Age-Related Macular Degeneration (AMD)

Question 1

Anatomy of Macula (4).

Answer 1

4 Key Layers :-
TOP : Photoreceptors.
2nd LAYER : Retinal Pigment Epithelium (RPE).
3rd LAYER : Bruch’s Membrane.
BOTTOM : Choroid Layer (contains blood vessels that provide blood supply to the macula).

Question 2

Differential Diagnoses of Gradual Loss of Vision (4).

Answer 2

1. Cataracts.
2. AMD (Dry - Years/Decades; Wet - Months).
3. Chronic Glaucoma (Open-Angle Glaucoma).
4. Diabetic Maculopathy.

Question 3

Epidemiology of AMD (3).

Answer 3

1. Commonest cause of blindness in the UK.
2. Commoner in the elderly and females.
3. 90% - Dry; 10% - Wet.

Question 4

Clinical Features of AMD (7).

Answer 4

1. Gradual Worsening and Central Visual Field Loss.
2. Reduced Visual Acuity (especially with Near-Field Objects).
3. Crooked/Wavy Appearance to Straight Lines.
4. Difficulties in Dark Adaptation with Overall Deterioration in Vision at Night.
5. Fluctuations in Visual Disturbances vary from day-to-day.
6. Photopsia (Flickering/Flashing Lights).
   7*. Wet AMD - acutely with a loss of vision over days that progresses over 2-3 years to cause full loss of vision and bilateral disease.

Question 5

Risk Factors of AMD (5).

Answer 5

1. Age (Greatest Risk Factor).
2. Smoking.
3. White/Chinese Ethnicity.
4. Family History.
5. Cardiovascular Disease.

Question 6

Types of AMD (2).

Answer 6

1. Dry (Atrophic) AMD - characterised by Drusen (yellow round spots) in Bruch’s Membrane.
2. Wet (Exudative/Neovascular) AMD (worse prognosis).

Question 7

Investigations of AMD (4).

Answer 7

1. Suspected Cases - Refer to Ophthalmology for Assessment and Management.
2. Initial Investigation of Choice : Slit-Lamp Biomicroscopic Fundus Examination (Findings : Pigmentary, Exudative, Haemorrhagic Changes that affect the Retina). DRUSEN is the characteristic finding. Drusen can become confluent in later disease to form a macular scar.
3. OCT (Optical Coherence Tomography) - cross-sectional view of the layers of the retina - used 1st line to diagnose wet AMD.
4. Fluorescein Angiography (inject contrast and photograph retina to analyse blood supply) - 2nd line in diagnosing wet AMD.

Question 8

Management of Dry AMD (3).

Answer 8

1. No specific treatment.
2. Aim : Slow progression.
3. Lifestyle measures e.g. avoid smoking, controlling BP, vitamin supplementation.

Question 9

Management of Wet AMD (2).

Answer 9

1. Anti-VEGF medications e.g. Ranibizumab, Bevacizumab, Pegaptanib - injected directly into vitreous chamber once a month to slow/reverse progression of disease. This should be started within 3 months of onset.
2. Laser Photocoagulation - slows progression of neovascularisation but carries a risk of acute visual loss - not preferred.

Question 10

Pathophysiology of AMD (4).

Answer 10

1. Drusen (Yellow Deposits of Proteins and Lipids) appear between Layer 2 (RPE) and Layer 3 (Bruch’s Membrane).
2. Normal (Smaller than 63 um and Hard).
3. Features : Larger and Greater Numbers of Drusen, Atrophy of RPE, Degeneration of Photoreceptors.
4. Wet AMD - development of new vessels (neovascularisation) from Choroid stimulated by VEGF.