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Smaller sutures may reduce number of aqueous shunt exposures
Study examines factors associated with failed revision of shunt exposure.
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Patients who receive aqueous shunts may benefit from small sutures to avoid device exposure, according to a physician.
In addition, vigilant postoperative examinations are important to identify conjunctival erosions, which require revision.
“Aqueous shunts play an important role in the surgical management of glaucoma. As with any implant, mechanical complications may occur years after implantation. Unfortunately, sometimes more than one surgical revision is necessary,” study co-author Nicholas P. Bell, MD, said in an interview with Ocular Surgery News.
The study
In a retrospective case study, published in the Journal of Glaucoma, 43 eyes of 43 patients with anterior chamber or pars plana aqueous shunts who underwent surgical revision for device exposure were evaluated. All of the tubes were covered with a patch graft. The average time from aqueous shunt implantation to the initial conjunctival erosion was 21.5 months. Thirty-three eyes experienced tube exposure, seven eyes experienced plate exposure, and three eyes experienced other complications. In three eyes, the aqueous shunt was explanted.
The remaining 40 eyes were followed after repair of the initial exposure, and 17 (43%) needed additional surgical intervention. Fifteen eyes (45%) were from the tube exposure group, and two eyes (29%) were from the plate exposure group. The average time until the second revision was 78 months.
Patients with diabetes had a three times higher risk of failed revision than patients without diabetes (P = .028). Diabetes was also associated with a shorter interval between the initial repair and another extrusion.
“We know that diabetics don’t heal well, and the conjunctiva is not healthy in a proliferative diabetic,” Bell said. “We also know that long-term use of glaucoma medications can toxify the conjunctiva over the years.”
Failed revisions were also associated with black race (P < .0001), pre-shunt glaucoma medications (P = .0085), previous glaucoma laser surgery (P = .0081) and combined initial shunt implant surgery (P = .0289).
IOP, number of medications and visual acuity remained stable after the initial revision surgery.
Sutures
Sutures may play a role in aqueous shunt exposure.
Seventeen of 18 suture exposures occurred in eyes in which 5-0 polyethylene terephthalate sutures were used to secure the plate to the sclera.
“We noticed a drastic decrease in the amount of exposures when we switched from the large, braided 5-0 Mersilene suture to the smaller, less bulky 8-0 nylon suture for the initial aqueous shunt implantation surgery. The 5-0 Mersilene knots were too large to rotate into the holes of the plate. Normal wear and tear from eyelid blinking over those knots probably eroded the conjunctiva,” Bell said.
He said there have not been any problems with keeping the plate attached to the sclera since switching to 8-0 nylon sutures to anchor the plate.
Physicians should pay close attention postoperatively to the conjunctiva overlying aqueous shunt plates and tubes, especially in patients with risk factors, to make sure there is no thinning or development of an exposure, Bell said. Furthermore, he recommended that if the device appears infected, it may need to be explanted.
In addition, tension on the fragile overlying conjunctiva should be minimized during repair of the exposure. If it is pulled too tightly, it may be more likely to re-expose later, he said.
“A constant struggle in the management of glaucoma is keeping the disease from progressing while trying to limit the collateral damage created by our medical and surgical interventions,” Bell said. – by Cheryl DiPietro and Matt Hasson