Age-related macular degeneration - External and Internal Eye
With age, the retinal pigment epithelium (RPE) accumulates waste products from the retina. Drusen, the hallmark of AMD, are focal deposits of this debris between the RPE and Bruch's membrane. Excess drusen can damage the RPE, leading to retinal atrophy and the expression of angiogenic cytokines. With choroidal neovascularization (CNV), choroidal vessels grow abnormally and leak or bleed into the subretinal space through defects in Bruch's membrane.
AMD can be divided into a non-neovascular (dry) atrophic type and an exudative neovascular (wet) type. The atrophic form comprises 90% of AMD and only 10% of blindness, while the exudative form makes up 10% of AMD but is responsible for 90% of vision loss.
Patients with early AMD are often asymptomatic. As the drusen cover more of the macula, patients may complain of fluctuating blurry vision or loss of contrast sensitivity. With exudative AMD, patients often note visual distortion or loss of vision.
H35.30 – Unspecified macular degeneration
267718000 – Age-Related Macular Degeneration
Differential Diagnosis & Pitfalls
- Pattern dystrophy – Seen in younger patients; lesion shows geographic shape.
- Central serous chorioretinopathy – Seen in younger individuals (usually 40-60 years of age); no drusen.
- Ocular histoplasmosis syndrome – Associated with CNV.
- Pathologic myopia – Associated with CNV.
- Choroidal ruptures – Associated with CNV.
- Angioid streaks – Associated with CNV.
- Best disease – Round or oval lesions may show different stages.
- Adult foveomacular dystrophy – Yellow / green subfoveal lesion; may simulate CNV on fluorescein angiography.
- Intraretinal lipid (hard exudates) – May look like drusen.
- Cotton wool spots – May look like drusen.
- Retinal vascular occlusion (eg, central retinal vein occlusion) – Associated with retinal hemorrhage.
- Diabetic retinopathy – Associated with retinal hemorrhage.
- Drug toxicity – Macula may appear mottled.