MAR 11, 2011
The authors conducted this retrospective case series to determine whether previous phacoemulsification adversely affects the outcome of trabeculectomy with mitomycin in eyes with open-angle glaucoma (OAG). They conclude that previous cataract surgery, even when a smaller conjunctival incision is employed, is a significant prognostic factor for surgical failure of trabeculectomy with mitomycin for OAG.
Subjects in the study were 226 consecutive patients (226 eyes) with primary OAG or exfoliation glaucoma undergoing initial trabeculectomy at one of two hospitals. The pseudophakic group included eyes with previous phacoemulsification and posterior chamber IOL implantation that involved a superior conjunctival incision. Follow up was a mean of 37.5 months.
The probability of success, defined as a need for additional glaucoma surgery or IOP of 21 mmHg or greater, at one year was 97.8 percent in the phakic group and 92.6 percent in the pseudophakic group and at three years was 78.6 percent and 65.1 percent, respectively (P < 0.001). Statistical analysis indicated that pseudophakia and higher preoperative IOP each independently contribute to surgical failure. Significantly more of the pseudophakic patients required postoperative laser suture lysis (60.8 vs. 41.1 percent; P = 0.01). They also required a significantly greater number of glaucoma medications at six and twelve months than the phakic group (P < 0.001 for both), although this difference was not significant at 24 months or later after trabeculectomy.
Several reports in the literature have indicated that eyes with previous conjunctival incisions or intraocular surgical procedures before trabeculectomy have poor prognosis. One possible explanation is the increased number of conjunctival fibroblasts and inflammatory cells in pseudophakic eyes. Another explanation is the alteration of the nature of aqueous humor due to the breakdown of the blood-aqueous barrier after previous intraocular surgery. Also fibroblast chemoattractant activity might be increased in aqueous humor after phacoemulsification, thereby promoting subconjunctival fibrosis after trabeculectomy. Further studies are necessary in order to understand which mechanisms cause surgical failure of trabeculectomy in pseudophakic eyes.