The Trabectome (NeoMedix Corporation) permanently ablates a portion of the trabecular meshwork and inner wall of Schlemm canal to increase aqueous outflow (Figure 1). Several studies have shown that the procedure is an effective treatment with a favorable safety profile that reduces patients' IOP and need for glaucoma medication. It therefore may be offered earlier in the management of glaucoma than traditional filtering surgery and also as a combined procedure to patients with a visually significant cataract who need lower IOP and a lesser dependence on glaucoma medications.1-9 Because the mechanism of action is internal filtration and does not require a filtering bleb, ab interno trabeculotomy may avoid many of the vision-threatening complications of external filtration surgery such as trabeculectomy or aqueous tube shunts.10-15

INSTRUMENTATION

The Trabectome system consists of a single-use, bipolar instrument with irrigation and aspiration that is powered by a high-frequency electrosurgical generator and a peristaltic irrigation-aspiration console (Figure 2). The handpiece is a 19.5-gauge instrument with a tip that incorporates an insulated footplate that is pointed for insertion through the trabecular meshwork into Schlemm canal. The trabecular meshwork is vaporized and aspirated using high-frequency electrosurgical pulses to create an opening from the anterior chamber into Schlemm canal and the collector channels (Figure 3). Ab interno trabeculotomy has several other clinical advantages such as a temporal clear corneal approach, which leaves the conjunctiva available for subsequent conventional filtration surgery as necessary, a rate of infection and complications comparable with that of phacoemulsification, and the potential for combination with cataract extraction using the same temporal corneal incision (Figures 4 and 5).

INDICATIONS

The indications for ab interno trabeculotomy include variations of open-angle glaucoma: primary open-angle glaucoma, pseudoexfoliation, pigment dispersion, and uveitic and steroid-induced glaucoma. The procedure has also been performed for chronic angle-closure glaucoma with lysis of goniosynechiae and lens extraction. Patients who have early to moderate glaucomatous damage and IOP elevated above the target for the health of the optic nerve are good candidates for Trabectome treatment. Results from a previous retrospective study show that the procedure does not result in an IOP as low as trabeculectomy with antimetabolites. Ab interno trabeculotomy, therefore, is not suitable for patients with end-stage optic nerve damage who need very low IOPs.16

FOR SUCCESS

The selection of patients is critical to success. The ideal candidate has an open angle with a clear view of the angle structures, early to moderate glaucomatous damage, and a target IOP in the midteens. Although a higher preoperative IOP is desirable, those undergoing ab interno trabeculotomy combined with cataract surgery may have controlled IOP but a desire to reduce their reliance on medication. My colleagues and I have reported that ab interno trabeculotomy combined with cataract surgery lowers IOP and the number of medications required more effectively than cataract surgery alone.4,7,8

During surgery, it is imperative to properly identify the trabecular meshwork. Allowing blood to reflux into Schlemm canal by temporarily lowering the IOP is helpful when there is little pigmentation. If the landmarks are confusing, I recommend viewing the inferior angle and following the structures superiorly to the nasal angle. To avoid damage to the iris or cornea, I treat as much of the angle as is readily available, without forcing the probe too far laterally.

Postoperatively, I keep the patient on his or her glaucoma medications, especially aqueous suppressants, to prevent a spike in IOP. I prescribe pilocarpine 1% two to three times daily, tapering over 3 to 6 weeks in order to maintain the patency of Schlemm canal's opening. A steroid-induced rise in IOP is a distinct possibility, so I prescribe loteprednol 0.5% or start with prednisolone 1% but quickly switch to fluorometholone 0.1%. The IOP usually stabilizes by 1 to 3 months at a level that will persist over time.

CONCLUSION

Trabectome surgery is suitable for many patients with open-angle glaucoma. The procedure offers a favorable risk profile compared with traditional glaucoma filtering surgeries.16 Ab interno trabeculotomy increases aqueous outflow through the trabecular outflow pathway, lowering IOP to the normal physiologic level (the midteens) regardless of preoperative IOP.1-3,9

Compared to other microinvasive glaucoma surgeries, ab interno trabeculotomy opens a wider area of Schlemm canal without the presence of a permanent foreign body. The procedure also spares the conjunctiva due to the internal approach to the angle.

Ab interno trabeculotomy is easily combined with clear corneal phacoemulsification. Unlike trabeculectomy, the success of Trabectome surgery seems to be enhanced by concurrent phacoemulsification cataract extraction. Patients with advanced or sight-threatening glaucoma who require a very low target IOP may be better suited to standard trabeculectomy, but ab interno trabeculotomy is especially useful for those in whom trabeculectomy is high risk or individuals who have an ocular surface that is incompatible with filtration bleb surgery.

Brian A. Francis, MD, MS, is the Riffenburgh professor and director of glaucoma as well as associate professor of ophthalmology at the Doheny Eye Institute, Keck School of Medicine, University of California, Los Angeles. He is a paid consultant to NeoMedix Corporation. Dr. Francis may be reached at (323) 442-6454; bfrancis@usc.edu.

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  2. Minckler D, Baerveldt G, Ramirez MA, et al. Clinical results with the Trabectome, a novel surgical device for treatment of open-angle glaucoma. Trans Am Ophthalmol Soc. 2006:104:40-50.
  3. Minckler D, Mosaed S, Dustin L, Francis B, and the Trabectome Study Group. Trabectome (trabeculectomyinternal approach): additional experience and extended follow-up. Trans Am Ophthalmol Soc. 2008;106:149-160.
  4. Francis BA, Minckler D, Dustin L, et al; Trabectome Study Group. Combined cataract extraction and trabeculotomy by the internal approach for coexisting cataract and open- angle glaucoma: initial results. J Cataract Refract Surg. 2008;34(7):1096-1103.
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