-correlated algorithm had response option weights of 5 for rarely, 50 for sometimes, and 75 for often, and gaze position weights of 40 for straight ahead in the distance, 40 for reading, 1 for up, 8 for down, 4 for right, 4 for left, and 3 for other, totaling 100.
We have now developed a data-driven scoring algorithm for the revised diplopia questionnaire that allows diplopia symptoms to be rated from 0 to 100. Based on correlations with HRQOL, straight ahead in the distance and reading positions should be highly weighted and the response option "rarely" should receive a low weight. The questionnaire with new optimized scoring algorithm will be useful in both clinical and research settings.
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