A Gold Standard for Glaucoma Surgery?

Is trabeculectomy the gold standard for glaucoma surgery? A procedure that can cause dysesthesia and endophthalmitis and will often fail seems an unlikely standard by which to measure all other surgery, but many glaucomatologists believe trabeculectomy is the best we’ve got today.

Trabeculectomy is practiced many different ways, and it often strikes me that the procedure has more variations than cataract surgery. Fornix-based flaps are becoming more common and limbal-based flaps less so. We now understand the importance of placing mitomycin C posteriorly to get a desirable bleb. Scleral-flap size, shape and thickness of the internal aspect of the filtering fistulation, placement and type of stitches, all are major variables. Each glaucoma specialist is convinced that his or her procedure is the correct one, making trabeculectomy anything but standard.

For years, timolol and then prostaglandins were regarded as the gold standard for glaucoma medications, despite their limitations. Most of us now believe the contention of my mentor, Richard Brubaker, that beta-blockers do not affect IOP at night. While they effectively lower IOP during the day, these drugs also have a legendary list of side effects. So, gold standard? Perhaps they are better regarded as a bronze standard or a nominal standard. To think of them as a gold standard suggests they cannot be improved on.

An improved glaucoma surgery needs to do many things: flatten the diurnal curve, eliminating high pressures at night; reduce the risk of infection, avoiding endophthalmitis from the organisms found on the lid margin; and provide an inexpensive, reliable procedure, allowing effective therapy to be deployed in a third-world setting.

Glaucoma surgery is improving, albeit in small and incremental steps, but collectively they are advancing the quality of care. The ExPRESS shunt (Alcon), discussed in this issue by Peter A. Netland, MD, PhD, appears to decrease hypotony and choroidal effusions. The device is particularly safe when combined with several tight stiches in the flap. I always use at least three tight sutures, which I will later laser, and I always use mitomycin C tirated to the characteristics of the tissue. The efficacy of deep sclerectomy, the iScience procedure and the Trabectome (NeoMedix), although variable, are all immediately available means of lowering pressure without creating a bleb. These innovations may have a steep learning curve, and they may not work equally well—that remains to be studied—but none of them leaves the eye with the vulnerability of trabculectomy.

In the future, we will hear more about stents placed in the trabecular meshwork. Multiple stents or some other means may be required to deliver this technology to several clock hours of meshwork. Suprachoroidal approaches seem likely to become popular soon. A future, more reproducible type of trabeculectomy may still create a bleb but is likely to have very different characteristics.

New technologies need to be measured against one other, against historical controls and even against trabeculectomy. Trabeculectomy is performed so differently by each surgeon that we need to make sure we measure innovations against some standard technique.

So, yes, trabeculectomy is the standard against which to measure other technologies, but there is nothing “gold” about it.