The age-related eye disease study (AREDS) system for classifying cataractsfrom photographs: AREDS report No. 4

PURPOSE: To describe the system for grading cataracts from photographs in t he Age Related Eye Disease Study (AREDS). METHODS: The system for grading cataracts in AREDS uses photographs taken i n a standardized fashion with specially modified cameras at 11 clinical cen ters, The photographs are evaluated by graders for quality and cataract sev erity at a central reading center, The area of lens involvement is used to assess the severity of cortical and posterior subcapsular opacities, Optica l density of nuclear opacity is graded against a series of seven standard p hotographs. Contemporaneous variability in grading is evaluated periodicall y by having a second examiner regrade a subset of the photographs. Temporal variability is assessed by annually regrading a subset of photographs. RESULTS: Photographs of 925 eyes, most with no or early lens opacities, wer e regraded to assess intergrader reliability. For cortical opacities, there was an absolute difference of 10% or greater of area involved in 1.9% of t he replicate gradings. For posterior subcapsular opacities an absolute diff erence of 5% of area involved was noted in 2.8% of the regraded photographs . For nuclear opacities, absolute differences of 1.5 or more steps were obs erved in 0.6% of eyes. There was little evidence of temporal drift in gradi ng any of the three types of opacity during four annual regrades. CONCLUSIONS: We have demonstrated a high degree of reliability in grading t he severity of lens opacities in a large study cohort with mostly early len s changes, the type of cohort most likely to be entered in clinical trials involving cataract prevention. The Age-Related Eye Disease Study System for Classifying Cataracts From Photographs could be useful in studies where th ere is a need to standardize data collection over time and across different data collection sites. Limitations of the system include the cost of imple mentation and, currently, the limited amount of data on grading reproducibi lity for more advanced lens opacities. (Am J Ophthalmol 2001;131:167-175. ( C) 2001 by Elsevier Science Inc. All rights reserved).