- 1.
What is age-related macular degeneration?
Age-related macular degeneration (ARMD) is the leading cause of significant, irreversible central visual loss in the Western world. It is characterized by age-dependent alterations in the sensory retina, retinal pigment epithelium, and choriocapillaris complex in the central retina (macula). The macula is defined clinically by the area within the major temporal vascular arcades and provides our sharp, discriminating vision ( Fig. 43-1 ). The incidence of this disease is age dependent, and prevalence steadily increases past age 55. A common international classification exists, but most clinicians still divide ARMD into exudative (wet) and nonexudative (dry) forms.
Figure 43-1
The clinical macula describes that area of the retina encompassed by the temporal arcade vessels.
- 2.
Who develops age-related macular degeneration?
Anyone can. The greatest statistical association with macular degeneration development is increasing age. All long-term epidemiologic studies indicate an increasing prevalence of exudative and nonexudative macular changes, as well as visual loss, with increasing age. Most reports point to a greater incidence of disease in women over men. In addition, skin pigmentation plays an important role in exudative disease; African Americans have a significantly smaller incidence of choroidal neovascularization compared with Caucasians.
- 3.
Why is age-related macular degeneration such an enormous challenge?
The number of Americans age 65 and over continues to accelerate with maturation of the baby boomers. The visual morbidity and mortality associated with ARMD potentially will affect a large number of elderly Americans socially, emotionally, and economically. The loss of reading and driving vision, the increased need for social and familial support, the cost of treatment, and the resultant emotional consequences have a significant impact on increasingly limited resources.
- 4.
Describe the etiologic factors involved in the development of age-related macular degeneration.
The exact cause of ARMD is unknown, but multifactorial. In addition to increasing age, smoking is a consistent risk predictor. Individuals with a family history of ARMD have a fivefold increased risk of developing macular degeneration themselves. Genetic predisposition is an increasingly active area of research. The discovery of a genetic link in the complement factor H (CFH) gene has exposed a single nuclear polymorphism responsible for nearly 50% of ARMD risk. This supports ARMD being an inflammatory disease. Other associated gene variations in the HTRA1/ARMS2 locus on chromosome 10, hepatic lipase C (LIPC) , and tissue inhibitor of metalloproteinase 3 (TIMP3) are found in large genome-wide studies.
Female gender, white race, smoking, poor nutrition, scleral rigidity, photic exposure, previous cataract surgery, and hypertension have been implicated as well.
- 5.
Name common visual symptoms in age-related macular degeneration patients.
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Visual blur
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Central scotomas
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Metamorphopsia
Metamorphopsia is visual distortion. Images may appear smaller (micropsia) or larger (macropsia) than they really are. Patients frequently comment that straight lines such as door jams, tile patterns, telephone poles, or other straight-edged surfaces appear curved. Special graphs, Amsler grids , test the central 20 degrees of vision and are effective home-testing devices for eyes at higher risk for development of exudative ARMD. Recent results from hyperacuity home monitoring devices have shown increased sensitivity in early exudative macular disease detection.
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- 6.
What is dry or nonexudative age-related macular degeneration?
Nonexudative ARMD is characterized by drusen, pigmentary changes, and atrophy. Drusen are the most common and earliest dry ARMD changes ( Fig. 43-2 ). Drusen represent metabolic byproducts of retinal pigment epithelial cell metabolism. They vary in shape, size, and color. Hard drusen are small, discrete, yellow-to-white nodules, whereas soft drusen tend to be larger and more amorphous. Soft drusen may coalesce with neighboring drusen and are frequently associated with overlying pigmentary changes either from photoreceptor dysfunction or from retinal pigment epithelial demise. Progressive retinal pigment epithelial disruption eventually causes loss of overlying sensory retina and underlying choriocapillaris. Such developments result in localized atrophic regions that extend and coalesce around the fovea, eventually involving the fovea itself.
Figure 43-2
Drusen are the by-product of retinal metabolism and manifest as focal yellow-white deposits deep to the retinal pigment epithelium. They serve as markers of nonexudative age-related macular degeneration.
- 7.
What is wet or exudative age-related macular degeneration?
Exudative ARMD is characterized by the development of neovascular changes and fluid in and under the sensory retina and retinal pigment epithelium (RPE). Choroidal neovascular membranes progressing to end-stage disciform macular scarring are the typical outcome of untreated exudative ARMD. Variations in age-related neovascular disease include type 1 (occult), type 2 (classic), and type 3 (retinal angiomatous proliferation). All can be associated with pigment epithelial detachments. Clinically, choroidal neovascular membranes are slate green-hued subretinal lesions associated with hard exudates, hemorrhage, or fluid. These vessels commonly originate from the normal choriocapillaris and enter the subretinal space through defects in the Bruch’s membrane, a collagenous layer separating the choroidal circulation from the retina ( Fig. 43-3 ). Pigment epithelial detachments are dome-shaped clear, turbid, or blood-filled elevations of the retinal pigment epithelium; they may or may not be associated with choroidal neovascular ingrowth.
Figure 43-3
Choroidal neovascular membranes gain access to the subretinal space via defects in the Bruch’s membrane (arrow). Once there, these vessels may cause bleeding and disciform scar formation, resulting in overlying retinal dysfunction.
- 1.
Nonexudative changes
- a.
Drusen
- b.
Pigmentary alterations
- c.
Atrophy: Incipient, geographic
- a.
- 2.
Exudative changes
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Hemorrhage
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Hard exudate
- c.
Subretinal, sub-RPE, and intraretinal fluid
- a.
- 8.
Name the three processes necessary for choroidal neovascular membrane development.
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Increased vascular permeability
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Extracellular matrix breakdown
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Endothelial budding and vascular proliferation
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- 9.
Describe the difference between occult and classic choroidal neovascularization.
Classic choroidal neovascularization is clinically well defined. Fluorescein angiography demonstrates a discrete hyperfluorescent lesion with a cartwheel configuration that increases in intensity over the course of the study ( Fig. 43-4 ). Occult neovascularization usually demonstrates a poorly defined, stippled, pigmented appearance with associated retinal thickening. It is not well localized with fluorescein angiography, exhibiting diffuse punctate hyperfluorescence ( Fig. 43-5 ).
