GLAUCOMA 56 EWAP MARCH 2022 it often takes years to develop an erosion, I’m not sure if I can say that definitively makes a difference.” Managing the complication If it’s in the early postop period, Dr. Razeghinejad said revision surgery is mandatory if the tube is exposed. If the patch is exposed and still covering the tube, topical antibiotics and lubricants (drops and gels) usually help with conjunctivalization of the patch, he said. With late tube exposure, Dr. Razeghinejad said the need for revision is urgent because the chance of endophthalmitis is high. The conjunctiva around the area of the tube exposure is usually friable and congested. “I do inject lidocaine plus epinephrine to balloon the conjunctiva and decrease the bleeding,” he said. “It also helps me to delineate the boundaries of free and scarred conjunctiva. I dissect the conjunctiva posteriorly, and due to the tissue expansion effect of the plate on the conjunctival tissue, there is enough conjunctiva over the plate to undermine and pull forward toward the limbus.” Generally, Dr. Razeghinejad said the conjunctiva at the area of tube exposures is not a good tissue to cover the new patch and tube, and it’s necessary to bring fresh conjunctiva from superior or the sides to close the defect area. He added that free conjunctival grafts or rotational flaps, double-layer amniotic membranes, and buccal membrane transplants may be used for superficial coverage in the event of conjunctival scarring.4,8 If the tube is inserted anteriorly (close to the limbus or at the limbus), Dr. Razeghinejad prefers to relocate it more posterior and close the original tube entry with Vicryl sutures. “When you close the tract, you have to over tighten the suture to stop the leak, which usually leads to astigmatism,” he said. “Vicryl sutures dissolve within 4–6 weeks, but nylon lasts longer and you have to deal with the astigmatism postoperatively if you use nylon sutures.” When you see the tube is exposed, whether it’s the plate or tube itself, Dr. Smith said it’s important to start antibiotics, manage the early infection if present, and seek the help of a retina specialist if indicated as in the case of endophthalmitis. The approach to an exposed tube also depends on what section of the tube is exposed, she said. If the plate is exposed, the whole tube usually has to come out because it’s hard to get the plate covered after the capsule is violated due to epithelialization within it. However, if it’s tube exposure over the tubing material, Dr. Smith said the approach is usually to go in and open the conjunctiva. “It’s important to cauterize any epithelial tissue that would have grown into and around the tube subconjunctivally.” Conjunctival closure may be a challenge in certain instances, so tissue mobilization, the use of amniotic membranes, conjunctival graft, or pedicle flap are ways of achieving adequate coverage.9 Dr. Smith said she tends to move the tube position as well because she thinks there is some mechanical effect that has a part to play in why the tube was exposed in that location. She usually moves the tube over about one clock hour toward 12 o’clock. Snaking and securing tube material during primary tube surgery as she directs the tube to the 12 o’clock position leaves extra tubing available for relocation of the entry point in the future if this is needed. Patch graft material or method is another discussion, she said. Whether you put a patch graft or create a long track for the tube as it enters the eye, as you revise, you should try to use patch material to cover the tube to prevent re-exposure. Most patients do well with tube revision. There are some extreme instances with severe infection or where the tube is completely expelled in which vision is significantly threatened, Dr. Smith said, but in most instances, patients recover fully following a revision with maintenance of pre-exposure IOP if it was just an exposed tubing. “When we think about exposed hardware in other parts of the body, often they remove that hardware,” Dr. Myers said. “In most cases, even those cases of infection, we don’t remove or replace the tube.” If tube position is good in the anterior chamber and on the sclera, and if it’s not too close to the limbus, the surgeon can patch over the tissue and 'ZposWre oH tWDinI OateriaN. Source (all): Oluwatosin Smith, MD
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