Fig. 1.1 Four fundus images showing a normal macula (a), confluent soft drusen (black arrows) covering the macula (b), geographic atrophy (white arrows) and soft drusen (black arrows) of the macula (c), and a choroidal

Pearl

Late AMD has two very different clinical manifestations.

Pearl

The etiology behind AMD is still unknown.

A Genetic Cause

Family Studies

neovascular membrane (black arrow heads) covering the macula with a concomitant subretinal hemorrhage (white arrow) (d) (Photographs were provided by Kang Zhang, MD, PhD, and James Gilman, CRA)

have a family history of the disease [3, 4] and first-degree relatives of patients with late AMD have a fourfold increased risk of AMD. One case control study examining the frequency of AMD in siblings of affected patients found that 25% were also affected by the disease. In control patients, only 1% of the siblings exhibited signs of AMD [5]. Twin studies have also shown familial association [6, 7], with one study reporting a 19% concordance rate among dizygotic twins, and a 37% concordance rate among monozygotic twins [8]. Strong evidence for a familial component to AMD highlights a genetic predisposition to the disease.

Associations with Race

The search for a genetic basis to AMD began with an understanding that family history is a significant risk factor. Over 20% of those with AMD

Research involving different populations has indicated that the risk of AMD varies by race. Across