AN INDEPENDENT EVALUATION OF THE AGE-RELATED EYE DISEASE STUDY (AREDS) CATARACT GRADING SYSTEM

Purpose. To assess intra-and interobserver reproducibility of the Age- Related Eye Disease Study (AREDS) system for grading lens opacities an d to provide data on its capacity to reliably detect changes in lens s tatus. Methods. Independent and replicate grading of 40 sets of lens p hotographs (one slit-lamp and two retroillumination photographs) were performed by three experienced observers. Patients were participants i n the Collaborative Italian-American Clinical Trial of Nutritional Sup plements which is testing the effect of a mineral-multivitamin supplem ent on age-related cataract (CTNS). Scatterplots and intraclass correl ation were used to assess measurement error. Results. Analysis reveale d good intra-and interobserver reproducibility of the system. Greatest intraobserver measurement error showed 100% of pairs within 10% areal difference for cortical cataract, 97.5% within 15%, areal difference for posterior subcapsular cataract, and 100% within 1 density unit dif ference for nuclear opacity. Greatest interobserver measurement error showed 95% of pairs within 10% areal difference for cortical cataract, 97.5% within 15% areal difference for posterior subcapsular cataract, and 97.5% within 1.5 density unit difference for nuclear opacity. Con clusions. The AREDS lens opacities grading system appears to be suffic iently reliable to detect changes of at least 10% areal involvement fo r cortical, 15% areal involvement for posterior subcapsular, and 1.0 u nits for nuclear opacities. It therefore seems sufficiently sensitive to adequately monitor progression of lens opacities in a longitudinal study of patients with early cataract. Its applicability in a populati on with advanced or complex mixed opacities must await further testing .