May 01, 2009
4 min read

Tube Versus Trabeculectomy Study

At Issue posed the following question: Has the TVT study influenced your indications for tube shunt surgery?

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New filtering procedure still a consideration

Stefano A. Gandolfi, MD: The TVT study has not influenced my indication for tube shunt surgery. In fact, the follow-up data are limited to a 1-year time frame.

Besides, the efficacy results are comparable in both treatment arms. The reported incidence of sight-threatening adverse events deserves some attention: A 57% complication rate (and 28% loss of more than two Snellen lines of visual acuity) after a trabeculectomy does exceed immensely what is routinely experienced by any glaucoma specialist, at least (a) in Europe and (b) upon adoption of the “safe trabeculectomy” strategy developed by Peng Khaw in Moorfields. On the contrary, a 1-year follow-up is by far too short for evaluating the most common tubes-related serious adverse event, ie, corneal decompensation.

Therefore, after a failed trabeculectomy, I still consider a new filtering procedure as a primary option, shifting to a tube in case the limbal conjunctiva appears in a very poor condition (ie, scarred, contracted, shortened, etc.). Moreover, new procedures are being currently investigated in refractory glaucomas (for example, the Gold Shunt, the trabecular-micro bypass, etc). Their indication must be considered when offering the possible surgical options to a high-risk patient bearing a failed trabeculectomy.

  • Stefano Gandolfi, MD, can be reached at the University of Parma, Department of Ophthalmology, Via Giuseppi Rossi 28, 43100 Parma, Italy; +39-521-259-103; e-mail:

Longer follow-up needed

Ivan Goldberg, MBBS, FRANZCO, FRACS: While the TVT study results are most interesting, to date they have not influenced my recommendations to patients needing glaucoma surgery. To make the study’s results more meaningful clinically to the patients I care for, what is needed is longer follow-up and a broader range of patients selected for randomization.

I have been inserting glaucoma drainage devices since 1984. For many patients in whom trabeculectomy has proven most disappointing (such as poorly controlled uveitis with secondary glaucoma, patients with the iridocorneal endothelial syndrome or closed-angle glaucoma from neovascularization), these devices have been most helpful.

Unfortunately, however, they are not without problems. Leaving aside the short-term postoperative challenges through which most patients can be navigated successfully, longer-term problems remain a serious challenge. In particular, problems include corneal endothelial failure and decompensation and thick encapsulation around the plate(s), leading to rising IOP and late tube erosion through the conjunctiva.

Corneal decompensation can occur even with no physical tube/endothelial contact. Late-rising IOP is unavoidable with current knowledge and technologies. Tube erosion occurs even decades later despite scleral trapdoors and overlying graft material. Even 3-year study results cannot capture some of these problems with tubes, underlining the “curse” that is long-term follow-up in glaucoma.

For each patient, the clinician needs to balance immediate needs for IOP control against long-term complications with any suggested surgical route. No one study, no matter how good, should influence unduly the considerations of this balance.

  • Ivan Goldberg, MBBS, FRANZCO, FRACS, can be reached at 187 Macquarie St., Park House, Floor 4, Suite 2, Sydney NSW 2000, Australia; +61-2-9247-9972; fax: +61-2-9232-3086; e-mail:

Already using shunts more

Nathan G. Congdon, MD, MPH: The TVT study’s two main publications suggest that the Baerveldt tube shunt may be at least as safe and effective as trabeculectomy surgery among patients with previous surgery (which might only include phacoemulsification).

This is a group of patients for whom many glaucoma specialists might have performed trabeculectomies in the past. I expect that these results will likely accelerate a trend which had already seen trabeculectomies decline by 53% and tube shunts increase by 184% among Medicare beneficiaries in the decade prior to the TVT. The fact is that prior to the TVT, I was already performing more tube shunts than trabeculectomies, probably an indication of the tertiary-care nature of my practice as much as anything else.

However, I think there are some issues worth considering in deciding to perform tube shunt vs. trabeculectomy surgery in the post-TVT world.

In the first place, the basic message of TVT from my perspective was one of equivalency between the procedures. In patients where either procedure would do, I think that we ought to have a specific justification for using a several hundred dollar device where similar results might be achieved without one. While some of us may associate such thinking with “bean counters” and resent its intrusion into clinical practice, in a world where every trend (an aging population, the constant discovery of new procedures and medications) mandates rising medical costs, it is increasingly responsible and appropriate that we as physicians do what we can to hold costs down.

The TVT was conceived and directed by some of the most respected names in academic glaucoma, participants were drawn from the top clinical centers, and the results published in outstanding peer-reviewed journals. We take nothing away from any of these individuals and institutions when we remind ourselves that the TVT was funded in part by the manufacturer of the Baerveldt shunt.

A recent study of postoperative adverse outcome after glaucoma surgery among Medicare beneficiaries has reported a significantly higher incidence of endophthalmitis, retinal detachment and blindness among patients receiving tube shunts as compared to filtration surgery, with the differences widening over 6 years of follow-up. As the authors themselves point out, these results may reflect unmeasured differences in case severity between the two surgical groups, but they certainly bear further investigation.

I continue to perform a large number of tube shunt surgeries in my practice, but now, as before the TVT, I weigh my options carefully before deciding to proceed with a drainage device.


  • Ramulu P, Corcoran KJ, Corcoran SL, Robin A. Utilization of various glaucoma surgeries and procedures in Medicare beneficiaries from 1995 to 2004. Ophthalmology. 2007;114(12):2265-2270.
  • Stein JD, Ruiz D Jr., Belsky D, Lee PP, Sloan FA. Longitudinal rates of postoperative adverse outcomes after glaucoma surgery among Medicare beneficiaries 1994-2005. Ophthalmology. 2008;115(7):1109-1116.

  • Nathan G. Congdon, MD, MPH, can be reached at the Department of Ophthalmology and Visual Science, Chinese University of Hong Kong; e-mail: