Inter- and intra-observer variability in grading lesions of age-related maculopathy and macular degeneration

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Abstract
Purpose. To introduce a revised version of the grading system established by the International ARM Epidemiological Study Group for identifying and quantifying abnormalities of age-related maculopathy (ARM) and age-related degeneration (AMD) and to investigate its reliability, specifically the inter- and intra-observer variability. Methods. Fifty eyes of 25 patients with ARM or AMD in at least one eye were randomly selected from a large ongoing collection of clinical data and DNA in a tertiary referral UK population. Stereoscopic color fundus photographs were taken with a 30° fundus camera and were centered on the macula. Presence and severity of fundus abnormalities in ARM and AMD were graded using a grid to define macular subfields and standard circles to define the size of lesions. Inter-observer variability was assessed by having three retinal specialists evaluate the color slides and intra-observer variability by re-grading the same set. Results. The inter-observer agreement for all subfields was fair to substantial for small hard drusen (70–89%; κ=0.26–0.63) and intermediate soft drusen (76–94%; κ=0.27–0.69). Agreement ranged between 87% and 100%, between 50% and 92%, and between 78% and 100% for larger drusen, the presence of hyperpigmentation, and the presence of hypopigmentation, respectively. Agreement was moderate to almost perfect for the presence of geographic atrophy (88–98%; κ=0.60–0.95) and substantial to almost perfect for the presence of choroidal neovascularization (84–100%; κ=0.62–1.00). The intra-observer variability for the grading of drusen characteristics and pigmentary changes was similar in magnitude, but slightly greater for features of advanced AMD. Conclusion. Reproducibility was achieved using a revised version of the grading system established by the International ARM Epidemiological Study Group. This grading system may therefore be used for phenotyping of ARM and AMD.