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New glaucoma surgery increases aqueous outflow
The procedure can be performed alone or in combination with cataract surgery.
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Today there are a number of new and exciting surgical procedures available to our glaucoma patients, and these new surgical instruments and techniques are being rapidly adapted by ophthalmic surgeons worldwide.
IOP in glaucoma patients can be lowered either by decreasing the production of aqueous or increasing its outflow. The trabecular meshwork is the anatomic location of the greatest resistance to aqueous outflow. The newest surgical device to address the outflow mechanism using a minimally invasive approach is the Trabectome surgical system (NeoMedix, Tustin, Calif.).
The procedure
The Trabectome instrument forms a trabeculotomy using an internal approach. It consists of a disposable hand piece of 19.5-gauge instrument with a tip that incorporates an insulated footplate pointed for ease of insertion through the trabecular meshwork into Schlemm’s canal. The trabecular meshwork and inner wall of Schlemm’s canal are selectively vaporized and aspirated using high-frequency bursts of electrocautery heat energy. A strip of 90 degrees to 120 degrees of tissue is usually removed using one surgical incision.
 The insulated tip of the Trabectome hand piece eases insertion through the trabecular meshwork into Schlemm’s canal.  The trabecular meshwork and inner wall of Schlemm’s canal are selectively vaporized and aspirated using high-frequency bursts of electrocautery heat energy. Images: NeoMedix |
The removal of more than 120 degrees of tissue requires two surgical incisions. The instrument also has an aspiration port located adjacent to the bipolar electrode and delivers continuous irrigation, so the anterior chamber remains formed during the surgery and excess heat energy is dissipated.
Because the trabecular meshwork itself and the inner wall of Schlemm’s canal are physically opened and removed, a direct communication is formed between the collecting channels and the anterior chamber. This essentially bypasses a sector of aqueous outflow resistance. Also, this procedure does not create a subconjunctival bleb as routinely found in the standard trabeculectomy surgery. The power settings can be adjusted based on intraoperative responses judged by the surgeon.
Standalone or combination procedure
Another unique aspect of this procedure is that it can be performed as a standalone surgery or in combination with cataract surgery. Prior to the surgery, antibiotic and nonsteroidal anti-inflammatory drops are instilled in the operative eye. In the standalone surgery, 1% or 2% pilocarpine is administered to bring about pupillary miosis for easier instrument access into the chamber angle.
In combined surgery cases the pupil is dilated and the surgeon has the option to either perform the Trabectome procedure first, followed by the cataract surgery or the Trabectome procedure can be done after the cataract has been removed and an intraocular lens implanted.
 A strip of 90 degrees to 120 degrees of tissue is usually removed using one surgical incision. |
 Because the trabecular meshwork itself and the inner wall of Schlemm’s canal are physically opened and removed, a direct communication is formed between the collecting channels and the anterior chamber. |
The surgical incision is closed with a suture, and the patient is placed on routine postoperative topical medications and 1% pilocarpine three or four times a day for at least 1 month. The pilocarpine helps keep the iris tissue out of the angle and minimizes contraction of the surgical opening and scar tissue formation.
Postsurgical expectations
It is not unusual to see a transient hyphema and mildly elevated IOP on the first postoperative day. Bleeding at the surgical site occurs routinely during the removal of tissue with this procedure and accounts for the postoperative hyphema.
The success rate with Trabectome surgery has been found to be comparable to both trabeculectomy and glaucoma drainage implant (tube shunt) surgery. Unlike these more invasive filtering surgeries, Trabectome surgery has been found to have a favorable safety and risk profile with relatively minimal postsurgical complications. Overall, there is a lesser chance of postoperative cataract than with other filtration surgeries unless there is inadvertent damage to the lens during the procedure.
Hypotony is essentially nonexistent; the range of expected postoperative IOP is usually in the mid teens. This procedure may also be a useful option to perform even in the setting of well-controlled glaucoma as an attempt to reduce topical medication use and improve patient compliance.
- Leonid Skorin Jr., OD, DO, FAAO, FAOCO, a Primary Care Optometry News Editorial Board member, practices in Albert Lea, Minn., and writes and lectures on ocular disease and neuro-ophthalmic disorders. He underwent fellowship training in neuro-ophthalmology. He may be contacted at the Albert Lea Medical Center, Mayo Health System, 404 West Fountain St., Albert Lea, MN 56007; (507) 373-8214; skorin.leonid@mayo.edu.
- Disclosure: Dr. Skorin has no direct financial interest in the products mentioned in this article nor is he a paid consultant for any companies mentioned.