What is the Trabectome?
Chat Highlights
February 7, 2007

On Wednesday, February 7, 2007, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "What is the Trabectome?"

Moderator:  Welcome, Dr. Wilson.

Dr. Rick Wilson: Thank you.

Moderator:  We would like to have more information about trabectome. For example, what advantages does it offer that are not offered by trabeculectomy and aqueous shunts?

[Editor’s note: The instrument (Trabectome) and the procedure (trabectome) are three-syllable words (Tra-bec-tome).]

Dr. Rick Wilson: Although trabeculectomy and aqueous shunts are effective, they have serious side effects. Therefore; we are always looking for less invasive surgery. Since most of the decrease in outflow in chronic open-angle glaucoma seems to be at the level of the trabecular meshwork, procedures aimed at eliminating that resistance offer promise.

We can bridge over the trabecular meshwork with small tubes that then fit into Schlemm's canal. We can remove the trabecular meshwork for part of the circumference of the inside of the eye, or we can try to decrease the resistance of the trabecular meshwork by stretching it into the eye.

Moderator:  Is a piece of the trabecular meshwork removed during a trabectome?

Dr. Rick Wilson: The Trabectome removes about two or three hours of circumference of the trabecular meshwork, supposedly without harming Schlemm’s canal or the collector channels that carry aqueous to the surface of the eye and the waiting aqueous veins.

P: Why did you say "supposedly without harming" other structures? Is that not known?

Dr. Rick Wilson: Because the complications of a trabectome procedure are far fewer than for a trabeculectomy, we hope that the trabectome procedure will prove applicable to patients earlier in the course of glaucoma, that is, those patients with less severe glaucoma who have trouble with medicine or would like to be on less or no medicine. The light microscopy of animals and eye-bank eyes that have had the procedure have not shown noticeable damage to the outside wall of Schlemm's canal and collector channels. What is happening on a cellular level is not completely known.

P: Is the Trabectome used only at teaching institutions?

Dr. Rick Wilson: Its use started at the University of California, Irving, and is now just branching out from a handful of teaching centers to a much larger group of institutions.

P: When I asked a glaucoma specialist about trabectome, he said, "It's new, and I doubt it will amount to anything." Are there some drawbacks?

Dr. Rick Wilson: It is new and much remains to be learned about it. However, as one of four new minimally invasive procedures, trabectome seems to me to offer the most promise.

P: I like the mechanical nature of trabectome, but how do you control the amount or rate of outflow? Isn’t it kind of like removing the stopper from the sink?

Dr. Rick Wilson: It would be if the pipe on the other side of the trabecular meshwork were too large. However the collector channels are small and drain into veins so the eye pressure is never less than venous pressure, around 9 mm HG. Therefore, one advantage of this surgery, besides being quick and minimally invasive, is that too-low intraocular pressures are never a problem.

P: Do you perform this procedure?

Dr. Rick Wilson: I was recently forced into retirement because of a back injury when I was 17- years old that has become unbearable when I operate. Before retirement, I was the only surgeon outside of California doing the procedure.

P: Did you find transferring your skill from performing a trabeculectomy to a trabectome difficult or relatively easy?

Dr. Rick Wilson: Those two are entirely different procedures. What helped me was the many goniotomies that I have done on babies. Trabectome is a similar procedure.

P: How does trabectome differ from goniotomy?

Dr. Rick Wilson: A goniotomy is done with a tiny sharp knife that incises into the trabecular meshwork and any abnormal tissue over it, thereby returning the outflow to normal. The trabectome uses electrocautery across a tiny hook that is placed in Schlemm's canal to vaporize the trabecular meshwork.

P: Can a patient who has already had a trabeculectomy have a trabectome?

Dr. Rick Wilson: It will probably not be as successful because scarring of Schlemm’s canal occurs at the site of the trabeculectomy. The scarring may limit flow and probably decreases outflow after a trabectome.

Moderator:  What about the other way around? Can a patient who has had a trabectome have a trabeculectomy?

Dr. Rick Wilson: Yes. Because trabectome is a minimally invasive procedure, it should not affect the success of either filtration (trabeculectomy) or shunt surgery.

P: What factors will a physician consider in deciding on a trabectome or trabeculectomy for a patient?

Dr. Rick Wilson: Trabectome seems to work best on people who have not had previous surgery or inflammation. Since the resultant intraocular pressures are in the mid- or high-normal range, patients who require low-normal or below-normal pressures are not well suited for the procedure.

P: Is the amount of trabecular meshwork removed by the Trabectome at the discretion of the surgeon, or is the same amount always removed?

Dr. Rick Wilson: The surgeon can either have one entrance wound in the peripheral cornea and remove two to four clock-hours of trabecular meshwork or two such wounds 180 degrees apart, doubling the amount of removal.

P: What is the ideal angle and why is it important?

Dr. Rick Wilson: We don't know for sure how much of the trabecular meshwork would be optimal to remove. Two to three clock-hours has worked adequately in most of the operations performed. Different amounts of circumference removal are being tried, and we hope this question can be answered soon. I will be at the American Glaucoma Society meeting at the beginning of next month and may be able to tell you more after the talks there.

P: What is the failure rate and rate of infection of trabectome?

Dr. Rick Wilson: I have not heard of any infections. The failure rate has been between 20 and 40%, depending upon which center is reporting and the degree of difficulty of the cases they are trying. Most patients who are a success remain on one glaucoma drop or more, but were uncontrolled before surgery.

P: What IOP goals can be achieved with trabectome?

Dr. Rick Wilson: Target pressure varies for each individual. IOP goals that can be achieved with this surgery are in the middle to upper teens.

P: How many trabectomes can be done on one eye?

Dr. Rick Wilson: If only one incision is made each time, then four. If two incisions are made each time, then two.

P: Since a trabectome creates no filtering bleb, and since no antimetabolites (mitomycin-C) are used, are complications fewer than with a trabeculectomy?

Dr. Rick Wilson: There is usually a small amount of bleeding into the eye with a trabectome, but the blood is usually gone within a day or two. I really haven't seen any lasting complications.

P: Does the patient’s age affect the success rate of trabectome?

Dr. Rick Wilson: Normally, older patients do better with trabeculectomy, but that may not be the case with trabectome.

Moderator:  Dr. Rick, thank you for providing more information about this interesting new glaucoma procedure.

Dr. Rick Wilson: You’re welcome. Everyone have a good two weeks. Good night and good luck.

[Editor’s note: Dr. Wilson first told us about the Trabectome during the chat, “Glaucoma, What’s New,” on December 6, 2006.]

On February 21, Dr. Wilson discussed "Common Mistakes Patients Make" in the Chat room. Click here for highlights of that meeting.

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