Looking at Glaucoma Surgery
(Note that this was commentary originally authored in 2011-2012)
We used to have weekly morning case rounds during my fellowship at Massachusetts Eye and Ear Infirmary. Whenever we discussed a patient who had intraocular pressure (IOP) uncontrolled on medications, one of the favorite questions asked by my glaucoma fellowship director, David L. Epstein, MD, was, “Why not give them the cure?” His point, of course, was that there was (and is) no cure for our patient with glaucoma. Surgery is a treatment for the disease, more potent but also more risky than medications or laser.
I have frequently thought about the need for improvements in surgical intervention. Notwithstanding that, given the complications associated with our traditional surgical techniques, we have done well with postoperative care. Having trained in the era of full-thickness glaucoma surgery in Boston at a time before the use of mitomycin C (MMC) in the United States, a time during which patients were routinely kept hospitalized postoperatively and when flat anterior chambers and choroidal effusions were commonplace, I did, and do, feel comfortable with my postoperative choices and ability to manage anything manifested by the patient.
Despite my knowledge and comfort with postoperative glaucoma management, I am extremely respectful of the risks attendant to glaucoma surgery. Although we almost always improve the patient’s lot in the long run, there are still a few whose vision is compromised related to our intervention, even when everything goes perfectly intraoperatively. A sneeze, a cough, a slip on the stairs—suprachoroidal hemorrhage is forever an unwelcome guest who shows up at the worst possible time. The patient who calls with intense, aching pain and knows the minute that the pain began, is the one who is telling you that he or she has had bleeding into the suprachoroidal space.
Postoperative complications are an impetus for the current push toward better glaucoma operations. It has been more than 100 years that we have been bypassing the conventional outflow system one way or another. The surgery has gotten progressively more controlled intra- and postoperatively, going from full-thickness surgery to guarded filtration surgery, then later with the use of steroids and antimetabolites. We have even improved glaucoma drainage devices (GDDs) to the point where they are often considered a first-line surgical option, but we only recently advanced glaucoma surgery to focus on improvement of trabecular meshwork (TM) and Schlemm’s canal (SC) inner wall outflow or removal or bypass of TM and SC inner wall.
Schlemm’s canal surgery, including ab interno trabeculectomy, canaloplasty, and TM-SC bypass, is another step toward safety and control in glaucoma IOP reduction surgery. It is less risky than trabeculectomy or GDD implantation, but it is also less effective at IOP reduction. The trade-off of efficacy for safety may be acceptable in patients needing mid- to high-teens IOP, but patients requiring a very low IOP still need more invasive procedures like trabeculectomy or GDD.
Another aspect of the TM-SC bypass or removal procedures is actual surgical access to TM and Schlemm’s canal. Perhaps the movement towards less risky and invasive surgery will have as a byproduct treatment of glaucoma through extended-release medication, cell-based or gene therapy applied directly in Schemm’s canal or the TM.
Maybe, as such treatments emerge, Dave Epstein’s suggestion to “give them the cure” will finally be said without irony.