Cellular photoablation to control postoperative fibrosis in a rabbit modelof filtration surgery

Aim-To evaluate the feasibility of cellular photoablation using fluorescenc e generated photoreaction products as a method to control postoperative fib rosis. Methods-The fluorescent probe, 2',7'-bis-(2- carboxyethyl)-5- (and-6) -carb oxy-fluorescein, acetoxymethyl ester (BCECF-AM) is a cell membrane permeabl e compound rendered membrane impermeable and fluorescent upon cleavage by i ntracellular esterases. Rabbits (ChB-B:CH; n=20) received a unilateral subc onjunctival injection of BCECF-AAI (40, 70, 80, or 100 mu g) 30 minutes bef ore surgery followed by intraoperative illumination with diffuse blue light (450-490 nm; 51.9x10(3) cd/m(2)) for 10 minutes. Controls received either the probe or illumination. Antifibrotic efficacy was established by clinica l response and histological examination. Clinical response was assessed by comparing intraocular pressure (IOP) between the treated experimental eye a nd the fellow eye, which served as control. Success was defined by >20% dif ference in IOP. Results-IOP was significantly decreased in all groups within 4 days postope ratively. In control groups IOP rose within 10 days to normal levels. This was similar in the group receiving 40 mu g of BCECF-ARI. In the other group s (subconjunctival injection of 70-100 mu g BCECF-AM) IOP was significantly (p < 0.02) decreased for 2-3 weeks. Clinical and histological examination revealed no toxic damage to adjacent tissues. Conclusions-Cellular photoablation in contrast with chemotherapeutic agents acts on cells that have incorporated BCECF-AM and have been exposed to lig ht at the appropriate wavelength. Though safety and reliability demand furt her studies this method might be an useful therapeutic approach to control postoperative fibrosis in humans undergoing filtration surgery.