Age-Related Macular Degeneration (AMD)
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Age-Related Macular Degeneration (AMD) is a degenerative disease of the central retina (macula). It is the leading cause of irreversible blindness in the developed world in people over 50.
It destroys central vision (reading, driving, faces) but usually spares peripheral vision (so patients do not go completely black-blind).
Classification
- Dry (Non-Neovascular) AMD: (90%). Slow, gradual atrophy.
- Wet (Neovascular) AMD: (10%). Rapid, severe vision loss due to abnormal blood vessels leaking fluid.
Clinical Scenario: The Wavy Door Frame
A 75-year-old smoker presents saying that when she looks at the bathroom door frame, the straight lines look 'wavy' or 'kinked'. She has also noticed a blurred patch in the centre of her vision when reading.
Key Teaching Points
- Visual distortion of straight lines is called **Metamorphopsia**.
- It is a classic sign of **Wet AMD** (fluid lifting the retina distorts the photoreceptors).
- It can be self-tested using an **Amsler Grid**.
- Management: Urgent Referral (<2 weeks) for OCT scan and Anti-VEGF injections.
Image Integration Plan
| Image Type | Source | Status |
|---|---|---|
| Management Algorithm | AI-generated | PENDING |
| Pathophysiology (Drusen) | AI-generated | PENDING |
| OCT Scan (Subretinal Fluid) | Web Source | PENDING |
| Amsler Grid | Web Source | PENDING |
[!NOTE] Image Generation Status: Diagrams illustrating Choroidal Neovascularisation (CNV) are queued.
Dry vs Wet
| Feature | Dry AMD | Wet AMD |
|---|---|---|
| Pathology | Atrophy of RPE. Drusen accumulation. | New vessels (CNV) grow under retina. Leak fluid/blood. |
| Onset | Gradual (Years). | Rapid (Days/Weeks). |
| Vision Loss | Mild to Moderate. | Severe. |
| Treatment | Lifestyle / Vitamins. | Anti-VEGF Injections. |
- Prevalence: Affects 5% of people > 75.
- Risk Factors:
- Age: Strongest factor.
- Smoking: Doubles the risk.
- Race: White > Black/Asian.
- Genetics: Complement Factor H (CFH) gene.
- Diet: Low antioxidants.
- Oxidative Stress: Ageing RPE (Retinal Pigment Epithelium) cells fail to clear waste products.
- Drusen: Yellow deposits of lipids/proteins (lipofuscin) accumulate between RPE and Bruch's membrane.
- Inflammation: Drusen trigger chronic inflammation and complement activation.
- Atrophy (Dry): RPE and photoreceptors die (Geographic Atrophy).
- Neovascularisation (Wet): Ischaemic retina releases VEGF (Vascular Endothelial Growth Factor). New, fragile vessels grow from the choroid, break through Bruch's membrane, and bleed/leak -> Scarring.
- Acuity: Reduced (Snellen chart).
- Amsler Grid:
- Patient looks at central dot with one eye covered.
- Do lines look straight? Are any missing?
- Fundoscopy (Dilated):
- Drusen: Yellow spots.
- Hypopigmentation: Mottling.
- Haemorrhage/Exudates: Signs of Wet AMD.
- OCT (Optical Coherence Tomography):
- Gold Standard. Like an ultrasound but uses light.
- Shows cross-section of retina.
- Wet: Subretinal fluid, retinal thickening.
- Dry: Thinning, drusen bumps.
- Fluorescein Angiography:
- Dye injected into arm. Photos of eye taken.
- Confirms leakage from new vessels.
A. Dry AMD
No cure exists. Management is supportive.
- Lifestyle: Stop smoking (vital). Healthy diet (leafy greens).
- Supplements (AREDS2 formulation):
- Vitamin C, E, Zinc, Copper, Lutein, Zeaxanthin.
- Slows progression to advanced AMD by ~25%.
- Low Vision Aids: Magnifiers, bright lights.
B. Wet AMD (Active)
Anti-VEGF Therapy (Intravitreal Injections):
- Drugs: Ranibizumab (Lucentis), Aflibercept (Eylea), Bevacizumab (Avastin - off label).
- Regimen: Injection into the eye (under local anaesthetic drops) every 4-8 weeks.
- Outcome: Stabilises vision in 90%. Improves vision in 30%.
- Duration: Often indefinite.
- Legal Blindness: Loss of driving licence.
- Falls: Due to poor vision.
- Depression.
- Charles Bonnet Syndrome: Reassure patient they are not "going mad".
- Dry: Slow decline over 5-10 years.
- Wet: unteated -> rapid central blindness (scarring) within months. Treated -> Good preservation of vision.
- NICE NG82: Age-related macular degeneration.
- AREDS2 Study: Evidence for vitamin supplementation.
What is the Macula? The retina is like the film in a camera. The Macula is the tiny bullseye in the centre of the film responsible for high-definition vision (reading, faces).
What is AMD? It is "wear and tear" of the macula.
- Dry AMD: The cells slowly wither away, like balding patches on a lawn. It is slow.
- Wet AMD: Abnormal blood vessels grow under the lawn like weeds. They leak fluid and ruin the grass quickly.
Will I go blind? You will lose your fine central vision (so reading becomes hard), but you will NOT go black-blind. You will always keep your peripheral (side) vision, so you can walk around room without bumping into furniture.
How do we treat it?
- Dry: Stop smoking and eat Kale/Spinach. No surgery works.
- Wet: We give injections into the eye to dry up the leaky vessels. It sounds scary, but it is painless (we numb the eye) and takes 5 seconds. It saves your sight.
What is the Amsler Grid? A grid of squares. Stick it on your fridge. Check it once a week with each eye. If the lines go wavy, call us immediately.
- NICE. Age-related macular degeneration [NG82]. 2018.
- AREDS2 Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration. JAMA. 2013.
- Rosenfield PJ, et al. Ranibizumab for neovascular age-related macular degeneration. N Engl J Med. 2006.