Age Related Macular Degeneration: Pathogenesis and clinical findings
Photoreceptor atrophy
-> Extracellular debris (drusen) from RPE atrophy/metabolism deposits between Bruch's membrane and RPE
-> Drusen above Bruch's membrane reduces blood flow from choroid to retina
-> Nutrients cannot reach retina from choroid and waste products from retina cannot pass into the choroidal bed
-> Ischemia of RPE and photoreceptors
-> Break occurs in Bruch's membrane
-> Blood vessels grow from the choroidal circulation into the retina
• Wet ARMD - Choroidal neovascularization seen on fundoscopy -> New abnormal blood vessels leak serous fluid and blood under the retina
- Distorted central vision -> Distortion of lines (metamorphopsia) when looking at a grid of straight lines (i .e. Amsler grid)
- Macular edema seen on fundoscopy
• Dry ARMD - Drusen depositions; geographic atrophy of RPE -> Loss of photo receptors
- Faded/blind spots in central vision -> Straight but faded lines when looking at a grid of straight lines (i.e. Amsler grid)
- Asymptomatic (early disease)
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