Age-related macular degeneration (AMD)

Essentials

  • Age-related macular degeneration (AMD or ARMD ) refers to the degeneration of the area of high-acuity vision (macula) in the fundus of the eye, associated with aging.
  • The non-exudative or dry form progresses slowly, the exudative or wet form rapidly (within days or weeks).
  • Refer a patient with suspected exudative form of the disease without delay for investigations and treatment. Also consider the significance of the disease in the patients' daily life.
  • An elderly patient may think that reduced visual acuity is a result of cataract or secondary cataract or of out-of-date spectacles, in which case the exudative AMD progresses to an advanced state and visual acuity is markedly reduced before the patient receives treatment.

Epidemiology

  • The most common cause of visual impairment in patients aged over 65 years in industrialized countries
  • Some degree of AMD is seen in 10% and severe form in 1% of persons older than 60 years. It is bilateral in two out of three patients.
  • About 10–20% have the exudative form of AMD, and 80–90% have the "dry" non-exudative form.

Pathogenesis

  • Age is the most important risk factor: the pigment epithelium and photoreceptor cells grow old causing the degeneration of the retinal area of central vision.
  • Smoking is an important risk factor.
  • Changes in the circulation of the fundus (arteriolosclerosis) may also contribute.
  • AMD seems to have certain risk factors in common with general cardiovascular morbidity: hypertension, hypercholesterolaemia, overweight, low level of physical activity, and a diet that contains insufficient amounts of protective nutrients (antioxidants).
    • Use of fish and vegetables in the diet decreases the risk of AMD.
  • Persons with AMD have been shown to have genetic predisposition to it; e.g. polymorphism in genes associated with complement factor H and ARMS2 increase the risk.

Types

Non-exudative or dry form

  • Pigment epithelium and photoreceptor cells degenerate and die (a type of degenerative change).
  • In the early phase of the non-exudative form, because of the uneven distribution of pigment in the pigment epithelium, pigment clumps and depigmented areas are seen in the fundus as well as yellowish, rather regular round pale waste product deposits often of varying size (drusens). In the more advanced phase of the non-exudative form, there are large atrophic areas lacking photoreceptor cells and pigment epithelium.
  • The degeneration progresses slowly over years and decades.

Exudative or wet form

  • May develop from the dry form.
  • New vessels grow from the choroid through breaks in Bruch's membrane under the retinal pigment epithelium and the retina. These vessels are fragile and easily bleeding.
  • In addition to the changes seen in the dry form, oedema, yellowish lipid deposits and bleeding are seen.
  • The bleeding may sometimes spread to the vitrous space.
  • The condition usually progresses rapidly over days and weeks.
  • Differential diagnosis: macular oedema of different causes, among others diabetic maculopathy (see also article (Impaired vision), under metamorphopsia).

Symptoms

  • Elderly patients most often notice the symptoms only when the second, better eye is affected (when the non-dominant eye was first affected). The first eye may have already lost vision without being noticed.
  • Typical symptoms include distortion of straight lines (metamorphopsia) and changes in picture size (micropsia, macropsia); e.g. during reading the size of the letters may change and some letters may disappear.
  • The patient may see a grey central patch or a part of the central vision may be lacking (relative or absolute scotoma) which makes it difficult to read or recognise people's faces.
  • The patient may experience that her/his colour vision has changed (especially blue and yellow colours).
  • Both near and distance vision progressively deteriorate (eventually typically 0.3 to 0.1 in the non-exudative form and count finger in the exudative form).

Diagnosis

  • Based on fundus findings.
  • Refer the patient to an ophthalmologist for confirmation of the diagnosis. Patients with exudative AMD need a rapid referral for possible treatment with a vascular endothelial growth factor (VEGF) inhibitor or with photodynamic therapy.

Treatment

  • Intravitreously administered inhibitors of vascular endothelial growth factor (VEGF; ranibizumab, bevacizumab and aflibercept) have been shown to halt the deterioration of vision and even improve the prognosis of vision [Evidence Level: A]. Photodynamic therapy [Evidence Level: A] is also used for the treatment of some types of AMD. The treatment possibilities are always assessed by an ophthalmologist.
  • The patient will not be completely blinded.
    • Reading vision may be destroyed.
    • Peripheral visual fields are preserved and thus also the vision required for moving around so that the daily activities at home may be performed moderately well.
    • Communication becomes more difficult because the patient cannot see facial expressions. Many elderly patients also have impaired hearing which aggravates the communication problems.
  • In rehabilitation it is essential
    • to take care of the provision of assistive devices and to instruct in the use of geometric magnification (e.g. the television is watched from a shorter distance)
    • to ensure sufficient levels of lighting in the home and to guarantee the safety of the kitchen to prevent burn injuries (e.g. protective gloves for handling of hot dishes)
    • to arrange for the management of the home, shopping and errands.
  • In a considerable number (about 30%) of people with the exudative form of AMD, even the other eye will be affected within five years, and the disease may progress in the already treated eye.
  • Regular examination of the vision using Amsler grid chart https://www.aao.org/eye-health/tips-prevention/facts-about-amsler-grid-dai... is important in the follow-up. If the patient registers new changes in the grid (distortions of lines or scotomas), he/she should seek treatment.
  • Certain forms of the non-exudative type are associated with a higher risk of developing to the exudative form of AMD, and the ophthalmologist may suggest medication to reduce the progression speed of non-exudative AMD. The medication consists of high doses of antioxidant and trace element supplements (vitamins C and E, beta carotene [beta carotene not for smokers] and zinc as trace element) [Evidence Level: B].

Evidence Summaries

References

1. Schmidt-Erfurth U, Kaiser PK, Korobelnik JF et al. Intravitreal aflibercept injection for neovascular age-related macular degeneration: ninety-six-week results of the VIEW studies. Ophthalmology 2014;121(1):193-201.  [PMID:24084500]

2. Comparison of Age-related Macular Degeneration Treatments Trials (CATT) Research Group., Martin DF, Maguire MG et al. Ranibizumab and bevacizumab for treatment of neovascular age-related macular degeneration: two-year results. Ophthalmology 2012;119(7):1388-98.  [PMID:22555112]


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