Level 1: Likely reliable evidence
Photodynamic therapy (PDT) involves injection of photoreactive chemicals, such as verteporfin, that become activated after light irradiation and emit free radicals. These free radicals destroy blood vessels but do not cause retinal damage.
A recent systematic Cochrane review evaluated the efficacy of PDT in patients with choroidal neovascularization due to age-related macular degeneration; three randomized placebo-controlled trials with 1,022 patients were included (Cochrane Database Syst Rev. 2007:CD002030). Two of the trials were conducted by the same investigator and funded by the manufacturer of verteporfin. An average of five treatments per patient was administered over two years.
Fewer treated patients lost three or more lines of visual acuity (NNT 9 at 1 year, NNT 7 at 2 years) and six or more lines of visual acuity (NNT 12 at 1 year, NNT 7 at 2 years). Use of verteporfin was associated with higher rates of visual disturbance and infusion-related back pain. Visual disturbance was not clearly defined but did not affect any of the visual-acuity outcomes.