Trabectome

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Author: Thanh-Thao Vu
Published:
Specialties: Ophthalmology
Schools: Gavin Herbert Eye Institute, University of California Irvine
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This is a trabectome procedure performed on a patient with moderate severity open angle glaucoma. Trabectome is a minimally invasive glaucoma surgery (MIGS) developed by Baerdveldt and Chuck where the trabecular meshwork is electrocauterized, irrigated, and aspirated under gonioscopy to improve the drainage of aqueous humor and reduce intraocular pressures.

Procedure
Topical TetraVisc is first administered to the eye. The patient’s head is rotated 30 degrees away from the surgeon and the microscope tilted 30 degrees toward the surgeon. The patient’s axial core can be rotated if turning the neck proves difficult. The gonioscope lens is used to visualize the trabecular meshwork, the pigmented line between Schwalbe’s line and the scleral spur. A 1.7 mm temporal clear corneal and uniplanar incision is made 2 mm anterior to the limbus.

While applying continuous irrigation to deepen the angle, the Trabectome handpiece is introduced into the anterior chamber under gonioscopic visualization, and the end of the device was inserted into the inferonasal trabecular meshwork. When properly inserted, the trabecular meshwork should enter between the electrode tip and the footplate, causing the footplate to be obscured by the trabecular meshwork. The handpiece is used to ablate trabecular meshwork at a setting of flow 3 and 0.7 mW. It is rotated superiorly to create a 120 degree cleft, exposing the outer white wall of Schlemm’s canal. Care must be taken to prevent outward push on Schlemm’s canal by applying a slight inward pull during ablation. The handpiece may need to be readjusted as it is rotated in a counter-clockwise fashion.

The handpiece is removed from the anterior chamber. The patient’s head is returned to a neutral position, and BSS was used to exchange viscoelastic from the anterior chamber through the temporal wound. BSS is to irrigate red blood cells from the Schlemm’s canal collector channels. The gonioscope is used to verify the cleft. At the conclusion of the case, the intraocular chamber is formed and pressure checked to be appropriate via digital palpation.

Indications
Trabectome is indicated for narrow-angle [1], open-angle, and secondary glaucoma with uncontrolled intraocular pressures and progressive nerve injury refractory to maximal or tolerable medication management [2]. As a MIGS, trabecome can be considered in initial stages of glaucoma due to its safety and quick routine recovery. Reduction of drops due to side effects, costs, or poor compliance are reasons to offer this procedure to patients [3]. Trabectome surgery can also be performed in conjunction with cataract surgery, in pseudophakic and phakic eyes, and after trauma, scleral buckle [4], laser trabeculoplasty [5], or failed trabeculectomy or tube shunt [6,7].

Contraindications
Contraindications are few but the most common is pathology that limits gonioscopic view of the angle (active neovascular glaucoma, uveitis, corneal edema etc).

Setup
Patient’s head is rotated 30 degrees away from the surgeon and the microscope rotated 30 degrees toward the surgeon to provide optimal surgical approach.

Preoperative Workup
The patient’s glaucoma stage and type are identified. History taking should involve asking patients about trauma and prior eye surgeries. A complete ophthalmic examination is performed, including intraocular pressure and assessment of the angles under gonioscopy. Nerve OCTs and Humphrey visual fields are also obtained. No bloodwork, EKG, or imaging are required. Anesthesia questionnaire is completed prior to the procedure.

Anatomy and Landmark
Trabecular meshwork should be identified as the pigmented line between Schwalbe’s line and the scleral spur. Care must be taken to not ablate the ciliary body band. Blood reflux from Schelmm’s canal collector channels to confirm the ablation target can be induced by burping the main incision. After ablation, the cleft should be verified. The pigmented line from the trabecular meshwork should no longer be visible and only the outer wall of Schlemm’s canal seen.

Advantages/Disadvantages
Numerous studies have looked at the efficacy of trabectome surgery. Intraocular pressure drops to the mid-teens and decreasing the number of medications in most cases [8]. Unlike trabeculectomy or tube shunts, there is little scarring, the conjunctiva is preserved, the recovery is predictable, and there are less complications [3]. Patients with higher IOPs stand to benefit with greater reductions in IOPs than those with lower IOPs. There is limited data on the long-term success rate of trabectome surgeries. Studies following patients after surgery show that trabectome alone has a 70% success rate at 1 year but only 22% at 2 years [9,10,11].

Complications/Risks
The most common complications are transient hyphema, peripheral anterior synechiae, corneal injury, and transient IOP spikes of 10 mmHg or higher. Surgical failure can be due to incomplete or improper removal of the trabecular meshwork as well as damage to the ciliary body band or surrounding tissues [12]. The rate of serious vision-threatening complications, such as hypotony, cyclodialysis cleft, choroidal hemorrhage, and endophthalmitis, is <1% [13].

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