Age-related macular degeneration: What can photodynamic therapy do?

Photodynamic therapy can slow down the development of certain damage to the retina occurring with age for some people with age-related macular degeneration, but it cannot reverse existing visual impairment.

The macula is the central part of the retina, and it is responsible for seeing fine details in bright light. This is because there are so many light-sensitive cells very close together in this area of the eye. As we age, some of these cells die and leave scarring. If this loss of cells goes too far, our vision will be noticeably impaired. This condition is called age-related macular degeneration (AMD) and it is the most common cause of vision loss in people over 65.

There are two forms of AMD. About 8 out of 10 people have so-called dry AMD and the others (about 2 out of 10) have wet AMD. With wet AMD, new blood vessels develop around the macula, and these can increase scarring. This kind of AMD is also called neovascular AMD. You can read more about AMD here.

There is as yet no effective treatment for dry AMD. Medicines injected into the eyes are a treatment option, though, for some people who have wet AMD. This is the most effective treatment at the moment. You can read more about these medicines and other treatments here.

In combination with other therapies, so-called photodynamic therapy is also used. This treatment is done every 3 or 4 months. It involves an injection of a light-sensitive medicine called verteporfin, which spreads through the body's blood circulation system. A laser is used to send a microscopic beam of light through the eye's lens. When the light from the laser reaches the medicine in the blood vessels, it reacts to destroy the unwanted blood vessels. The dose needs to be at a level that ensures the retina itself is not damaged.

In order to weigh the pros and cons of this treatment, researchers from the Cochrane Collaboration searched and systematically analyzed all trials of photodynamic therapy. They found 2 trials involving almost 1,000 people with neovascular (wet) AMD. Both the trials were sponsored by the product's manufacturer.

According to these trials, photodynamic therapy cannot completely stop, but can slow down the progress of vision loss for some people. From the trials it was possible to calculate that after two years, without treatment, 64 out of every 100 people with wet AMD had a noticeable loss of vision. But for people who had 5 sessions of photodynamic therapy over those 2 years, sight was worse in 50. In other words: about 14 out of every 100 people (14%) benefited from the treatment.

The trials also provide some information about adverse effects. For about 2 out of every 100 people in the trials, verteporfin treatment caused new sight problems (2%). About 2 out of every 100 people complained of temporary backache (2%). Important: because sunlight can also activate the medicine in the skin, people need to avoid direct sunlight for several days after treatment. Some trial participants experienced sunburn.

The trials also show that this therapy cannot reverse vision loss that has already happened. According to the researchers, this means that photodynamic therapy is more suitable for early AMD, when there has not been a lot of damage to vision. In Germany, the costs of photodynamic therapy for people who have wet AMD are covered by health insurance.

© IQWiG (Institute for Quality and Efficiency in Health Care)