37 EyeWorld Asia Pacific | June 2024 Dr. Weng also mentioned that there are certain indications for glaucoma surgery, such as neovascular glaucoma, where intravitreal injections may actually improve procedural success.7 “Because steroids and anti-VEGF suppress inflammation and neovascularization, their effects on patient pathology and perioperative fibrosis could theoretically be beneficial, although this remains unproven,” she said. Finally, she noted concerns with the actual injection procedure. “I typically avoid giving intravitreal injections within the first few days following a glaucoma surgery,” she said. It is also important to avoid injecting through involved areas such as a tube shunt plate or the bleb as this could result in erosion and ultimately failure.8 Dr. Schehlein added that anti-VEGF injections have been linked to higher rates of recurrent glaucoma tube erosions in patients with age-related macular degeneration (AMD).9 She agrees that it is critical to inject the medication away from the tube shunt or trabeculectomy and take care with inserting and removing the eyelid speculum. “All patients, but especially glaucoma patients with a history of incisional surgery, should be instructed not to touch or rub their eye following an injection.” She noted that other studies suggest that higher postoperative IVIs in incisional glaucoma surgery may improve outcomes. “A study by Chang et al. found that >7 IVIs after traditional glaucoma surgery was associated with improved success (IOP reduction ≥20% with 5<IOP≤ 21 mm Hg). All patients had received at least 1 IVI prior to their glaucoma surgery,” she said. “The authors noted that the group who received postoperative IVIs had more diabetic retinopathy and retinal vascular occlusions, but both groups had similar rates of NVG (where IVIs have a therapeutic effect).”7 The effect of intravitreal injections on the success of MIGS is not well studied, Dr. Schehlein added. However, MIGS procedures can be used to treat persistent IOP elevation related to intravitreal injections. “I would also note that glaucoma patients tend to have significant ocular irritation and ocular surface issues if they are taking topical medications,” she said. “The betadine prep used during IVI may further irritate the ocular surface, however, it is unlikely that this would affect any pre-existing glaucoma surgeries done on the eye.” In terms of whether intravitreal injections cause glaucoma to progress more quickly, Dr. Weng said the jury is still out. “There have been some studies suggesting that recurrent intravitreal injections may hasten progression of mean deviation,” she said. But she added that these studies are often smaller, retrospective analyses that may have confounding factors.10,11 “While we work to discern whether or not a true association exists, it is important to monitor IOP closely in all patients receiving injections, especially in those with glaucoma or a susceptibility to glaucoma,” she said. Dr. Schehlein agreed that this is an area of active research and pointed out several studies which have shown that the total number of injections is associated with an increased risk of elevated IOP, possibly due to decreased outflow facility, the exact mechanism of which is currently unknown and is likely multifactorial.12,13 A study from Eadie et al. found that 7 or more injections of Bevacizumab were associated with a higher annual risk of glaucoma surgery.6 “It is possible that the frequency of injections impacts the need for glaucoma procedures, however, the data is minimal,” she said. “One study found that almost 9% of patients undergoing treat and extend with Aflibercept and Ranibizumab had a sustained intraocular pressure rise.14 However, it is unclear if treating and extending will decrease or prevent chronic elevations in IOP or if it is a cumulative effect of lifetime injections.” Dr. Schehlein checks IOP in a patient. In the short term, intravitreal injections can transiently elevated IOP. Some studies have also shown that sustained IOP elevation can occur. Source: Emily Schehlein, MD GLAUCOMA
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