Epidemiology

• AMD is the leading cause of blindness in individuals > 65 years in developed countries.
  • Age of onset: usually > 55 years

Etiology

• Risk factors
  • Advanced age
  • Cardiovascular disease
  • Smoking

Pathophysiology

AMD is characterized by progressive degenerative changes in the central part of the retina (macula) → visual impairment.

• Dry AMD (∼ 90%)
  • Also referred to as nonexudative AMD or atrophic AMD
  • Deposition of yellow-whitish material consisting of lipids, vitronectin, and other proteins (drusen) in the retinal pigment epithelium and between it and Bruch membrane → slow progressive atrophy of the local retinal pigment epithelium (centrally or pericentrally)
    • The condition likely results from chronic oxidative damage to the retinal pigment epithelium and choriocapillaris, leading to subretinal inflammation with abnormal extracellular matrix formation (eg, confluent drusen, basement membrane thickening).
• Wet AMD (∼ 10%)
  • Also referred to as exudative AMD or neovascular AMD
  • Choroidal neovascularization (between the retinal pigment epithelium and Bruch's membrane) → leaking of intravascular serous fluid and blood → sudden localized elevation of the macula and/or detachment of the retinal pigment epithelium
    • Hemorrhages can cause sudden loss of vision.

Clinical features

• Painless central or pericentral visual impairment → reduced visual acuity, difficulty adapting to changes in lighting
  • Dry AMD: slow progressive visual impairment (usually over decades) and unilateral or bilateral onset
  • Wet AMD: acute or insidious onset (over weeks to months) and usually manifests in one eye first
• Metamorphopsia: type of visual distortion in which straight lines appear wavy, which can be tested for using an Amsler grid
• Scotoma (blind spot)

Diagnostics

• Amsler grid: detection of metamorphopsias and scotomas
• Fundoscopy
  • Dry AMD
    • Drusen
  • Wet AMD
    • Subretinal and intraretinal hemorrhage and/or exudate

Treatment

• Treatment of wet AMD
  • First-line: injection of VEGF inhibitors (ranibizumab, bevacizumab, pegaptanib) into the vitreous body