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Age-Related Macular Degeneration

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Overview

Age-related macular degeneration (AMD) is characterised as the chronic and progressive loss of central vision in the elderly. It is due to the damage of macular retinal pigment epithelial cells. It can lead to the following changes:

  • Formation of drusen (soft exudates):
    • Deposits lying beneath the retinal pigment epithelium
    • Seen as pale-yellow spots on the retina
  • Choroidal neovascularisation:
    • Formation of new blood vessels under the retina – they can be fragile and leak
    • This leads to haemorrhage and scar formation
  • Atrophy of photoreceptors
    • Seen as a pale or washed-out-looking retina

The macula is the part of the retina we use to see directly in front of us and has a high concentration of photoreceptors. When we look directly at an object, our macula is facing it. You are reading this text using your maculae.

Epidemiology

  • Most common cause of visual impairment in older adults
  • 90% of cases are dry AMD
  • 10% of cases are wet AMD
  • More common in Caucasian people
  • More common in women

Types

Dry age-related macular degeneration

The characteristic features of dry AMD are the presence of drusen, hypo- and/or hyperpigmentation of the retinal pigment epithelium, and the lack of choroidal neovascularisation:

  • Makes up 90% of cases
  • Progression of vision loss is usually gradual
  • Presence of drusen
  • Hypo- and/or hyperpigmentation of the retinal pigment epithelium
  • Partial or complete atrophy of the retinal pigment epithelium
  • Can progress to wet AMD

Wet age-related macular degeneration

In wet AMD, choroidal neovascularisation is present:

  • Makes up 10% of all cases of AMD, but 60% of advanced cases
  • Wet AMD is considered advanced at presentation
  • Choroidal neovascularisation present
  • Scarring and haemorrhages may be seen
  • Progression of vision loss is much faster – most people have severe losses after 2 years

Risk Factors

  • Increasing age
  • Family history
  • Caucasian ethnicity
  • Smoking
  • Obesity
  • Cardiovascular disease
  • Hypertension
  • History of AMD in the other eye

Presentation

Patients with AMD tend to be older and have a painless deterioration in their central vision, usually affecting near vision. In general, dry AMD progresses much slower than wet AMD. Some other features are:

  • Distortion of central vision:
    • Patients may often see distorted lines or miss letters when reading
    • This can be tested using an Amsler Grid – patients see distorted lines
  • Sudden onset or worsening of blurred/distorted central vision:
    • This suggests choroidal neovascularisation and leakage of fluid
  • Photopsia:
    • Seeing flickering/flashing lights
  • Light glare
  • Fundoscopy signs:
    • Drusen – suggests dry AMD
    • Macular hypo-/hyperpigmentation – suggests dry AMD
    • Geographic atrophy – suggests late dry AMD
    • Choroidal neovascularisation – suggests wet AMD
    • Well-demarcated red areas – suggest leakage or haemorrhage

It is important to note that some patients may not notice vision problems when one eye is affected. They typically start to notice problems when the second eye becomes affected.

Differential Diagnoses

Cataracts

  • Faded colour vision may be present
  • Halos around light may be present
  • Defects in red reflex present

Central retinal vein occlusion

  • Onset is sudden
  • Severe retinal haemorrhages seen

Central retinal artery occlusion

  • Onset is sudden
  • Pale retina with “cherry red” spot seen

Investigations

If AMD is suspected, urgently refer the patient to an ophthalmologist.

  • Fundoscopy:
    • May show drusen, macular hypo-/hyperpigmentation/geographic atrophy/choroidal neovascularisation/well-demarcated red areas
  • Amsler grid assessment
    • Patients experience distortion of lines
  • Slit-lamp examination
    • May show drusen, macular hypo-/hyperpigmentation/geographic atrophy/choroidal neovascularisation/well-demarcated red areas
  • Optical coherence tomography – if choroidal neovascularisation suspected
    • To confirm the presence of subretinal or intraretinal fluid
  • Fluorescein angiography – if choroidal neovascularisation suspected
    • Fluorescein dye injected intravenously and retinal photographs are taken which can show neovascularisation and leakage
    • Definitive test to confirm neovascularisation and leakage

Diagnosis

Diagnosis is based on clinical features and investigations. NICE has a classification system based on severity. See their guidelines for more detail. The categories are:

  • Normal eyes
  • Early AMD:
    • Early AMD with a low risk of progression
    • Early AMD with a medium risk of progression
    • Early AMD with a high risk of progression
  • Late AMD (indeterminate)
  • Late AMD (wet active)

Management

Dry AMD

There is no specific treatment for dry AMD. Management involves modifying risk factors, active observation, and offering the AREDS2 high-dose vitamin supplements.

Wet AMD

  • 1st-line: intravitreous injection of vascular endothelial growth factor (VEGF) inhibitors:
    • VEGF stimulates neovascularisation, therefore inhibiting it can prevent the progression of wet AMD
    • Options are: ranibizumab, aflibercept, brolucizumab, or bevacizumab
  • 2nd-line: thermal laser photocoagulation
    • This is aimed at destroying choroidal neovascularisation
    • Only given in special circumstances due to the risk of visual loss after treatment

Monitoring

Dry AMD

  • NICE recommend that patients who have been discharged from hospital eye care should self-monitor their AMD and seek immediate help if their vision changes. Some symptoms may be:
    • Blurred/grey patches in their vision
    • Straight lines looking distorted
    • Objects looking smaller than normal
  • NICE also recommends that patients should continue attending routine eye tests with their community optometrist

Wet AMD

  • Patients are followed up regularly with a specialist with regular optical coherence tomography performed on both eyes

Patient Advice

  • Patients should seek help immediately if they have any new visual changes
  • Those with dry AMD should self-monitor for progression. They may be given an Amsler grid to help with this.

Complications

  • Development of AMD in the second eye
  • Retinal artery/vein occlusion
  • Vision loss and its associated complications:
  • Retinal detachment – in wet AMD
  • Haemorrhage – in wet AMD

Prognosis

  • Central visual loss is common but a total visual loss is very rare in AMD
  • Untreated wet AMD can lead to significant visual loss within 3 years
  • Untreated wet AMD carries a poor prognosis, however, the prognosis is significantly improved with early treatment

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