Use of Ultrasound Biomicroscopy to Predict Long-Term Outcome of Sub-Tenon Needle Revision of Failed Trabeculectomy Blebs: A Pilot Study

Abstract

Purpose. To evaluate the role of ultrasound biomicroscopy (UBM) in predicting the long-term outcome of sub-Tenon needling revision of failed trabeculectomy blebs. Methods. Adult patients with a failed trabeculectomy bleb and unsatisfactory intraocular pressure (IOP) control were recruited. The aqueous flow under the partial thickness scleral flap was looked for and the blebs classified on UBM as scleral route patent (SRP) or scleral route occluded (SRO). All blebs underwent needling revision with injection of 5 mg/0.1 mL 5-fluorouracil. Survival of the revision procedure at the end of 2 years follow-up with regards to the baseline UBM characterization of the bleb was noted. Successful outcome was defined as IOP <22.0 mmHg and/or 30% reduction of baseline IOP with or without medication. Results. A total of 13 eyes had SRP and 5 eyes had SRO blebs on UBM. Only SRP blebs survived the needling procedure by the end of 2 years. Of the 13 SRP blebs, 10 blebs survived (76.9%). Needling had failed in all 5 SRO blebs. The overall success rate was 55.6 % at 2 years. There was no difference in age, IOP, and time from initial trabeculectomy between the failed and successful group. The outcome correlated significantly to the patency of the scleral route assessed by UBM (p=0.07). Conclusions. Ultrasound biomicroscopy characterization of failed blebs appears to help in predicting the outcome of needle revision. In SRO blebs, it may be better to plan a full bleb revision rather than needling alone. Ultrasound biomicroscopy may help in avoiding an unnecessary needling procedure in SRO blebs where it is likely to fail.