Photodynamic therapy (PDT) is a treatment for wet age-related macular degeneration (wet AMD). It is not used to treat dry AMD.
In photodynamic therapy, a light-sensitive medicine called verteporfin (Visudyne) is injected into the bloodstream. The medicine collects in the abnormal blood vessels under the macula. Laser light is then shone into the eye, which activates the medicine and causes it to create blood clots that block the abnormal blood vessels.
By sealing the leaky blood vessels, photodynamic therapy slows down:
- The buildup of fluid under the retina that distorts the shape and position of the macula.
- The growth of scar tissue and the abnormal membrane under the retina, both of which damage the cells in the macula.
- Central vision loss.
Photodynamic therapy takes about 20 minutes and may be done in a doctor's office or eye clinic.
What To Expect After Treatment
The verteporfin medicine used in PDT makes your skin and eyes more sensitive to light. After treatment, avoid direct sunlight for 2 to 5 days. And when you have to be outdoors, wear dark sunglasses to protect your eyes.
Your doctor will want you to come back for a follow-up exam in about a month.
Why It Is Done
By limiting the growth of abnormal blood vessels under the macula, photodynamic therapy may help prevent the progression of wet AMD. It does not restore vision to eyes that have already been damaged. But it may help prevent further damage to the retina and further vision loss.
Some experts think that photodynamic therapy may be more effective and less destructive than laser surgery. Laser treatment almost always causes some immediate, permanent central vision loss (a central blind spot). And laser treatment does not always prevent future growth of abnormal blood vessels. Photodynamic therapy may be better able to target the blood vessels without damaging the nerve cells in the retina and macula.
How Well It Works
PDT can lower the risk of severe vision loss by reducing the growth of and leakage from abnormal blood vessels under the retina.2 How well the treatment works depends on where and how the abnormal blood vessels are growing beneath the retina. For some types of wet AMD, the treatment has no detectable benefit.
The effect of PDT in slowing the progress of AMD is often temporary, and the abnormal blood vessels begin leaking again after about 3 months. Most people need multiple treatments to get the full benefits of the therapy.
A severe loss in visual clarity happens to some people who are treated with PDT. In some cases, vision partially recovers.
Other side effects that may occur with PDT include:
- Temporary visual disturbances (abnormal vision, decreased vision, defects in the visual field).
- Pain, swelling, bleeding, or inflammation at the site where the verteporfin medicine is injected. Some people also experience low back pain related to the injection of the medicine.
- Photosensitivity reactions (such as sunburn).
What To Think About
Photodynamic therapy (PDT) has been shown to be effective for only certain types of wet AMD.
The effectiveness and long-term consequences of PDT are still being studied.
Rosenfeld PJ, et al. (2009). Age-related macular degeneration. In M Yanoff et al., eds., Ophthalmology, 3rd ed., pp. 658-673. Edinburgh: Mosby Elsevier.
Primary Medical ReviewerKathleen Romito, MD - Family Medicine
Specialist Medical ReviewerChristopher J. Rudnisky, MD, MPH, FRCSC - Ophthalmology
Current as ofAugust 21, 2015