We were fascinated by the article by Ferguson et al.1 The authors showed that trabecular microbypass stent (iStent, Glaukos Corp.) implantation combined with cataract surgery safely and effectively lowered intraocular pressure (IOP) and the need for medication in patients with mild, moderate, and severe stages of pseudoexfoliation glaucoma (PXG). Promising findings suggest that microinvasive glaucoma surgery (MIGS) is a noteworthy alternative to traditional filtering procedures in patients with PXG, the most common form of secondary open-angle glaucoma.2 At present, the lack of randomized clinical trials and comparative data on different new MIGS devices hinder evaluation of the primary alternative in PXG.
We focused on evaluating the use of the Xen 75 Gel stent (preloaded into a Xen Injector, Allergan, Inc.),3,4,A an ab interno hydrophilic collagen tube with a 45 μm lumen directing aqueous flow to the subconjunctival space, combined with cataract surgery in PXG. Intraoperatively, 10 μg of mitomycin-C (MMC) was injected into the sub-Tenon space to create a posterior bleb. The operations were performed by the same surgeon (R.M.).B Postoperatively, the patients were prescribed topical dexamethasone sodium phosphate (Oftan Dexa) 1 mg/mL 6 times a day for the first month and then tapered to 4 times a day for the second month and twice a day for the third month. The safety and efficacy of the gel stent combined with cataract extraction were recorded on the predetermined postoperative visits at 1 day, 1 week, 1 month, 2 months, 3 months, and 6 months.
This study comprised 10 patients (6 women, 4 men) with a mean age of 77.4 years ± 5.7 (SD). The mean time from diagnosis of glaucoma was 9.4 ± 7.6 years with a mean IOP at the time of diagnosis of 33.0 ± 9.1 mm Hg. Preoperatively the mean cup-to-disc ratio was 0.87 ± 0.07, the mean decimal corrected distance visual acuity (CDVA) was 0.36 ± 0.16, the mean IOP was 21.1 ± 7.3 mm Hg, and the mean number of glaucoma medications needed was 2.4 ± 1.1.
After surgery, the mean IOP was 9.9 ± 5.1 mm Hg (47.1% ± 33.5% IOP reduction, no medication) at 1 day, 9.6 ± 4.0 mm Hg (52.0% ± 23.1% IOP reduction, no medication) at 1 week, 11.5 ± 6.1 mm Hg (45.4% ± 16.4% IOP reduction, no medication) at 1 month, 12.7 ± 3.4 mm Hg (38.1% ± 12.1% IOP reduction, 0.3 ± 0.7 medication) at 2 months, 13.5 ± 3.8 mm Hg (33.0% ± 20.5% IOP reduction, 0.3 ± 0.7 medication) at 3 months, and 10.2 ± 3.6 mm Hg (47.4% ± 23.0% IOP reduction, 0.9 ± 1.4 medication) at 6 months (Figure 1). The mean decimal CDVA improved to 0.82 ± 0.30.
During the postoperative follow-up, 1 eye required needling/bleb revision without MCC to direct flow. One eye showed decreased flow because of pigment blockade at the lumen of the stent at the 1- to 3-month follow-up. The blockade had cleared and the flow had improved by 6 months. No avascular blebs were observed.
Randomized clinical trials with a longer follow-up are justified; however, new MIGS devices, such as the gel stent, hold promise in achieving reasonable and safe IOP reduction in PXG.
1. Ferguson TJ, Swan R, Ibach M, Schweitzer J, Sudhagoni R, Berdahl JP. Trabecular microbypass stent implantation with cataract extraction in pseudoexfoliation glaucoma. J Cataract Refract Surg
2. Aboobakar IF, Johnson WM, Stamer WD, Hauser MA, Allingham RR. Major review: Exfoliation syndrome; advances in disease genetics, molecular biology, and epidemiology. Exp Eye Res
3. Galal A, Bilgic A, Eltanamly R, Osman A. XEN glaucoma implant with Mmitomycin C 1-year follow-up: result and complications. J Ophthalmol 2017. article ID:5457246. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5350531/pdf/JOPH2017-5457246.pdf
4. De Gregorio A, Pedrotti E, Russo L, Morselli S. Minimally invasive combined glaucoma and cataract surgery: clinical results of the smallest ab interno gel stent. Int Ophthalmol 2017 May 29. [Epub ahead of print].
Other Cited Material
A. U.S. National Institutes of Health Clinical Trials. An Innovation in Glaucoma Surgery: XEN45 Gel Stent Implantation. NCT03138928. Available at: https://clinicaltrials.gov/ct2/show/NCT03138928
. Accessed July 6, 2017
B. Tuuminen R. Combined cataract surgery and Xen Gel Stent implantation [video]. Available at: http://www.hrrg.fi/en/videos/migs
. Accessed July 6, 2017