Eyeworld

82 | EYEWORLD | DECEMBER 2021 G UCOMA by Ellen Stodola Editorial Co-Director A tube shunt erosion or exposure is a complication that can occur often- times many years after surgery. Sev- eral experts discussed what to look for, why this complication occurs, and how to address it. Jonathan Myers, MD, noted there is about a 5–8% risk of a tube shunt erosion requiring a repair in the long run. 1 It's not rare, he said, but it's infrequent enough to be overlooked, espe- cially since it's often many years after surgery. The most concerning cases are the ones where infection ensued, and what's been most interesting is the vast majority of erosions don't involve infection, he said. "It's relatively uncom- mon to have a tube shunt-related infection," Dr. Myers said. "But usually when you do, there's an erosion." Most patients are asymptomatic or may have a little irritation under the eyelid. Some- times an erosion is small (half a millimeter), while other times it has clearly been eroding for months and is larger (3–5 mm or even more), Dr. Myers said. Dr. Myers noted that there are a couple of risk factors for tube shunt erosion. Patients with a Boston KPro (Massachusetts Eye and Ear) seem more at risk. "They have surface issues, are on chronic steroids, and often wear contact lenses," he said. "I do think it's more common to have an erosion in that setting." He noted a study by researchers at Duke University, 2 who published a series on tube shunts, indicating that patients with multiple anti-VEGF injections for macular degeneration and related issues were more likely to experi- ence tube shunt erosions. According to Oluwatosin Smith, MD, tube exposure is one of the more common compli- cations that can occur following tube shunt surgery. In the Tube Versus Trabeculectomy study, tube erosion occurred in 5% of patients in the tube shunt group with some of the patients having a recurrence. 3 "It can occur early on, which may be related to surgical technique, or further along after the patient has had the tube for many years," she said. The tube exposure can occur along the tube itself or along the plate of the drainage implant. Dr. Smith said some factors associated with tube erosion include location of the tube, posi- tioning, the point of entry into the eye, and a patient's history of other ocular surgeries or sys- temic disease. She also mentioned cases where the tube was exposed after trauma following a retina injection close to the tube. The possibil- ity of exposure should be kept in mind when implanting a tube. It's important to make sure the tube itself is covered by the eyelid at the pressure points and points where it enters the anterior chamber, she said. This is key, hence her tendency to enter the anterior chamber at 12 o'clock and at least 2 mm posterior to the limbus. Reza Razeghinejad, MD, said that tube exposure can be divided into two groups: early tube exposure and late-onset tube exposure. Early tube exposure, he said, is often caused by a dehiscence of the suture that se- cures the conjunctiva or conjunctival retraction and dehiscence due to having tension on the conjunctiva. The exact mechanism for late-onset tube exposures is not known, Dr. Razeghinejad said. It's likely related to an erosion of the overlying conjunctiva and patch graft due to the micro- movements of the tube with blinking and eye movements, he said. The reported risk factors for tube exposure are ocular inflammation, neovascular glaucoma, increased number of preoperative glaucoma medications, diabetes mellitus, prior ocular sur- geries with conjunctival violation (strabismus surgeries, retinal detachment surgeries, pteryg- ium surgery with free conjunctival flap, etc.), and inferiorly implanted tubes. 4–7 Late tube exposure is estimated to occur in 2.5–8.9% of patients and commonly more than 1 year postoperatively. 4–7 "As I work in a tertiary eyecare center, I get these patients every month," Dr. Razeghinejad said. "If you are in a private practice, you won't see as many as I see and manage." When tube exposure occurs, prompt surgical revision is highly recommended to prevent endophthalmitis, he added. Dr. Razeghinejad noted that he operated on a patient with a re-exposure who had intravit- real injection and tube revision by her surgeon About the physicians Jonathan Myers, MD Chief of the Glaucoma Service Wills Eye Hospital Philadelphia, Pennsylvania Reza Razeghinejad, MD Director Glaucoma Fellowship Program Wills Eye Hospital Philadelphia, Pennsylvania Oluwatosin Smith, MD Glaucoma Associates of Texas Dallas, Texas Tube shunt erosion/exposure COMPLICATED CASES

• Blank Page
• Blank Page (1)