Macular degeneration Flashcards
Define age-related macular degeneration.
A potentially progressive maculopathy characterised by distinct clinical stages e.g. early and intermediate AMD with drusen and macular pigmentary changes, usually associated with normal or near-normal vision; and late AMD, with a decrease or loss of central vision.
What is drusen?
Yellow deposits under the retina made up of lipids and proteins
NB: these are normal age related changes if the are small < 63 micrometers; but if medium sided +/- associated with pigmentary abnormalities then they are AMD related.
What are the two forms of ARMD?
Updated classification:
- Early ARMD (non-exudative): drusen and alterations to the retinal pigment epithelium (RPE)
- Late AMD (neovascularisation, exudative)
Old classification:
- ‘Atrophic’ or ‘dry’ ARMD = 90% of cases
- ‘Wet’ or ‘exudative’ or ‘neovascular’ ARMD - 10% of cases, worst prognosis
What is the most common cause of blindness in the UK?
Age-related macular degeneration
What is the pathophysiology of ARMD?
Degeneration of the central retina (macula)
Changes are usually bilateral
Degeneration of retinal photoreceptors that results in the formation of drusen seen on fundoscopy and retinal photography
What are the risk factors for ARMD?
- Age - biggest risk factor; x3 increase in those > 75yrs than those >65 yrs
- Smoking - x2 more likely to have vision loss than non-smokers
- FH - first degree relatives x4 more likely
- CVD risk factors e.g. HTN, dyslipidaemia, DM
What are the features of wet ARMD?
- characterised by choroidal neovascularisation
- leakage of serous fluid and blood can subsequently result in rapid loss of vision
- worst prognosis
What are the main features of dry ARMD?
characterised by drusen - yellow round spots in Bruch’s membrane
What are the clinical features of ARMD?
- Reduced visual acuity - esp close vision; gradual in dry and subacute in wet ARMD
- Low night vision - difficulties in dark adaptation; worse night vision
- Fluctuating visual disturbance
- Photopsia - perception of flickering or flashing lights and glare around objects
- Visual hallucinations - result in Charles-Bonnet syndrome
O/E:
- Amsler grid testing shows distorted line perception
- Drusen on fundoscopy
- Intra-retinal or sub-retinal fluid leakage or haemorrhage (wet ARMD)
How do you diagnose ARMD?
Slit-lamp microscopy - initial investigation, shows pigmentary, exudative or haemorrhagic changes affecting retina
Colour fundus photography - provides baseline for later comparison
Fluorescein angiography - used if neovascular ARMD is suspected, guides intervention with anti-VEGF therapy
+/- Indocyanine green angiography - visualises changes in the choroidal circulation
Ocular coherence tomography - used to visualise the retina in 3D to rebeal areas of diease not shown on microscopy alone
What is the management of ARMD?
Risk factor modification
Zinc with anti-oxidant vitamins A, C, and E - reduced progression by a third in the AREDS trial, those with drusen most benefitting
Anti-VEGF - potent mitogen which drives vascular permeability in wet ARMD and inhibiting this may limit progression if given in first 2 months of diagnosis e.g. ranibizumab, bevacizumab and pegaptanib, x4 monthly injections intravitreally
Laser photocoagulation - may stop choroidal neovascularisation but risk of acute visual loss
What are the complications of ARMD and its treatments?
- Photosensitivity after photodynamic therapy
- Rupture of Bruch’s membrane or retinal pigement epithelium
- Lung cancer - beta-carotene and smoking increases risk
- Progression to advanced AMD in other eye
- Stroke and MI
- Vasculitis and retinal vascular occlusion
Intravitreal injections:
- Inflammation
- Endophthalmitis
- Traumatic lens injury
- Retinal detachment
- Inflammation
What is the prognosis with ARMD?
Patients have a 1.3% risk over 5 years of progressing to advanced ARMD in early disease
Wet AMD has worse prognosis
