Introduction Wet macular degeneration occurs on a background of dry macular degeneration. It is caused by new blood vessels growing under the retina, which may leak fluid causing the retina to become thick and not work as well or causing bleeding which directly stops the light being focussed onto the retina. Bleeding may heal with scarring which obviously disrupts retinal function reducing vision. The aim of treatment is to convert wet macular degeneration to the dry type.
Treatment We only have treatment for the wet forms of the disease and these have only become available since 2001 with the advent of first photodynamic therapy (PDT), then Macugen (2006) and now Lucentis/Avastin (2007). The most promising results to date have been achieved with Lucentis (strictly called ranibizumab). This is a specially devised molecule that inactivates the chemical messenger VEGF (vascular endothelial growth factor) that causes new blood vessel growth. Avastin (bevacizumab) and Lucentis are very similar molecules at the business end that binds VEGF. They differ mainly in their size. Avastin was designed to be given in the blood to treat bowel cancer. The molecule was thought to be too large to penetrate the retina, so Lucentis was developed as a spin-off. However, many ophthalmologists have found that avastin, like Lucentis, is very effective in treating AMD. I only use Avastin or Lucentis now, as these drugs work. 95% of patients will lose no more than 3 lines of vision after one year with these injections compared to only 50% of patients not receiving these injections. And some 40% of patients will have an improvement of 3 or more lines of vision with these injections.
How the treatment is given The eye is first numbed with drops and the surface cleaned with iodine. A speculum is placed to keep the lids apart and a tiny injection given 3 to 4 mm behind the junction of the iris with the white of the eye. Patients will often feel a pressure and discomfort as the injection is given. It is little different from having your blood taken (sometimes it hurts more than others depending on whether a nerve is touched by the needle). Immediately afterwards, patients might see one or two bubbles in their vision and often the eye is sore for 2 days because of all drops used to numb and clean the eye.
Number of injections Patients need to be given a series of monthly injections. The precise number will vary from patient to patient. A course of 3 injections is the minimum required, although most have to have 6 injections before monthly monitoring and repeat injections as necessary. The latest evidence suggests that more frequent injections may be required. Certainly some patients need long-term monthly injections to prevent relapse.
Complications of treatment
Eye complications The main complication is infection which occurs in 1:10000 injections. Great precautions are taken to try and prevent this. Very rarely, a retinal detachment or damage to your crystalline lens can occur. The injection can rarely damage the crystalline lens, complicating subsequent cataract surgery.
Other complications When Avastin has been injected into the blood in ill patients with bowel cancer, 3-4% of patients developed strokes and heart attacks. Some patients have had problems with wounds breaking down. Although, much lower doses are used to treat AMD when injected directly into the eye, these risks should be considered when Avastin is used for AMD. We are more likely to use Lucentis for AMD treatment, howver, and the risk of these complications is thought to be lower with this drug.
Where the treatment is given These treatments are given at the Somerfield Hospital.
Other treatments Surgery is very much a last resort. Macular translocation surgery may be of benefit in patients with a short history of massive bleeding in one eye when the other eye has already been badly affected by AMD. The surgery is very complex and, when it goes well, is only likely to partially improve vision. Some surgeons are offering intraocular telescopes to focus light onto functioning parts of the retina. This procedure is currently very experimental.
Prevention Some people can have changes in the back of their eyes which predispose them to getting AMD. In some of these patients, the 5 year risk of advanced AMD can be of the order of 25% to 40%. One important study showed that taking a dietary supplement of vitamins A, C, E with Zinc decreased the 5 year risk of advanced AMD from 28% to 20% ( a 25% risk reduction). Current studies are looking at whether the addition of lutein, zeaxanthin and/or fish oils give any additional benefit. There is some evidence that statins may reduce the risk of AMD.