Age-related macular degeneration (AMD) is the commonest cause of blindness in the Western world in people over 50. It is caused by damage to the macula, the central part of the retina.
The macula is responsible for central vision, which we use for driving, reading and recognising faces. There are two forms of AMD: wet (exudative) and dry (atrophic). In the wet form, abnormal blood vessels grow at the back of the eye. These can bleed and cause swelling, which may reduce vision. Without treatment, that loss of sight is usually rapid and severe.
It is the commonest cause of blindness in the Western world in people over 50.
Other conditions can also cause abnormal vessels to grow at the back of the eye, among them myopia, presumed ocular histoplasmosis syndrome and angioid streaks. In every case, without effective treatment there is a high risk of severe and permanent loss of vision.
Treatments
Research has produced several therapeutic options in recent years, such as photodynamic therapy and pegaptanib (Macugen®). The latter involves injecting a drug into the eye that can halt the growth of these abnormal vessels. Although both treatments have proved effective, most patients do not experience an improvement in vision.
More recently a new molecule called bevacizumab (Avastin®) has been developed. It can stop vision from deteriorating and, in some cases, even improve it.
Some patients see an improvement in vision after treatment.
This drug was not designed specifically for the eye. On the basis of clinical trials demonstrating its safety and efficacy, Avastin® is approved by the US Food and Drug Administration (FDA) for the treatment of colorectal cancer. In ophthalmology it works by blocking a substance known as vascular endothelial growth factor (VEGF), which in turn prevents abnormal blood vessels from growing.
Avastin® is currently used in ophthalmology to treat AMD, which is an off-label use. Clinical experience shows favourable effects at the retina. The aim of treatment is to prevent progressive loss of vision. Although some patients improve, sight already lost during the process is not restored.
How is it given?
It is given as an intravitreal injection, after topical anaesthetic drops. To ensure the highest standards of sterility the treatment is carried out in the operating theatre. It is a day-case procedure, so patients can go home once it is finished.
Avastin® is injected at regular intervals (every four to six weeks). The ophthalmologist will decide how many doses are needed depending on how the condition progresses.
Other drugs with very similar properties, this time licensed specifically for ophthalmic use, are expected shortly.