Outcomes of the Shunt Tube Exposure Prevention Study: A Randomized Clinical Trial

Purpose: To compare the long-term safety and efficacy of amniotic membrane-umbilical cord (AM-UC) and pericardium patch grafts in reducing glaucoma shunt tube exposure.

Design: Multicenter, prospective, randomized clinical trial.

Participants: Adults with uncontrolled glaucoma undergoing glaucoma drainage device (GDD) implantation.

Methods: Patients were randomized to receive GDD with either AM-UC or pericardium patch grafts to cover GDD tubes. Patients were followed up clinically with anterior segment (AS) OCT to assess patch graft stability and host-tissue integration prospectively.

Main outcome measures: Tube exposure, graft thinning, and graft-related complications.

Results: A total of 81 eyes of 81 patients (50 women, 31 men) with a mean age of 67±13 years underwent GGD implantation using Baerveldt (n = 72) or Ahmed valve (n = 9). Tubes were inserted in the anterior chamber (n = 71), sulcus (n = 6), or pars plana (n = 4). Tube ligation was performed with Baerveldt GDD along with fenestration (n = 51) or orphan trabeculectomy (n = 21). Tubes were covered with AM-UC (n = 41) or pericardium (n = 40). The mean follow-up time was 29±8 months (range, 13-40 months). Tube exposure occurred in 1 eye (2%) in the AM-UC group at 3 months and in 2 eyes (5%) in the pericardium group at 2 and 6 months (P = 0.54). Sequential AS OCT showed better host-tissue integration and significantly less graft thinning in the AM-UC group. Early graft thinning (≤3 months) occurred in 5 eyes (12%) in the AM-UC group and in 17 eyes (43%) in the pericardium group (P = 0.002). Late thinning occurred in 2 eyes (5%) and 11 eyes (28%) in the AM-UC and pericardium groups, respectively (P = 0.007). Graft translucency and cosmetic appearance of the AM-UC graft were superior to those of the pericardium graft. No evidence of graft rejection or infection was associated with the patch grafts in either group.

Conclusions: Amniotic membrane-umbilical cord grafts are well tolerated and offer an alternative to pericardium for safe and stable tube shunt coverage. Its high-tensile strength, low immunogenicity, and excellent host-tissue integration significantly reduced graft thinning.