About the Study
The study is called the Verteporfin Photodynamic Therapy cohort study, or VPDT cohort study for short. Anybody found to have subfoveal classic or predominantly classic choroidal neovascularization (CNV) is being offered treatment on the National Health Service (NHS).
Although photodynamic therapy (PDT) has been approved for use on the NHS, the NHS needs to record the condition of patients' eyes before the treatment is given and the results of the treatment. This is the purpose of the cohort study.
The information collected will allow the value of PDT treatment over time to be assessed.
PDT is a treatment which has only been available for use since 2002. The clinical trials which tested this treatment showed that sight loss measured by testing on vision test charts was reduced in patients who received the active treatment relative to the dummy treatment. However, many of the treated patients also continued to lose eyesight. As the treatment is given every 3 months for a number of years, is expensive and may not be of benefit in a high proportion of those treated, it is important that the results are monitored for several reasons. These include, knowing how many people actually benefit from the treatment, for how long the treatment should be continued, the best way to give it, how sight loss impacts on people's quality of life and whether PDT treatment makes a difference to this, and how much it actually costs. In the VPDT cohort study we are hoping to answer these questions.
The treatment uses a special drug called verteporfin (marketed under the name of visudyne), which sensitises the blood vessels so that they can be destroyed using a low energy laser. Visudyne is injected into the bloodstream and when there is enough visudyne in the body, a specially designed laser is focused on the retina through a contact lens placed on the eye. The whole process should cause little or no discomfort. Because the drug is mainly concentrated in the abnormal blood vessels these are preferentially destroyed and further leakage and bleeding is reduced. The surrounding normal blood vessels are also damaged but the damage is minimal and they recover very rapidly. The retina itself does not take up the drug and so does not become damaged although it is exposed to the laser. The treatment is performed by ophthalmologists who have specialised in treating retinal disorders.
The abnormal damaged vessels may recover and this is why the treatment may have to be repeated several times. Patients having PDT need to come back every 3 months to have further photos taken of the back of the eye, and whenever the abnormal blood vessels leak again, they will need another treatment. This may happen up to 4 times per year. Many patients have already been on treatment for up to 2 years. Although patients will be asked to return every 3 months initially to see their eye specialist, the frequency of these visits will be reduced if the disease stabilises. This is likely to happen around 1 year after treatment is started.
The study is being funded by the Department of Health and the regional specialised services commissioners (these are the people who provide the budget to hospitals in the UK to provide treatment to those people living in their region).
We are planning to collect information for up to 3 years.
