AMD severity scale helps chart risk of progression

A severity scale for age-related macular degeneration based on fundus photographs may be helpful in assessing patients’ level of risk for disease progression, investigators said. Progression along the scale may be useful as a surrogate for progression to advanced AMD, according to a report from the Age-Related Eye Disease Study Group.

The researchers developed a nine-step severity scale, combining a six-step drusen area scale with a five-step pigmentary abnormality scale. On this scale, the 5-year risk of advanced AMD increased progressively from less than 1% in step 1 to about 50% in step 9, the researchers said.

The scale was developed based on analysis of stereoscopic color fundus photographs taken at baseline, at a 2-year follow-up visit and annually thereafter of 3,212 participants in the Age-Related Eye Disease Study (AREDS). Photos were graded for drusen characteristics, including size type and area; pigmentary abnormalities, including increased pigment, depigmentation and geographic atrophy; and presence of abnormalities characteristic of neovascular AMD.

Advanced AMD was defined in the study as the presence of one or more neovascular AMD abnormalities, photocoagulation for AMD or geographic atrophy involving the center of the macula.

The AREDS researchers evaluated the associations between the severity of drusen characteristics and pigmentary abnormalities of participants’ right eyes at baseline and their development of advanced AMD within 5 years’ follow-up.

Of the 334 eyes that showed at least a 3-step progression on the scale between baseline and final follow-up, about 50% showed a stepwise progression through intervening severity levels at intervening visits, the researchers found. Repeated gradings resulted in agreement within one step on the scale in 87% of eyes.

The study is published in the November issue of Archives of Ophthalmology.