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June 1983

Comparison of Empirically Derived and Theoretical Aphakic Refraction Formulas

Author Affiliations

From the Department of Ophthalmology, University of Illinois Eye and Ear Infirmary, Chicago (Drs Sanders and Kraff). Dr Retzlaff is in private practice in Medford, Ore.

Arch Ophthalmol. 1983;101(6):965-967. doi:10.1001/archopht.1983.01040010965024

• A formula for predicting aphakic refraction from axial length and keratometry measurements was derived from 120 cases, using linear regression analysis, as follows: Psp = 80.4 - 1.65L - 0.7K, where P indicates aphakic spectacle power in diopters; L, axial length in millimeters; and K, result of keratometry in diopters. The prediction accuracy of this simple formula was compared with that of a complex theoretic formula based on geometric optics in 205 additional cases. The prediction accuracy of the theoretic and linear regression-derived formulas was virtually identical despite their differences in complexity and derivation. The differences and similarities between theoretic-derived and regression-derived aphakic and pseudophakic prediction formulas are discussed.

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