Age-related macular degeneration (AMD)
The macula is the central part of the retina that is involved in central sharp vision. Age-related macular degeneration (AMD) is one of the leading causes of irreversible visual loss in individuals over the age of 60.
AMD can be broadly classified as:
Non-exudative or Dry AMD
This is the more common form, accounting for 90% of AMD cases. There is a slow progressive deterioration of the nerve function.
Exudative or Wet AMD
This makes up 10% of cases of AMD and may cause devastating visual loss. In some instances, good vision may be lost within a few days. It results from the development of abnormal leaky vessels or a membrane beneath the retinal layer. These abnormal vessels may bleed or leak fluid, proteins or fats. This can give rise to a separation of the retinal layers and loss of vision. In the late stage this may lead to scarring over the macula.
In dry ARMD, the patient may experience a gradual progressive loss of central vision. Patients may not realize they have this until the disease is more advanced and the central vision becomes blurry or distorted.
In wet ARMD, there may be a sudden dramatic loss of vision. There may also be distortion of vision or a shadow over the central vision. The visual loss may be profound.
Diagnosis and Treatment
An eye specialist will be able to confirm the presence of ARMD. Fundus fluorescein angiogram may be performed to look at the extent and severity of the disease.
For dry ARMD, certain lifestyle modifications such as stopping smoking may help reduce progression of the disease. The use of low vision aids may also help in the visual rehabilitation of patients.
For wet ARMD, a new and improved treatments involves injecting special medication into the eye to stop abnormal blood vessel growth and leakage. These drugs (e.g. Lucentis (ranibizumab) and Avastin (bevacizumab)) work by inhibiting proteins called vascular endothelial growth factor (VEGF), which stimulate the growth of new blood vessels in the body. VEGF is thought to contribute to development of macular degeneration by promoting the growth of abnormal blood vessels in the retina. Clinical trials have shown that these new treatments gave patients better visual results compared to traditional treatment using lasers alone.
These may be combined with laser treatment to seal off the abnormal vessels. Argon laser or photodynamic therapy with Visudyne treatment may also be used, depending on the nature and location of the abnormal vessels and membrane. These treatments may help to slow down the progression of the disease and prevent further visual loss.