Combined Phacoemulsification and Trabectome
The current standard for surgical treatment of glaucoma remains trabeculectomy ab externo. Although an excellent procedure, the potential for intraoperative, perioperative, and long-term complications and side effects has led to the search for safer and less invasive filtration proce-dures. One of these, trabeculectomy ab interno, also known as Trabectome (NeoMedix Corp, Tustin, California), was approved for clinical use in the United States in 2004.
Using thermal energy similar to bipolar cautery, the Trabectome removes a strip of the trabecular meshwork and the inner wall of Schlemm’s canal for 60 to 140 degrees in the nasal angle, thus providing a direct com-munication between the anterior chamber and collecting channel. Recent studies regarding the intraocular pressure (IOP)-lowering effect of cataract surgery alone have led glaucoma surgeons to include this surgery in their treatment algorithms as well. This chapter focuses on the technique of combined phacoemusification and ab interno trabeculectomy (Trabectome) and briefly presents initial clinical data for this technique.
The Trabectome utilizes gravity-driven infusion and automated aspiration. The handpiece consists of a 19.5-gauge infusion sleeve handle, a 25-gauge aspiration port, and coupling for the ablation unit at the tip. The 25-gauge shaft is 5 mm longer than the infusion sleeve and this distal end terminates in a footplate (Figure 16-1). This footplate facilitates penetration into Schlemm’s canal and insulating material over its surface helps protect the canal’s outer wall. The meridional diameter of the footplate varies between 350 and 500 µm.
Basic Surgical Technique
The typical preoperative dilating, nonsteroidal anti-inflammatory, and antibiotic regimen for cataract surgery is used. Sitting temporally, the surgeon rotates the patient’s head away from himself or herself, and the microscope is rotated towards the surgeon approximately 30 to 45 degrees, giving a direct gonioscopic view of the nasal angle. The microscope is at an approximate 45-degree angle and combined with the tilt is approximately 70 to 80 degrees from the eye in primary gaze. The Trabectome procedure may be done before or after cataract extraction according to surgeon’s preference.
A 1.7-mm keratome blade is used to create a beveled temporal corneal incision if done prior to cataract extraction and there is a desire to leverage a smaller incision than is typical for the cataract procedure. If done post cataract extraction, the standard clear cornea temporal incision used for phacoemulsification may be utilized without limitations. Hydroxypropyl methylcellulose 2% (OcuCoat) is then injected into the anterior chamber. The Trabectome handpiece is inserted and advanced to the nasal angle through the anterior chamber with the infusion on. Through direct visualization, using a Trabectome goniosurgical lens (a modified Swan-Jacobs lens), the pointed tip of the footplate is then inserted through the trabecular meshwork and into Schlemm’s canal. After seated appropriately, the footswitch is activated to the cautery position and the surgeon advances the handpiece for approximately 90 to 110 degrees of treatment. Some advocate initially starting in a clockwise fashion for the first portion of ablation then re-engaging the canal and completing the treatment counterclockwise. We prefer a single treatment pass. The initial power setting that we advocate is 0.9 W, although others have suggested 0.7 to 0.8 W. The power should be titrated depending on the desire to ablate a wider strip of trabecular mesh-work or to minimize the treatment’s effects.
The postoperative drop regimen consists of an antibiotic 4 times daily for 1 week and a topical steroid 4 times daily tapered over 3 to 4 weeks. Topical glaucoma drops are resumed as needed.
Results from a retrospective review of 1127 Trabectome procedures (738 Trabectome-only and 366 Trabectome-phacoemusification surgeries) show a reduction of IOP in Trabectome-phacoemusification of 18% (20.0 ± 6.2 mm Hg to 15.9 ± 3.3 mm Hg) at 12 months, with a 40% reduction (25.7 ± 7.7 mm Hg to 16.6 ± 4.0 mm Hg) for Trabectome alone at 24 months. The most common complication was intraoperative reflux bleeding (77.6%). No cases of wound leak, sustained hypotony, choroidal hemorrhage, or decrease of visual acuity (more than 2 lines) were noted in this series. Another recent prospective case series (304 consecutive eyes) analyzing combined cataract extraction and Trabectome reported similar results in both IOP lowering (20.0 ± 6.3 mm Hg to 15.5 ± 2.9 mm Hg) at 1 year, as well as safety profile.
Combined phacoemulsification and ab interno trabeculectomy (Trabectome) has good initial results. This technique offers the ability to lower IOP without precluding the ability of future traditional incisional glaucoma surgeries by sparing the conjunctiva. In addition, due to its minimally invasive nature, Trabectome has a good safety profile with low risk of endophthalmitis, hypotony, vision loss, and choroidal hemorrhage as compared with trabeculectomy ab externo.
- Trabectome lowers IOP while maintaining the ability to perform future incisional glaucoma procedures by sparing the conjunctiva.
- Trabectome has a good safety profile compared with trabeculectomy ab externo.
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