Safety and efficacy of photodynamic therapy using BCECF-AM compared to mitomycin C in controlling post-operative fibrosis in a rabbit model of subscleral trabeculectomy.

AIM

To evaluate the safety and efficacy of cellular photoablation using BCECF-AM [2', 7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester mixed isomers] as a method to control postoperative fibrosis in subscleral trabeculectomy (SST) compared to mitomycin C (MMC) in a rabbit model.

METHODS

A comparative prospective case-control animal study was conducted. Fourteen rabbits were subjected to SST with intraoperative use of wound modulating agents (MMC or BCECF-AM) of the right eye (study groups I and II respectively) and SST without use of intraoperative wound modulating agents for the left eye (control group II). Two rabbits 4 eyes were considered as control group I with no surgical intervention. BCECF-AM was injected subconjunctivally 30min before surgery followed by intraoperative illumination with diffuse blue light for 10min. Antifibrotic efficacy was established by clinical response and histological examination. Clinical response was assessed by measuring intraocular pressure (IOP) at day 1, 3, 5, 7, 14, 21 postoperatively. Success was defined by >20.0% reduction in IOP from the preoperative values without anti-glaucoma medications.

RESULTS

The mean percentage of reduction was 35.0% in the study group I with only one eye (14.3%) had 12.5% reduction. The mean percentage of reduction was 28.0 % in the study group II with two eyes (28.6%) in study group II had 14.2% reduction each. Regarding the control group II, the mean percentage of reduction was 14.3 % with 64.3% eyes had <20.0% reduction. There was a highly statistically significant difference between each of the study groups (right eyes) and the corresponding control group II (left eyes) as regards the mean postoperative IOP values started from day 5 in both study groups and this highly significant difference remained so till the end of the follow up period. Histologically, MMC treated blebs showed thinning of conjunctival epithelium with marked reduction of the goblet cells relative to control. Marked sub-epithelial edema was seen along with variable collagen dispersion. Mild cellularity was noted in sub-epithelial tissue. BCECF-AM treated blebs showed normal conjunctival epithelial thickness with abundant goblet cells. Mild sub-epithelial edema was noted along with moderate collagen dispersion. No histological abnormality was noted in the ciliary body or the cornea in any of the studied groups.

CONCLUSION

Cellular photoablation using BCECF-AM is a safe and effective wound modulating agent to control postoperative fibrosis in trabeculectomy. However MMC considered as a more potent adjuvant to trabeculectomy than BCECF-AM in promoting IOP reduction.