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Article
May 1992

Sample Size Calculations for Ophthalmologic Studies

Author Affiliations

From the Department of Preventive Medicine, University of Southern California School of Medicine, Los Angeles (Mr Gauderman); and the Departments of Biostatistics and Ophthalmology, University of Washington, and Center for Health Studies, Group Health Cooperative, Seattle (Dr Barlow).

Arch Ophthalmol. 1992;110(5):690-692. doi:10.1001/archopht.1992.01080170112036
Abstract

• Sample size calculations are shown for some common ophthalmologic study designs in which two treatments are to be compared. Included are the following three designs: 1, only one eye per subject; 2, both eyes, with each eye assigned to a different treatment; and 3, both eyes undergoing a common treatment. Continuous and binary outcomes are considered. The correlation between eyes is accounted for in the computations using a simple correction factor. For design 3, the formulas allow for a mixture of single-eye and double-eye eligible subjects. A computer program that performs the calculations is available.

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