Reduction in corneal haze and apoptosis by amniotic membrane matrix in excimer laser photoablation in rabbits

Purpose: To determine whether preserved human amniotic membrane can reduce corneal haze and keratocyte apoptosis induced by excimer laser photoablatio n in rabbit corneas. Methods: Excimer photoablation was performed bilaterally in 30 rabbits with a 6.0 mm ablation zone and 120 mum depth using the VISX Star laser with th e phototherapeutic keratectomy (PTK) mode. One eye was randomly covered by preserved human amniotic membrane secured with 4 interrupted 10-0 nylon sut ures, and the other eye served as the control. The amniotic membranes were removed at 1 week, and corneal haze was graded with slitlamp biomicroscopy by 3 masked corneal specialists biweekly for the ensuing 12 weeks until the rabbits were killed. Another 18 rabbits were divided into 4 subgroups and received PTK alone, PTK with membrane, PTK with sham sutures, or PTK with t arsorrhaphy. All eyes were studied histologically, and 3 eyes in each group were studied by in situ terminal deoxynucleotidyl transferase deoxy-UTP-ni ck end labeling assay at 1, 3, and 7 days and 12 weeks, respectively. Results: A consistent grading of differences in corneal haze scoring betwee n the control corneas and the amniotic-membrane-covered corneas was noted a mong the 3 masked observers. Organized reticular post-PTK corneal haze peak ed at 7 weeks in both groups, and the corneal haze score in the amniotic-me mbrane-covered group was significantly less than in the control group from 7 to 12 weeks tall P < .001). Compared to the control corneas, the amniotic -membrane-covered corneas had less inflammatory response at 1 and 3 days, l ess keratocyte apoptosis in the ablated anterior corneal stroma at 1, 3, an d 7 days (P (.001), and less stromal fibroblast cellularity and epithelial hyperplasia at 12 weeks. Conclusions: Amniotic membrane matrix introduced at an early stage of the c orneal wound healing process effectively reduced corneal haze induced by ex cimer laser photoablation in rabbits. Studies linking suppression of apopto sis in the acute wound-healing process with reduction of subsequent corneal scarring may have useful clinical applications. J Cataract Refract Surg 20 01; 27:310-319 (C) 2001 ASCRS and ESCRS.