Dose-Related Structural Effects of Photodynamic Therapy on Rabbit Choroidal Structure

Abstract

Introduction: Photodynamic therapy with verteporfin (vPDT) has been shown to be effective against central serous chorioretinopathy (CSC) and was the preferred therapeutic for CSC treatment. However, alterations in choroidal structure after PDT were reported, and these effects were dose-dependent. This study aimed to compare the changes in choroidal structure after PDT with different doses of verteporfin in rabbits and may provide individualized therapeutic guidance for patients who failed to respond to initial half-dose vPDT. Methods: The full dose of verteporfin used in CSC was 6 mg/m², which was used in patients with neovascular age-related macular degeneration. Laser fluence was 50 J/cm² (irradiance, 600 mW/cm², 83 s). There were 4 different dose groups in this study (100%, 70%, 50%, and 30%). The alterations were examined at 1 day, 1 week, and 1 month after vPDT using color fundus imaging, indocyanine green angiography, and histopathology analysis. Results: Various degrees of choroidal alterations were demonstrated at different dose groups. Examinations on day 1 showed that gradually reduced verteporfin dose tended to decrease photochemical reactions to the choroid in terms of the number of occlusion vessels and area of the lesion. After 1 month, choroid vessel alteration persisted in high-dose groups (100% and 70%); nevertheless, alterations of low-dose groups (50% and 30%) returned to normal. Conclusions: vPDT can induce photochemical reactions of the choroid, high dose causes permanent change, and low dose causes recoverable change. The dose-dependent alterations need to be considered for the individual therapeutic plan according to the situation of a patient with CSC.