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Letters
January 2013

Square Root Transformation of Geographic Atrophy Area Measurements to Eliminate Dependence of Growth Rates on Baseline Lesion Measurements: A Reanalysis of Age-Related Eye Disease Study Report No. 26

Author Affiliations

Author Affiliations: Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida (Mr Feuer and Drs Yehoshua, Gregori, Penha, and Rosenfeld); and National Eye Institute, Bethesda (Drs Chew and Ferris), and EMMES Corporation, Rockville (Drs Clemons and Lindblad), Maryland.

JAMA Ophthalmol. 2013;131(1):110-111. doi:10.1001/jamaophthalmol.2013.572

The growth of geographic atrophy (GA) over 4 years in the Age-Related Eye Disease Study (AREDS) was shown to be dependent on the baseline area of GA.1 However, 3 articles have demonstrated that the square root transformation of lesion area measurements eliminates the dependence on baseline lesion size for both the test-retest variability and the growth rates.24 This square root transformation strategy was applied to the AREDS data.

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