Instrument allows novel approach to ab interno trabeculotomy

Glaucoma surgery with the Trab360 does not require an implant or external power source.

Issue: July 10, 2015

BySavak Sev Teymoorian, MD, MBA

The evolution of technology in microincision glaucoma surgery pushes ophthalmologists and developers to create new approaches to better control IOP. If we were to imagine the ideal glaucoma surgery, what would it include?

The ideal surgery

The first issue is to decide between an ab interno vs. ab externo approach. When treating glaucoma patients, the gold standard remains trabeculectomy and tube shunt surgery. This means that any new procedure that spares conjunctival tissue for use in later glaucoma surgery is ideal. Therefore, an ab interno approach is ideal.

The next question is whether or not to use an implant. One of the major problems, even with gold standard surgeries, is that the anatomy is significantly altered away from its natural state. The further away any procedure gets from maintaining the normal ocular architecture, the more risk of complications. The placement of implants, such as the ExPress glaucoma filtration device (Alcon) or tube shunts, adds complicating factors, including how the eye interacts with the device. It also raises possible complications such as migration and erosion. Therefore, when given the option of using or avoiding implants, the better option appears to be a procedure that is implant independent.

Another issue to contemplate is whether the surgical intervention needs to have a power source or not. Surgical procedures such as Trabectome (NeoMedix) and gonioscopy-assisted transluminal trabeculotomy (GATT) depend on having an external source of power. The Trabectome uses electrocautery, and GATT can involve an illuminated microcatheter. This requirement adds hurdles that must be cleared for a successful procedure. The ideal procedure would not depend on an external source and thus would be manpowered.

The last area to address is whether to perform the ideal procedure with or without other interventions, including cataract surgery. Because patients and their presentations are so diverse, including their phakic state, the best option would be one that gives the surgeon the option to perform it with or without other interventions.

Trab360

Figure 1. Obtain a clear view of the angular structures through the use of a gonioprism while both rotating the patient’s head away and tilting the microscope.

Figure 3. Unroof the canal by removing the handpiece.

Figure 4. The opposing side of the canal can then be unroofed in a similar fashion if desired by orienting the tip of the handpiece 180° from the initial application, allowing this procedure to be adjustable to the length of canal the surgeon wishes to open.

With these in mind, the ideal surgery would be an ab interno, implant-less, manpowered intervention that can be done independently or with other procedures. The use of the Trab360 instrument from Sight Sciences allows this to be accomplished by performing an ab interno trabeculotomy. The procedure is performed as follows:

1. Create a small-length clear corneal incision similar to one used for cataract surgery (or use the same incision if performed in conjunction with cataract extraction).

2. Obtain a clear view of the angular structures through the use of a gonioprism while both rotating the patient’s head away and tilting the microscope (Figure 1).

3. Advance the tip of the Trab360 instrument to the trabecular meshwork and penetrate past the trabecular meshwork and the inner wall of Schlemm’s canal (Figure 2).

4. Extend the medical grade polymer up to 20 mm through Schlemm’s canal by rotating the wheel on the handpiece.

5. Unroof the canal by removing the handpiece (Figure 3).

6. Retract the polymer back to the handpiece by rotating the wheel in the opposite direction.

The opposing side of the canal can then be unroofed in a similar fashion if desired by orienting the tip of the handpiece 180° from the initial application, allowing this procedure to be adjustable to the length of canal the surgeon wishes to open (Figure 4).

The ability to perform an adjustable ab interno trabeculotomy that does not require an external power source or implant provides a treatment option with ideal parameters. It can be incorporated with cataract surgery or done as a stand-alone procedure, depending on the patient’s needs.

For more information:
Savak Teymoorian, MD, MBA, can be reached at Harvard Eye Associates, 24401 Calle De La Louisa, Suite 300, Laguna Hills, CA 92653; email: steymoorian@harvardeye.com.

Disclosure: Teymoorian reports he is a consultant/adviser to Aerie, Allergan, Glaukos and MDbackline.com, receives grant support from Bausch + Lomb, and receives lecture fees from Vindico.