Hypotony After Trabeculectomy with Mitomycin C

ABSTRACT

The purpose of this study is to evaluate the influence of clinical factors on the development of postoperative hypotony, and also to determine whether the occurrence of hypotony has any effect on the outcome of trabeculectomy with intraoperative mitomycin C. The authors retrospectively reviewed the outcome in 160 eyes of 112 patients who underwent tight scleral flap trabeculectomy with releasable sutures. Mitomycin C with 0.25 or 0.5mg/ml was applied for 3 or 5 minutes between the Tenon's capsule and the sclera. The mean follow-up period was 16.5 +/- 11.5 months. Success of the trabeculectomy was defined as intraocular pressure (IOP) 6-21 mmHg with or without medications. Hypotony(IOPeyes(21.3%) at some point postoperatively between 1992 and 1995. The hypotony was prolonged (more than 15 days-group 1) in 8 eyes, transient (less than 14 days-group 2) in 26 eyes, and not developed in 126 eyes(control group), The duration of hypotony was less than three weeks except for two eyes. The both groups with hypotony were younger and more myopic than the control group but it did not reach statistical significance(p=0.13, p=0.27, respectively). There was a trend toward increased incidence of hypotony with higher concentration of mitomycin C. There was no difference in the incidence of hypotony between uncomplicated glaucoma and refractory glaucoma(p=0.92). Postoperative hypotony was associated with three types of postoperative complications; shallow anterior chamber, wound leakage, and choroidal detachment(p=0.0001, 0.0001, and 0.004, respectively). There were no statistically significant differences in cataract formation(p=0.40) and change in final visual acuity(p=0.52) among groups. Eighteen months after surgery, IOP was controlled successfully in 87.5% in the group 1, in 84.6% in the group 2, and in 89.7% in the control group without significant difference. The number of glaucoma medications was not significant among group(p=0.24). In our study, postoperative hypotony less than three weeks did not cause any significant adverse effect in the outcome of trabeculectomy with mitomycin C. However, since there are possibilities of various complications as the duration of hypotony becomes longer, caution in avoiding the accurrence of hypotony is adviced.