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Geographic Atrophy
9
Geographic atrophy (GA) is considered the late stage
of the dry form of Age-related Macular Degeneration
(AMD)
(1)
. GA is less common than neovascular AMD
and it is responsible for 10-20% of cases of legal blind-
ness in this condition
(2,6,7)
.
2. Definition
Usually defined as any sharply delineated round or oval
area of hypopigmentation, or apparent absence of the reti-
nal pigment epithelium (RPE), in which choroidal vessels
are more visible than in surrounding areas, that must be at
least 175 μm in diameter
(1)
. Other dimensions as 200 μm,
500 μm and 700 μm have been proposed as minimum
limit for GA because the regression of a single soft drusen
can be followed by a small atrophic area (Fig. 1)
(3,28)
.
1. Introduction
Author:
Fernanda Vaz, MD
Ophthalmology Department, Hospital de Egas Moniz
New University of Lisbon, Lisbon, Portugal
Figure 1. Fundus photography showing a sharply delineated area of hypopigmentation or apparent absence of RPE in both eyes of the same patient.
In Age-related Eye Disease Study (AREDS), GA is
included in category 3 or intermediate form (if not
involving the center of the macula), and 4 or advanced
form (involving the center of the macula)
(4)
.
One eye with GA and choroidal new vessels (CNV) is
considered as having exudative form
(5)
.
3. Epidemiology and risk factors
The global prevalence of GA is 0.66% in all ages but it
occurs in 0.34% between 65-74 years old, 1.3% between
75-84 and 4.4% over 85 years old. The prevalence
increases to 22% after 90 years of age
(2)
. It corresponds to
half of exudative form prevalence
(7,8,10,11)
.
The most consistent risk factors are age, familiar history
and tobacco smoking like in other forms of AMD
(2,7,10)
.
In AREDS, GA was also associated with: high BMI
(body mass index); use of calcium channel blockers and
ß-blockers; not using anti-acids; not using hormone
replacement (woman); light iris color and less education
level
(11,12)
.
The prevalence of GA is lower in blacks than in whites
