Age-related macula degeneration
Description
Age-related macula degeneration (AMD, ARMD) is a degeneration of the cells in the macula part of the retina. With age this area deteriorates and leads to a reduction in vision. It is the most common cause of blind registration in the UK. However only the macula is affected causing central vision to be impaired. The rest of the retina continues to function normally providing normal peripheral vision.
Macula degeneration exists in two forms, wet and dry. In the dry form there is a gradual thinning of the retina with slowly deteriorating central vision. These changes become universal with increasing age and in their earliest stages have little impact on vision.
In the wet form abnormal blood vessels (neovascular membranes) grow into the retina. These vessels are leaky and give rise to fluid and blood within the retina with an often rapid deterioration in vision. These changes are usually superimposed on pre-existing dry changes.
Risk factors for developing AMD include:
Increasing age
Smoking
Female
Caucasian race
Family history of AMD
Hypertension
Clinical Features
Loss of central vision affecting eg. reading, recognition of faces, detail, or a blank patch in the vision. The course is slowly progressive in the dry form, frequently rapid if wet AMD develops.
Distortion
Retinal examination will show pale deposits (drusen), pigmentary and atrophic changes in the dry form; additional fluid, retinal elevation, exudate and often blood is seen when neovascular membranes form.
Management
Dry AMD:
No treatment has been shown to restore vision that has been lost. Altering glasses is usually ineffective. Magnifiers may increase use of remaining vision and patients may benefit from an appointment in a low-vision aids clinic. Where loss of vision is severe registration as sight-impaired may be indicated.
To prevent deterioration it is recommended that patients stop smoking. Nutritional supplements have also been shown to reduce the chance of deterioration in patients with moderate or advanced dry AMD. These need to be of the same formula as used in the AREDS study. The value of lutein supplements is not yet established.
A sudden deterioration in sight in a patient with dry AMD may indicate the development of wet changes and requires urgent assessment by an ophthalmologist.
Wet AMD
New treatments for wet AMD are now available which may halt and in some cases reverse the loss of vision due to neovascular membrane formation. These include thermal laser treatment, cold laser photodynamic therapy (PDT), and intra-ocular injections of drugs that cause regression of neovascular membranes (eg Macugen, Lucentis) or reduction in fluid leakage (eg triamcinolone).
To be effective these treatment are best given as soon as possible after onset of symptoms and an urgent referral to an ophthalmology department offering this treatment is indicated.
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