The International Classification system and the progression of age-related macular degeneration

Abstract

Purpose: To determine whether grading based on the International Classification (IC) for age-related macular degeneration (AMD) allows recognition of change during the progression of the disease.

Methods: Stereoscopic color fundus photographs of 50 eyes of 25 patients with AMD and at least 5 years of review were graded in a random and masked fashion for changes over time in the characteristics of drusen, pigmentary changes, and end-stage disease, according to the system defined by the IC for AMD, by two independent graders (F.B.S., I.L.). Fundus images were also analyzed in time sequence for clinical changes by a senior grader (I.L.) and two ophthalmologists (A.C.B., T.P.) without access to the grading forms of the IC grading. Clinical change, as recorded by the IC grading and the individual analysis, were compared.

Results: There was 97.8% (kappa = 0.70) concordance in identification of change. In four cases, the clinical classification differed from the IC grading: Two cases of drusen and two of end-stage disease grading. Inter-observer agreement for the IC grading was 89.4% for predominant phenotype (kappa = 0.84), 89.36-91.49% for presence of choroidal neovascularization (CNV) (kappa = 0.79-0.83), 87.23-89.36% for geographic atrophy (GA) (kappa = 0.62-0.74) and 55.32% for area covered by drusen (kappa = 0.31).

Conclusions: Overall, progression from earlier stages of AMD to either of the two forms of advanced AMD were reflected accurately by the IC grading in the vast majority of cases.