General Ophthalmologists and Glaucoma Surgery

Some procedures require a more complex skill set.

BY ANDREW RABINOWITZ, MD

As the glaucoma specialist for a large multifacility practice, I have tended to come down on the side of leaving most glaucoma surgeries in the hands of those ophthalmologists who have the training and experience to appropriately deal with the risks that these procedures entail.

The serious risks associated with glaucoma surgery — primarily in the form of too low IOP too soon or too high IOP postop — constitute complex scenarios that warrant either broad experience with these procedures or the availability of a glaucoma specialist who is skilled in managing postops. Any glaucoma specialist can testify to the unsettling effect of seeing the disastrous consequences of hypotony a complication that can occur so quickly that the surgeon can do little to mitigate the situation.

However, given the recent advances in glaucoma surgery many general ophthalmologists will want to add these procedures to their arsenal. This article will discuss the skills required for general ophthalmologists to perform a variety of glaucoma surgeries.

Laser Procedures Are Least Difficult

The management of glaucoma by general ophthalmologists has been a standard medical practice for decades. All general ophthalmologists have great comfort prescribing pharmacologic therapy. When that approach is deemed inadequate, there are several additional treatment paradigms that can be deployed. These include peripheral laser iridotomy and laser trabeculoplasty.

I believe that a large majority of ophthalmologists are properly trained and adept at performing these laser procedures in a successful manner. Knowing the limitations of specific laser wavelengths when applied to specific patient populations is developed over time as the physician hones his or her skills. I have every comfort in generalists performing these laser procedures on a broad base of patients.

Selective laser trabeculoplasty opens up the trabecular meshwork to facilitate outflow.

More Complex Procedures

When laser treatments are ineffective, either as stand-alone treatments or as adjunctive treatments to medical management, physicians are faced with the consideration of glaucoma surgery. The most common glaucoma surgeries are trabeculectomy, aqueous shunt placement, the Ex-Press Mini Glaucoma Shunt, canal-based surgeries and the newer procedures that are designed to remove the wall of Schlemm's canal such as the Trabectome, or whose aim it is to place a stent between the anterior chamber and Schlemm's canal directly.

As far as the skill set needed to perform any of these procedures, it is my opinion that a gifted surgeon can learn any surgery he or she is truly interested in performing. In many rural areas of the United States, the high-volume cataract/anterior segment surgeon is often also the most highly skilled “glaucoma surgeon” within hundreds of miles. There may be fellowship-trained glaucoma doctors within the geography of that general ophthalmologist, but often the high-volume cataract surgeon is more facile when it comes to all procedures, including glaucoma surgeries.

It is definitely a great advantage when a cataract surgeon is also skilled at performing trabeculectomies, as the ability to do a combined cataract removal/glaucoma surgery procedure can be a benefit to certain subset of patients. It should be noted that a combined procedure does carry additional risk and should only be attempted by surgeons who have developed a high level of skill in performing both the phaco procedure and trabeculectomy.

The cataract surgeon who can do a combined cataract and glaucoma procedure can offer these primarily senior — and often fragile — patients a highly effective intervention that requires only one trip to the operating room.

That being said, combined cases are performed far less frequently today than a decade ago. This is because we have found the benefits of each procedure are achievable with greater certainty when the procedures are performed in a staged fashion.

The combined procedure does improve patients' vision. However, the patient's visual recovery is slower after cataract/trabeculectomy than with cataract surgery alone. If a patient has advanced glaucoma with an intraocular pressure that is not being controlled heading into the cataract surgery, the combined event offers the patient a better opportunity to both improve vision and control IOP.

When comparing the combined procedure to cataract surgery alone, patients will often need fewer glaucoma medications after combined surgery. In addition, controlling IOP after the combined procedure tends to be an easier task.

All of this is not said to speak negatively about glaucoma surgery by glaucoma specialists, but rather to state that there are likely hundreds of general ophthalmologists performing high-level glaucoma surgery on a daily basis in the United States. In the case of a less “gifted” surgeon, whether a glaucoma specialist or a generalist, it is better that they limit the types of procedures they perform so as to follow the primary rule of medicine: “First, Do No Harm.”

Trabeculectomy

Most residents have had exposure to some trabeculectomy surgery and an occasional shunt. Few residents leave training having completed large numbers of any surgical glaucoma procedure. That being said, I think that trabeculectomy without anti-metabolites is the glaucoma surgery most commonly performed by the generalist. The success and safety of trabeculectomy is intimately associated with the expertise of the surgeon.

When it comes to using anti-metabolites, 5-FU can also safely be applied by a general ophthalmologist performing glaucoma surgery. The use of mitomycin-C should be cautiously approached by any surgeon who performs glaucoma surgeries on an occasional basis. This warning is due to the risk of inadequate wound-healing both early and late following the use of mitomycin.

Tube Shunts and Complication Risk

The second most commonly performed glaucoma surgery in the United States to date has been the aqueous shunt (Baerveldt, Ahmed, Malteno). These tube shunts, as they are called, have historically been used only after trabeculectomy or trabeculectomy with anti-metabolites fail.

The Ahmed Glaucoma Valve.

Over the past several years, however, they are being used earlier in the treatment cycle and in many cases even before the first trabeculectomy. Because many general ophthalmologists have done only a few of these tube shunts in their training, they often have to take skills-transfer courses and wet labs at the AAO annual meetings. These courses are an excellent way to teach, but the wet-lab setting does not ideally replicate the operating room.

I have had a number of surgeons visit my operating room over the years to spend a morning with me to watch my technique and then return to their operating rooms and try tube shunts on their cases. Their enthusiasm, which is often great at the beginning of their journey, rapidly wanes as they witness the potential complications that can occur following "successful" tube-shunt surgeries. Thus, while I have witnessed generalists perform superb trabeculectomy surgeries, I have witnessed fewer general ophthalmologists maintain enough momentum and enthusiasm to master and continue to perform tube-shunts.

Perhaps the Ex-Press Mini Glaucoma Shunt, recently acquired by Alcon, may serve as a bridge procedure for ophthalmologists interested in glaucoma surgery but who are not ready for the complexity of complications with tube shunts. There is growing curiosity amongst all surgeons as to whether the Ex-Press will provide safety and success rates more reflective of trabeculectomy or of tube shunts.

The Ex-Press Mini Glaucoma Shunt.

Canal-based Surgeries

As for the canal-based surgeries such as the canaloplasty procedure developed by iScience International, the learning curve is a bit greater than the previously-mentioned procedures. That said, I believe that a gifted and motivated surgeon can master almost any procedure. However, this surgery is somewhat more complex and has steps that are not shared with trabeculectomy or tube shunts.

The technique needed to unroof Schlemm's canal requires a learning curve of at least dozens of cases just to achieve a base level of comfort.

Canaloplasty provides a full opening of Schlemm's canal.

In spite of this learning curve, I do believe that this surgery holds great promise in improving glaucoma outcomes and evolving away from bleb-related procedures. The migration away from bleb-related procedures is under way due to risks associated with thin avascular blebs, which include wound leaks and endophthalmitis.

Many prominent glaucoma specialists in the United States have had excellent success at mastering the procedure and helping their patients with advanced and complex glaucomas. I believe that continued momentum and dedication by glaucoma specialists and skilled general ophthalmic surgeons is warranted, based upon the initial body of work presented by the surgeons using the iTrack microcatheter from iScience Interventional. I believe that foregoing this procedure simply due to its complexity would be a long-term mistake and deprive glaucoma patients of an effective and innovative therapy.

With regard to procedures that seek to remove the inner wall of Schlemm's canal, such as the Trabectome, or to stent the inner wall of the canal with the Glaukos iStent, I believe we are at the forefront of a new era in glaucoma surgery. Particularly, the Trabectome procedure fathered by George Baerveldt, MD, warrants special appreciation and attention. I believe that the skill set needed and the accompanying learning curve make it an excellent procedure for both general ophthalmologists and glaucoma specialists alike.

The Trabectome seeks to unroof the inner wall of the canal. This is done in the anterior chamber with a handpiece that provides irrigation, aspiration and electro-cautery. The unique handpiece allows several clock-hours of the inner wall to be removed with the cautery device through a clear-corneal incision placed temporally. This wound is astigmatically neutral and similar in construction to the cataract wound. The fact the surgery is performed in the anterior chamber makes it an excellent option for facile cataract/ refractive and general ophthalmic surgeons.

The skills needed to perform this procedure can be acquired at a national course offered by Trabectome developer NeoMedix.

Opportunities Continue to Increase

In summary, I believe that although most general ophthalmologists have performed some number of trabeculectomies and at least a few tube shunts, the newer procedures offer another opportunity for surgeons to become comfortable with glaucoma procedures. The Alcon Ex-Press Mini Shunt, the iScience canaloplasty procedure and the Neomedix Trabectome offer interested surgeons an opportunity to become reacquainted with glaucoma procedures. Each has its own skill set and learning curve but all are reasonable procedures for a skilled and willing surgeon. OM

Andrew Rabinowitz, MD, is the glaucoma specialist at Barnet, Dulaney Perkins Eye Center, Phoenix, Ariz. His surgical techniques have been used in educational films demonstrating the appropriate usage of glaucoma shunts. He has no financial interest in any of the products mentioned in this article. Dr. Rabinowitz can be reached via e-mail at andrewrabinowitz@aol.com.