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Q. Chen et al.
the early and late stages. Generally, the late AMD can be further divided into ‘wet’
(neovascular) and ‘dry’ (atrophy) forms. Recent researches indicate that neovascular
AMD account for two-thirds of the late cases, while one-third are atrophic. Early
AMD, defined by the development of large drusen or pigment changes at the macula
may be associated with either no vision loss or early changes in reading central vision.
Late AMD includes both neovascular AMD and geographic atrophy, in a ratio of
about 2:1. Neovascular (‘wet’ or exudative) AMD is characterised by the appearance
of blurring of the central vision and distortion with straight lines appearing crooked
or wavy, with or without a dark or blank patch. Perception of colours is also often
affected. Geographic Atrophy (‘dry’ AMD) reduces capacity for near visual tasks
as central vision becomes severely impaired. Note that some people include ‘early
AMD’ within the category of ‘dry AMD’. About 1.75 million U.S. residents currently have advanced age-related macular degeneration with associated vision loss,
with that number expected to grow to almost 3 million by 2020 [3]. In this chapter,
our main focus is on drusen and geographic atrophy of the AMD diseases.
11.1.1 Drusen
With age, one change that occurs within the eye is the focal deposition of acellular,
polymorphous debris between the retinal pigment epithelium and Bruch’s membrane.
These focal deposits, called drusen (Fig. 11.1a), are observed during funduscopic
examination as pale, yellowish lesions and may be found in both the macula and
peripheral retinal [4]. Drusen are categorized as small (<63 µm in diameter), medium
(63–124 µm), or large (>124 µm) on the basis of studies that classified the grade
of age-related macular degeneration [5]. Drusen are also categorized as hard or soft
on the basis of the appearance of their margins. Hard drusen have discrete margins;
conversely, soft drusen generally have indistinct edges, are usually large, and can
be confluent [6]. Most patients who develop severe visual loss from AMD have
this exudative stage. These fundus changes may predispose the eye to develop the
neovascular/exudative stages of AMD. Treatment for AMD has been shown to be
effective for only a small proportion of patients who have a well-defined choroidal
neovascular membrane (CNVM) more than 200 µ from the foveal center. Even in
successfully treated cases, severe visual loss is postponed only for about 18 months
because of the high rate of recurrent CNVMs that extend into the fovea. Thus, despite
recent breakthroughs in laser treatment for AMD, most patients who develop the
exudative form of AMD will develop central visual impairment [7].
11.1.2 Geographic Atrophy
Geographic atrophy is the advanced (late) form of dry AMD (Fig. 11.1b). Here,
atrophy refers to the degeneration of the deepest cells of the retina. These are cells
Q. Chen et al.
the early and late stages. Generally, the late AMD can be further divided into ‘wet’
(neovascular) and ‘dry’ (atrophy) forms. Recent researches indicate that neovascular
AMD account for two-thirds of the late cases, while one-third are atrophic. Early
AMD, defined by the development of large drusen or pigment changes at the macula
may be associated with either no vision loss or early changes in reading central vision.
Late AMD includes both neovascular AMD and geographic atrophy, in a ratio of
about 2:1. Neovascular (‘wet’ or exudative) AMD is characterised by the appearance
of blurring of the central vision and distortion with straight lines appearing crooked
or wavy, with or without a dark or blank patch. Perception of colours is also often
affected. Geographic Atrophy (‘dry’ AMD) reduces capacity for near visual tasks
as central vision becomes severely impaired. Note that some people include ‘early
AMD’ within the category of ‘dry AMD’. About 1.75 million U.S. residents currently have advanced age-related macular degeneration with associated vision loss,
with that number expected to grow to almost 3 million by 2020 [3]. In this chapter,
our main focus is on drusen and geographic atrophy of the AMD diseases.
11.1.1 Drusen
With age, one change that occurs within the eye is the focal deposition of acellular,
polymorphous debris between the retinal pigment epithelium and Bruch’s membrane.
These focal deposits, called drusen (Fig. 11.1a), are observed during funduscopic
examination as pale, yellowish lesions and may be found in both the macula and
peripheral retinal [4]. Drusen are categorized as small (<63 µm in diameter), medium
(63–124 µm), or large (>124 µm) on the basis of studies that classified the grade
of age-related macular degeneration [5]. Drusen are also categorized as hard or soft
on the basis of the appearance of their margins. Hard drusen have discrete margins;
conversely, soft drusen generally have indistinct edges, are usually large, and can
be confluent [6]. Most patients who develop severe visual loss from AMD have
this exudative stage. These fundus changes may predispose the eye to develop the
neovascular/exudative stages of AMD. Treatment for AMD has been shown to be
effective for only a small proportion of patients who have a well-defined choroidal
neovascular membrane (CNVM) more than 200 µ from the foveal center. Even in
successfully treated cases, severe visual loss is postponed only for about 18 months
because of the high rate of recurrent CNVMs that extend into the fovea. Thus, despite
recent breakthroughs in laser treatment for AMD, most patients who develop the
exudative form of AMD will develop central visual impairment [7].
11.1.2 Geographic Atrophy
Geographic atrophy is the advanced (late) form of dry AMD (Fig. 11.1b). Here,
atrophy refers to the degeneration of the deepest cells of the retina. These are cells