Cellular photoablation to control postoperative fibrosis in a rabbit model of filtration surgery

To evaluate the feasibility of cellular photoablation using fluorescence generated photoreaction products as a method to control postoperative fibrosis.

The fluorescent probe, 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester (BCECF-AM) is a cell membrane permeable compound rendered membrane impermeable and fluorescent upon cleavage by intracellular esterases. Rabbits (ChBB:CH; n=20) received a unilateral subconjunctival injection of BCECF-AM (40, 70, 80, or 100 microg) 30 minutes before surgery followed by intraoperative illumination with diffuse blue light (450-490 nm; 51.9 x 10(3) cd/m(2)) for 10 minutes. Controls received either the probe or illumination. Antifibrotic efficacy was established by clinical response and histological examination. Clinical response was assessed by comparing intraocular pressure (IOP) between the treated experimental eye and the fellow eye, which served as control. Success was defined by >20% difference in IOP.

IOP was significantly decreased in all groups within 4 days postoperatively. In control groups IOP rose within 10 days to normal levels. This was similar in the group receiving 40 microg of BCECF-AM. In the other groups (subconjunctival injection of 70-100 microg BCECF-AM) IOP was significantly (p < 0.02) decreased for 2-3 weeks. Clinical and histological examination revealed no toxic damage to adjacent tissues.

Cellular photoablation in contrast with chemotherapeutic agents acts on cells that have incorporated BCECF-AM and have been exposed to light at the appropriate wavelength. Though safety and reliability demand further studies this method might be an useful therapeutic approach to control postoperative fibrosis in humans undergoing filtration surgery.