Reproducibility of the Wisconsin cataract grading system in the Blue Mountains Eye Study.

PROBLEM To measure the inter- and intra-grader reliability of the Wisconsin cataract grading system for grading of nuclear, cortical, and posterior subcapsular cataract (PSC) in the Blue Mountains Eye Study. METHODS Random samples of lens photographs from study subjects were regraded by each grader according to the Wisconsin cataract grading system. The results were compared using quadratic weighted kappa statistics to derive measures of inter- and intra-grader reliability for the grading of nuclear (5 grades), PSC (3 grades), and cortical cataract (3 grades). RESULTS Inter-grader reliability (quadratic weighted kappa) for grading of nuclear cataract varied between 0.82 and 0.79; kappa was 0.78 for cortical cataract and 0.57 for PSC. Intra-grader reliability was slightly higher than inter-grader reliability for all three cataract types. CONCLUSION In the Blue Mountains Eye Study, the Wisconsin cataract grading system provided good reproducibility, comparable to that reported from the Beaver Dam Eye Study, endorsing its usefulness in cataract epidemiology.

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