Abstract
Abstract: :
Purpose: To determine the prophylactic effect of photodynamic therapy (PDT, Visudyne) on the induction of choroidal neovascularization (CNV) and to assess whether combination therapy of PDT with threshold argon laser increases the chances of CNV. Methods: 24 Long Evans rats (1 eye each) used for this study were treated in accordance with the ARVO resolution on the care and use of animals in research under a protocol approved by the IACUC. Four eyes were used to determine the threshold parameters of PDT. Diode laser at a wavelength of 689 nm and irradiance of 600 mW/cm2 was applied for 25, 50, 75 and 100 sec, 1 min after intravenous injection of 0.5mg/kg of Visudyne. Fluorescein angiography was used to determine the threshold lesion. Parameters for the threshold lesion were used thereafter. Part 1, 4 eyes were treated with 4–8 PDT lesions at the threshold parameters; these areas were treated within 24 hr with bursting argon laser lesions at parameters titrated to produce Bruch’s membrane breaks at 300–400 mW, spot size 50 µm for 0.05 sec. Four eyes were used as controls with bursting lesions without prophylactic PDT lesions. Part 2, 4 eyes were treated with 4–8 PDT lesions at the pre–determined threshold parameters. These lesions were treated within 24 hr at threshold non–bursting argon laser lesions. Four eyes received 4–8 threshold PDT lesions; another 4 eyes received threshold non–bursting laser lesions. Fluorescein angiography was performed 14 days after the lesions were placed to assess for CNV in all groups; the animals were sacrificed and the eyes prepared for histology. Results: Part 1 demonstrated laser–induced CNV in all 8 eyes that received bursting argon laser lesions with or without prophylactic PDT. The extent of CNV was the same in both groups. Part 2 found no CNV in eyes which received combination treatment of PDT with threshold argon laser, PDT laser alone, or threshold argon laser alone. Conclusions: Prophylactic PDT does not enhance or suppress laser–induced CNV. Furthermore, combination treatment of PDT with threshold (non–bursting) argon laser does not by itself create CNV.
Keywords: photodynamic therapy • laser • choroid: neovascularization