Photodynamic Therapy (PDT) is a treatment used to treat abnormal leaking blood vessels due to wet age-related macular degeneration. It is also used in conditions associated with abnormal vessel growth such as myopic (near-sighted) degeneration.
PDT involves a combination of drug and laser treatment. A light sensitive medication (photosensitizer) called verteporfine (Visudyne) is injected into the bloodstream through an arm vein. It travels through the circulation to the eye, and collects in the abnormal leaking blood vessels under the retina over nearly 15 minutes. A low energy laser is then used to activate the drug that seals the leaking blood vessels and promotes their closure. Unlike thermal laser, this low energy laser does not cause a burn and there is less sacrifice of the surrounding functional retinal tissue.
The goal of treatment is to preserve vision and delay or prevent further visual loss. Sometimes succesive PDT tretaments or combination therapies are needed.
The risks of photodynamic therapy are very low. The procedure is performed in the office and typically takes under 20 minutes. There is generally no discomfort, although a small percentage of patients report back pain during the infusion of the medication. Given the light sensitivity of the dye and its delivery into the bloodstream, patients are advised to avoid direct sunlight for at least 2 days after treatment.