A simplified severity scale for age-related macular degeneration: AREDS Report No. 18

Abstract

Objective: To develop a simplified clinical scale defining risk categories for development of advanced age-related macular degeneration (AMD).

Methods: Following development of a detailed scale for individual eyes based on gradings of fundus photographs in the Age-Related Eye Disease Study, rates of progression to advanced AMD were assessed in cross-tabulations of presence or absence in each eye of 2 easily identified retinal abnormalities, drusen and pigment abnormalities. Large drusen and any pigment changes were particularly predictive of developing advanced AMD.

Results: The scoring system developed for patients assigns to each eye 1 risk factor for the presence of 1 or more large (> or = 125 microm, width of a large vein at disc margin) drusen and 1 risk factor for the presence of any pigment abnormality. Risk factors are summed across both eyes, yielding a 5-step scale (0-4) on which the approximate 5-year risk of developing advanced AMD in at least one eye increases in this easily remembered sequence: 0 factors, 0.5%; 1 factor, 3%; 2 factors, 12%; 3 factors, 25%; and 4 factors, 50%. For persons with no large drusen, presence of intermediate drusen in both eyes is counted as 1 risk factor.

Conclusion: This simplified scale provides convenient risk categories for development of advanced AMD that can be determined by clinical examination or by less demanding photographic procedures than used in the Age-Related Eye Disease Study.

Figures

Figure 1

Fundus photograph to illustrate drusen size. In the 8-o’clock meridian, about 1 disc diameter from the center of the macula, there is a large druse, slightly larger than the minimum required to meet the greater than or equal to 125 μm (width of an average large vein at the disc margin) definition. At 5:30, near the edge of the photograph, there is an intermediate druse, defined as greater than or equal to 63 μm but less than 125 μm in diameter.

Figure 2

Risk factor scoring for patient with large drusen and pigment abnormalities in both eyes.

Figure 3

Fundus photograph of an eye with 2 risk factors (large drusen and pigment abnormalities).

Figure 4

Risk of progression to advanced age-related macular degeneration (in at least one eye in patients with both eyes at risk) based on repeated-measures logistic repression analysis of 4710 Age-Related Eye Disease Study participants, by simplified risk score assigned at baseline.

Figure 5

Risk of progression to advanced age-related macular degeneration (in at least one eye in patients with both eyes at risk) based on repeated-measures logistic regression analysis of Age-Related Eye Disease Study (AREDS) participants randomized to the AREDS combined treatment group (antioxidants plus zinc [AZ]) or placebo (P), by simplified risk score assigned at baseline.

Figure 6

Approximate 5-year rates of progression to advanced age-related macular degeneration.