Transient Increase of Permeability in Experimental Choroidal Neovascularization after Transpupillary Thermotherapy

Abstract

Abstract: : Purpose: It was reported that transpupillary thermotherapy (TTT) could decrease exdation in choroidal neovascularization (CNV). In the present study, we evaluated changes of permeability in CNV after TTT. Methods:A modified slit lamp, which was installed with two laser wavelenghs (490 nm for illumination and fluorescein excitation and 810 nm for hyperthermia), was developed for TTT. Following TTT (0, 2, or 4 minutes) on rat CNV with the modified slit lamp, fundus angiography was observed on time 0, 2, 4, 6, 12, 24, 48 and 72 hours. Fundus angiography was performed with the slit lamp after intravenous injections of Fluorescein isothiocyanate–dextrans (FD), whose molecular weights were 4kd (FD4) or 70kd (FD70) respectively. Angiographic images were converted to 256 gray scales. Permeation of macromolecules from CNV was calculated as fluorescein intensity ratio of selected lesions of CNV to backgrounds. Results:We observed increase of permeability of 70kd macromolecules after TTT, and the increase depended on TTT duration. Accumulation of FD70 around CNV significantly increased from time zero to 12h, in eyes administered TTT for 4 minutes. However, accumulation of FD70 in eyes with TTT for 2minutes did not increase. Accumulation of FD4 around CNV did not correlated with TTT duration. Conclusions:Our results showed that permeability changes of CNV after TTT depended on molecular size or duration of TTT. This suggested a potential that we could control delivery of macromolecular drugs to CNV with TTT.

Keywords: age–related macular degeneration • laser