Question: What is photodynamic therapy, when is it used to treat age-related macular degeneration (AMD) and what are the risks/benefits?
Answer: Photodynamic therapy is a treatment that uses a drug that's introduced intravenously and then travels to the target tissue -- in this case, the macula -- and the drug is then activated by laser light. The activated drug then injures the abnormal blood vessel wall and causes them to clot. When we only had photocoagulation, it was not really selective at all, and one ended up with a scar and damaged retina whereever you treated, and it was really not very effective if you were trying to treat the abnormal blood vessels right in the center of the macula.
Photodynamic therapy was developed, and I played a major role in its development, to try and come up with a more selective treatment where you could injure the abnormal blood vessels without hurting the retinal cells. We were able to do that and showed in some large clinical trials that photodynamic therapy was able to reduce vision loss in a large number of patients, and it was the first drug treatment introduced for age-related macular degeneration in 2000 in the United States. We still use it to some extent today, but it's really been supplanted by other treatments that give even better results