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Editors Selection IGR 19-2

Surgical Treatment: Drainage devices 1

Comment by Robert Feldman on:

55325 Randomized, prospective, comparative trial of EX-PRESS glaucoma filtration device versus trabeculectomy (XVT study), Netland PA; Sarkisian SR; Moster MR et al., American Journal of Ophthalmology, 2014; 157: 433-440.e3

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The authors compared in a randomized non masked (neither investigator, nor patient, nor IOP reader) fashion the success of trabeculectomy with or without express shunt and found no long term differences in outcome. They report faster visual recovery with the express returning to baseline within a month and it taking three months for a trabeculectomy. Also, the overall complication rate for the trabeculectomy group was higher. There are some issues, however, that cloud the conclusions and potentially bias the results.

1) There was no masking of IOP readings, and no standardization of the surgical methods. In fact, the conjunctival flap type appears to be different between groups although it was not detected statistically due to lack of power.
2) The success criteria is also a little suspect. Having failures based on IOP occurring during the first three months postop is not a reasonable criteria as trabeculectomies often take this long to stabilize IOP for the long term. In fact, suture lysis is often not completed for a month or so postoperatively, failing these eyes early will lead to cumulative failure rates higher than true failures. 3) The complication rate was driven purely by hyphemas and shallow chambers, but there was no difference in the shallow chambers requiring intervention which would be a better measure given lack of masking nor standard definition of a shallow chamber. Despite these shortcomings and potential biases, the study was unable to find a clinically important difference between these two procedures.

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