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    Glaucoma

    Review of: Outcomes of the Shunt Tube Exposure Prevention Study

    Sheha H, Tello C, Al-Aswad L, et al. Ophthalmology Glaucoma, November–December 2019

    This prospective clinical trial compared the long-term safety and efficacy of amniotic membrane-umbilical cord (AM-UC) and pericardium patch grafts for reducing glaucoma shunt tube exposure.

    Study design

    A total of 81 eyes were randomized to Baerveldt (n=72) or Ahmed (n=9) valves with either AM-UC (n=41) or pericardium (n=40) patch grafts to cover the tube. Researchers used anterior segment OCT to assess patch graft stability and host-tissue integration, with a focus on tube exposure, graft thinning, and graft-related complications.

    Outcomes

    Patients were followed an average of 29 months. Sequential anterior-segment OCT showed better host-tissue integration and significantly less graft thinning in the AM-UC group than in the pericardium group. Five eyes (12%) in the AM-UC group and 17 (43%) in the pericardium group experienced early graft thinning within 3 months of surgery (P=0.002). Late thinning occurred in 2 AM-UC eyes and 11 pericardium eyes (P=0.007). Graft translucency and cosmetic appearance were superior in the AM-UC graft group. Overall, infection and graft rejection did not correlate with graft type.

    Limitations

    The major limitations of this study are the variable follow-up durations and inability to measure the pericardium with anterior segment OCT. The follow-up period ranged from 13 to 40 months and it unclear how long each group was followed. The lack of pericardium thickness measurements limited the comparisons to AM-UC thickness. Without the measurements, it is difficult to see the relevance in using anterior segment OCT to compare the grafts. It would have been useful to have the pre- and postoperative graft thickness measurement. Instead of pericardium, it may be preferable to use a graft material that could be reliably measured with this OCT method. Cost comparisons could provide context.

    Clinical significance

    Amniotic membrane-umbilical cord grafts have potential benefits based on their high-tensile strength, low immunogenicity and host-tissue integration potential. This randomized, controlled trial, however, has not provided convincing evidence to encourage use of this graft over other comparable options.