What is photodynamic therapy, or PDT?
Intravenous dye (Visudyne) is used, followed in 15 minutes by a low dose, broad area laser for a few minutes. The dye concentrates in new vessels, and the laser interacts with the dye to produce singlet oxygen which selectively damages abnormal vessels. Note that in this case the laser is at a frequency not thought to harm the retina; therefore PDT can be used to treat lesions under the macula without the possible immediate central or side vision loss incurred in traditional laser treatment.
