Methylcellulose, a healing inhibitor factor in an animal model of trabeculectomy.

PURPOSE To use an experimental animal model to study the effect on intraocular pressure (IOP) of methylcellulose 2% application in trabeculectomy, followed by histologic assessment. METHODS Trabeculectomy was performed on albino rabbits' eyes. The study comprised two groups, each group consisting of five rabbits. The right eyes were subjected to trabeculectomy, and the left eyes served as the control. In both groups 1 and 2, trabeculectomy was performed in the right eyes, but in group 2, trabeculectomy was followed by injection of methylcellulose 2% into the anterior chamber. The methylcellulose was allowed to pass through the trabeculectomy site into the subconjunctival space, and an extra amount was injected by the same cannula under the conjunctiva in the area of the trabeculectomy from the edge of the periotomy. Measurement of IOP was performed with a Shiotz tonometer once weekly for 4 weeks. Specimens were obtained from the operative site, and semithin sections were prepared, stained with toluidine blue, and examined by light microscopy (LM). RESULTS A significant difference in the decrease of IOP (P<0.0001) was observed between the two groups after 4 weeks of surgery. During the 4 weeks after trabeculectomy, the mean IOP was 18.2+/-0.45 mm Hg without methylcellulose injection and 18.3+/-0.77 mm Hg in the control eyes, and 9.8+/-0.84 mm Hg with methylcellulose injection, 18.25+/-0.7 mm Hg in the control eyes. The histopathological findings in group 1 (without methylcellulose injection) showed the subscleral spaces to be less fenestrated, with deposition of dense collagen bundles intermingled with the fibrocytes, some of which were active with prominent mitosis. In contrast, in group 2 (injected with methylcellulose), the subscleral space appeared fenestrated with irregularly and widely spaced segmented collagen bundles. CONCLUSIONS Methylcellulose may have antihealing properties that serve to decrease IOP in trabeculectomy. Although more work is needed in humans, because human tissue may be different in its response to the same procedure, the use of methylcellulose could be very promising.