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Questions and Answers
What is the leading cause of irreversible blindness in people over 50 years in the developed world?
What percentage of people over 50 years are affected by age-related macular degeneration?
What is the most significant risk factor for age-related macular degeneration?
What is the role of melanin in the retinal pigment epithelium?
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What is the pathogenesis of age-related macular degeneration?
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What is the function of drusen in age-related macular degeneration?
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What is the difference between dry and wet age-related macular degeneration?
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What is the composition of drusen?
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What is the significance of large, soft drusen in age-related macular degeneration?
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What is the role of the complement factor H gene in age-related macular degeneration?
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Study Notes
Definition and Epidemiology
- Age-related macular degeneration (AMD) is a chronic degenerative disorder that affects older individuals, characterized by central visual loss.
- AMD is the leading cause of irreversible blindness in people over 50 years in developed countries.
- It affects 1 in 7 people over 50 years.
- AMD is the leading cause of legal blindness and severe vision loss in Australia.
Risk Factors
- Advanced age: risk increases from ~2% in people aged 50 years to >30% in people aged >75 years.
- Smoking: increases oxidative damage, and incidence increases with more smoking.
- Hypertension
- Obesity
- Cardiovascular disease
- Female gender
- White ethnicity
- Certain ocular conditions: blue iris color, hyperopia, and cataract
- Family history: a significant risk factor for AMD
- Genes implicated as risk factors: Complement factor H (CFH), Apolipoprotein E2 (APOE), Fibulin 5, and ABCA4
Role of RPE
- Melanin absorbs excess light to prevent UV damage
- Regenerates visual pigments
- Forms the outer blood ocular barrier
- Balances fluid and electrolytes
- Phagocytoses spent outer disc segments
- Maintains chorio-capillaries
Pathogenesis of AMD
- RPE dysfunction
- Alteration in Bruch's membrane and the extracellular matrix
- Oxidative damage
- Inflammatory processes
- Ischemia
- Drusen: a metabolic waste product between RPE and Bruch's membrane
- Sub-retinal inflammation elicited by drusen leads to further damage and ischemia
Types of AMD
- Dry (non-exudative): 90%, characterized by drusen and RPE dysfunction leading to geographic atrophy
- Wet (exudative): 10%, characterized by the formation of choroidal neovascularization (CNV) leading to retinal fibrosis and disciform scarring
Drusen
- Early signs of AMD
- Round yellow deposits located between Bruch's membrane and RPE
- Can be seen in healthy eyes due to aging (small and hard drusen)
- Classified by size: small (< 63 µm), intermediate (63 – 124 µm), and large (> 125 µm)
- Hard drusen: small, bright yellow, solid appearing drusen with well-defined margins
- Soft drusen: large, pale yellow, ill-defined, fluffy margins; high risk for neovascular AMD
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Description
Test your knowledge of age-related macular degeneration, a chronic degenerative disorder that affects older individuals and causes central visual loss. Learn about its epidemiology, symptoms, and types.
