Four-point scale developed to simplify AMD risk assessment

KOLOA, Hawaii — A four-point scale may simplify the task of assessing patients' risk for developing advanced age-related macular degeneration, according to a speaker here.

Frederick L. Ferris III, MD, discussed a simple four-point scale for evaluating advanced AMD risk at the Hawaiian Eye 2007 meeting.

Image: Singer H, OSN

"I think this is an easy technique to remember and really helpful in talking to your patients," said Frederick L. Ferris III, MD, speaking at the Retina 2007 meeting, held in conjunction with Hawaiian Eye 2007.

Dr. Ferris said the scale was developed from the Age-Related Eye Disease Study (AREDS) clinical severity scale for AMD, which he described as being "great for research but clinically difficult or impossible."

"The primary goal of the AREDS study was to collect epidemiologic information to understand the disease," he said. While the scale used in that study is useful for research, it is not clinically useful, he said.

Dr. Ferris and colleagues set out to create a simpler way of identifying patients at high risk for developing advanced AMD. The researchers began with the complex nine-step, 5-year progression scale developed for AREDS and, focusing on simple clinical features, reduced it to a five-step, four-point model.

The new four-point model focuses on large drusen, defined as drusen greater than 125 µm in diameter, approximately equal to the width of a vein at the disc margin. It also considers definite pigmentary changes as a clinical feature, Dr. Ferris said.

"In the AREDS scale you had to grade hyperpigmentation, but we just wanted to know if there was pigmentation change or not" for the new scale, he said. "If there was pigmentation change, there's hyperpigmentation."

Based on these factors, each eye is evaluated separately and the score for both eyes is totaled. One point is counted if large drusen are present and one point for pigment changes, for a possible total score of four points for both eyes combined. Patients with a total score of four points have a 50% risk of developing advanced AMD over 5 years.

Patients with a total score of three points have a 25% chance, those with a score of two have a 12% chance and those with a score of one have a 0.5% chance, Dr. Ferris said.

"These results are well within confidence intervals," he said.

For patients with advanced AMD in one eye, he said that eye is scored as two points and the other eye is scored as usual. "If both eyes have extensive intermediate drusen, score each eye as a half point," he said.

The scale could potentially be used in future clinical trials as an eligibility tool, he suggested.