INHIBITION OF EXPERIMENTAL CHOROIDAL NEOVASCULARIZATION WITH TRANSPUPILLARY THERMOTHERAPY

Abstract

Abstract: : Purpose. To evaluate the histological and ultrastructural findings after transpupillary thermotherapy (TTT) of experimental choroidal neovascularization (CNV) using visible and non–visible thermal burns. Methods. CNV was induced in 37 pigmented C57BL/6 mice using a krypton laser where after TTT (power 50, 60 or 80 mW, spot size 1.2 mm, duration 60 s) was delivered to the CNV lesions using a diode laser (emission wavelength 810 nm) and a slit lamp delivery system with a handheld contact lens. Eyes were enucleated 13 days after CNV induction andhematoxylin–eosin stained paraffin embedded sections prepared. Five to 10 serial sections from each CNV complex were measured and the highest value was stored. Ultrastructural changes in the TTT treated CNV lesions were analyzed by transmission electron microscopy. Results. TTT treatment with a power of 50 mW gave no visible effect on the retina whereas treatment with a power of 80 mW resulted in retinal whitening. When TTT was applied over the laser–induced CNV lesions the height of lesions was significantly reduced (p < 0.001) using all three power settings (50 mW, 60 mW and 80 mW). The overlying neural retina showed no apparent damage with the 50 mW or 60 mW settings whereas complete disruption of the outer nuclear layer was seen with a power of 80 mW. Ultrastructural studies confirmed that vascular occlusion was present at 24 h after TTT and that a fibrotic scar was later formed. Conclusions. The results show that TTT can effectively occlude newly formed vessels and decrease the experimental CNV complex without damaging the neural retina.

Keywords: age–related macular degeneration • choroid: neovascularization • laser