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 degrees 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%; kappa=0.26-0.63) and intermediate soft drusen (76-94%; kappa=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%; kappa=0.60-0.95) and substantial to almost perfect for the presence of choroidal neovascularization (84-100%; kappa=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.