Age-related macular degeneration

Age-related macular degeneration is the most common cause of blindness in the UK. Degeneration of the central retina (macula) is the key feature with changes usually bilateral. ARMD is characterised by degeneration of retinal photoreceptors that results in the formation of drusen which can be seen on fundoscopy and retinal photography. It is more common with advancing age and is more common in females.

Risk factors

• advancing age itself is the greatest risk factor for ARMD
  • the risk of ARMD increases 3 fold for patients aged older than 75 years, versus those aged 65-74.
• smoking
  • current smokers are twice as likely as non-smokers to have ARMD related visual loss, and ex-smokers have a slightly increased risk of developing the condition, (OR 1.13).
• family history is also a strong risk factor for developing ARMD
  • first degree relatives of a sufferer of ARMD are thought to be four times more likely to inherit the condition.
• other risk factors for developing the condition include those associated with an increased risk of ischaemic cardiovascular disease, such as hypertension, dyslipidaemia and diabetes mellitus.

Classification

Traditionally two forms of macular degeneration are seen:

• dry macular degeneration
  • 90% of cases
  • also known as atrophic
  • characterised by drusen - yellow round spots in Bruch's membrane
• wet macular degeneration
  • 10% of cases
  • also known as exudative or neovascular macular degeneration
  • characterised by choroidal neovascularisation
  • leakage of serous fluid and blood can subsequently result in a rapid loss of vision
  • carries the worst prognosis

Recently there has been a move to a more updated classification:

• early age-related macular degeneration (non-exudative, age-related maculopathy): drusen and alterations to the retinal pigment epithelium (RPE)
• late age-related macular degeneration (neovascularisation, exudative)

Clinical features

Patients typically present with a subacute onset of visual loss with:

• a reduction in visual acuity, particularly for near field objects
  • gradual in dry ARMD
  • subacute in wet ARMD
• difficulties in dark adaptation with an overall deterioration in vision at night