Ab interno approach affords atraumatic technique for glaucoma shunt removal

TAKE HOME:

If explantation of a miniature stainless steel glaucoma shunt becomes indicated, an ab interno technique offers several advantages compared with the traditional external approach.

Dr. Grover

By Cheryl Guttman Krader; Reviewed by Davinder S. Grover, MD, MPH

Dallas-A gonioprism-assisted ab interno approach for explantation of the miniature stainless steel glaucoma shunt (Ex-PRESS, Alcon Laboratories) is an efficient and minimally invasive technique with an advantage of sparing the conjunctiva, according to its innovators (Davinder S. Grover, MD, MPH, and Ronald L. Fellman, MD).

Its use in two patients-one with severe eye pain secondary to a malpositioned shunt and the other with a non-functioning device-was described in a recently published paper [JAMA Ophthalmol. 2013;131:1356-1358]. The authors believe the explantation technique is worth knowing about considering the growing popularity of the miniature shunt in the care of patients with glaucoma.

“Use of the [shunt] has been increasing among some surgeons who feel it provides a more predictable outcome with faster visual recovery and potentially a lower risk of hypotony compared [with] trabeculectomy,” said Davinder S. Grover, MD, MPH, lead author of the paper and a glaucoma specialist, Glaucoma Associates of Texas, Dallas.

Additionally, the device has been associated with a low risk of erosion, he noted.

“Nevertheless, as the [shunt] is used in more and more eyes, it is likely that glaucoma surgeons will be seeing more patients with device-related complications in the future,” Dr. Grover said.

The traditional external approach to removing the shunt involves both conjunctival and scleral flap dissection. With an external approach, the surgeons may encounter difficulties with closure because of the poor quality scleral and/or conjunctival tissue. The latter situation is avoided entirely using the ab interno approach, which is much less traumatic and invasive overall, he explained.

Two patient cases

The first patient in which the ab interno technique was used had undergone bilateral implantation of the miniature shunt performed at another practice. She reported developing pain in the right eye on the day after the procedure. She presented 6 months later to Glaucoma Associates of Texas with severe pain. Examination revealed a healthy bleb, but on gonioscopy it was seen that the internal tip of the shunt was embedded in the iris.

Surgical intervention became indicated when medical management aiming to reduce inflammation and pain was not successful.

“We hated to disrupt the conjunctiva because the glaucoma surgery looked beautiful, and that is why we undertook an ab interno approach to remove the malpositioned shunt,” Dr. Grover said. “At the same time, in order to protect against bleb failure, we enlarged the internal sclerostomy.

“The patient experienced immediate resolution of her pain, and with the ab interno conversion to a traditional filtering procedure, her IOP remains well controlled after 1.5 years of follow-up,” he said.

The second case described in the paper involved removal of the shunt in a patient who developed a tenon cyst that was refractory to bleb needling with mitomycin C. An ab interno circumferential trabeculotomy was also performed at the time of shunt removal.

“Given the ease and safety of the ab interno approach for shunt removal, we believe it is in the best long-term interest of any patient to remove the shunt if it no longer serves a purpose,” Dr. Grover said.

“We are not advocating taking a patient to the operating room primarily to remove the shunt,” he said. “However, if an eye with [this] shunt requires an additional surgical procedure, we feel it would be prudent to remove the shunt to protect against the low risk of subsequent erosion and exposure.”

Performing the procedure

The ab interno procedure involves creation of two corneal paracenteses made approximately 4 clock hours nasally and temporally from the shunt.

After filling the anterior chamber with viscoelastic and using a gonioprism to visualize the shunt within the angle, a 25-gauge microvitreoretinal blade is introduced through the corneal incisions to dissect the scleral tissue adjacent to the shunt and then to cannulate its distal lumen.

The device is then delivered into the anterior chamber, and using a microsurgical forceps for control, it is explanted through an enlarged temporal corneal incision.

Davinder S. Grover, MD, MPH

E: dgrover@glaucomaassociates.com

Drs. Grover and Fellman have no relevant financial conflicts of interest pertaining to this subject.