Photodynamic therapy: ICG angiographic findings

Purpose: Photodynamic therapy (PDT) has been shown to provide immediate occlusion of choroidal neovascularization (CNV), followed by recurrent leakage after single PDT in the majority of the cases after 3 months. Indocyanine green angiography (ICG-A) was used to evaluate completeness of CNV occlusion, effects on physiological choroid and patterns of CNV recurrence. Methods: ICG-A was performed using a confocal laser scanning ophthalmoscope (HRA) before PDT at 1 week, 4 and 12 weeks following PDT. Twenty patients with single and 10 patients with repeated PDT treatments with administration of benzoporphyrin derivative and radiant exposures between 50 and 150 J/cm² were evaluated. Results: Before PDT well-defined CNV was detectable during early ICG-A in all lesions. Depending on the number of treatments, CNV was absent in early phase ICG-A in 46–83 %. CNV reappeared at week 4 in many and at 12 weeks in 77 (66 %) of the cases. The treated area regularly showed hypofluorescence, which persisted until week 12. The intensity of choroidal hypofluorescence showed wide interindividual variability. Recurrence may originate from persistent feeder vessels. Conclusion: With ICG-A we demonstrated that PDT induces hypofluorescence of CNV and choroid possibly due to perfusion changes or blockade phenomena. Recurrence may be due to reperfusion of the preexisting CNV or regrowth from feeder vessels.