Age Related Macular Degeneration
Just the Basics

Age-related macular degeneration is a chronic progressive degenerative disorder of the macula, causing progressive deterioration in vision; it’s the leading cause of blindness in the UK.

ARMD can be categorised into two main types: dry-ARMD i.e. atrophic, which accounts for 90% of cases and is characterised by drusen, and wet ARMD i.e. exudative, which accounts for 10% of cases, is characterised by choroidal neovascularisation and carries a worse prognosis.

Anatomy and physiology

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The macular is a small oval-shaped pigmented area situated in the centre of the retina, at the back of the eye, which is responsible for our central vision. It consists of four layers, from deep to superficial: choroid (vascularised) layer, Buch’s membrane, retinal pigment epithelial layer, photoreceptor layer (rods and cones).

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Schematic of layers of the macula

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Dry

ARMD is characterised by the presence of drusen, which are yellow lipid deposits that appear between the Bruch’s membrane and retinal pigment epithelial layer. Larger and greater clusters of drusen are indicative of macular degeneration.

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Drusen – present in intermediate dry-ARMD

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Wet

ARMD oversees the expression and secretion of a pro-inflammatory cytokine vascular endothelial growth factor (VEGF), which ultimately leads to neovascularisation (new blood vessel growth) and increased vascular permeability. This occurs from the choroid layer into the retina. The newly growing retinal vessels subsequently leak serous fluid and blood, causing oedema which damages the photoreceptor layer, leading to rapid vision loss. 

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Wet-ARMD with choroid neovascularisation, sub-retinal haemorrhage and geographic atrophy

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Diagnosis

Patients with ARMD may present with:

• Decreased visual acuity – progressive i.e. over 2-3 years (dry) or sudden-onset i.e. within days (wet)

• Scotoma

• Worsening central visual field loss

• Blurred vision (crooked/wavy appearance of straight lines)

• Distorted near vision 

• Photopsia, (a perception of flickering or flashing lights)

• Glare around objects

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Risk Factors to check include:

• Advanced age

• Smoking history

• Family history

• Cardiovascular risk factors: hypertension, dyslipidaemia

• Diabetes mellitus history

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Examination Findings:

Dry - Drusen, pigmentary changes, geographic atrophy

Wet - Choroid neovascularisation, intra-retinal or sub-retinal fluid, pigment epithelial detachments (PEDs), sub-retinal haemorrhage

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A comparison of fundoscopic changes seen in dry vs wet ARMD, with corresponding OCT depiction of these changes

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Further investigation to help aid diagnosis

• Slit lamp microscopy (identify any pigmentary, exudative or haemorrhagic changes),

• Colour fundus photography (provides baseline against which changes can be identified over time)< >

• Optical coherence tomography (OCT) – used to visualise the retina in 3 dimensions and helps evaluate for neovascular membrane formation

• Fundus fluoroscein angiography (FFA) – if neovascular ARMD is suspected, as this can guide intervention with anti-VEGF therapy - and indocyanin green (ICG) as this can visualise any changes in the choroidal circulation

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Fundus fluoroscein angiogram of choroid neovascularisation in wet-ARMD

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Treatment

Dry-ARMD is typically managed conservatively, with risk factor modifications and nutritional supplementation acting as primary treatment measures. A combination of zinc, vitamin A, vitamin E and vitamin C was shown to reduce progression of dry-ARMD in a third of patients who took part in the AREDS trial; as such, moderate category dry-ARMD is treated with these supplements, and helps to prevent progression to wet-ARMD.

Anti-VEGF and OCT are the primary treatment methods for exudative wet-ARMD. Anti-VEGF treatments such as ranibizumab and bevacizumab are administered as 4 weekly injections, and act to decrease retinal oedema and subsequently maintain vision through targeting the angiogenic properties of VEGF. Laser photocoagulation is a less preferred treatment, compared to anti-VEGF, due to the risk of acute visual loss it carries.

Follow-up is carried out by spectral-domain (SD)-OCT, which monitors treatment efficacy and response over time.