Macular Degeneration, Age-Related

Description

• Age-related macular degeneration (ARMD) is the leading cause of irreversible, severe visual loss in persons age >65 years.
• ARMD results in pigmentary changes in the macula or typical drusen associated with visual loss to the 20/30 level or worse, not caused by cataract or other eye disease, in individuals >50 years of age, although some definitions exclude age or visual acuity criteria.
• Stages
  • Atrophic/nonexudative
  • Neovascular/exudative
• System(s) affected: nervous
• Synonym(s): senile macular degeneration; subretinal neovascularization (SRN)

Epidemiology

• Neovascular/exudative form is rare in blacks and more common in whites.
• Predominant sex: female

• In the Framingham Eye Study (FES), drusen were noted in 25% of all participants who were ≥52 years of age. ARMD-associated visual loss was noted in 5.7%.
• Atrophic/nonexudative stage accounts for 20% of cases of severe visual loss.
• Neovascular/exudative stage accounts for 80% of cases of severe visual loss.

Per FES study:

• People 65 to 74 years old: 11%
• People ≥75 years old: 27.9%

Etiology and Pathophysiology

• Breaks in the Bruch membrane allow choroidal neovascular membranes (CNVMs) to invade the retinal pigment epithelium (RPE) and grow into the subretinal space.
• Atrophic/nonexudative: drusen and/or pigmentary changes in the macula
• Neovascular/exudative: growth of blood vessels underneath the retina
• Visible light can result in the formation and accumulation of metabolic by-products in the RPE, a pigment layer underneath the retina that normally helps remove metabolic by-products from the retina. Excess accumulation of these metabolic by-products interferes with the normal metabolic activity of the RPE and can lead to the formation of drusen.
• Neovascular stage generally arises from the atrophic stage.
• Most do not progress beyond the atrophic/nonexudative stage; however, those who do are at a greater risk of severe visual loss.

• Genetic susceptibility may be a factor in ARMD: ~25% genetically determined
• Complement factor H is an important susceptibility gene for ARMD.
• Although the development of ARMD may be predicted by specific alleles, the clinical response to antivascular endothelial growth factor (VEGF) is not.

Risk Factors

• Obesity
• Ethnicity: non-Hispanic whites
• Cigarette smoking
• Chlamydia pneumoniae infection
• Family history
• Excess sunlight exposure
• Blue or light iris color
• Hyperopia
• History of cardiovascular disease
• Short stature
• Aspirin use
• Female sex

General Prevention

• Ultraviolet (UV) protection for eyes
• Routine ophthalmologic visits
  • Every 2 to 4 years for patients age 40 to 64 years
  • Every 1 to 2 years after age 65 years
• Patients who take statins, which modify lipid profiles, may have a reduced risk.

Commonly Associated Conditions

• Presumed ocular histoplasmosis syndrome
• Exudative retinal detachment
• Vitreous hemorrhage
• Other causes of CNVMs