Comparison of Safety and Efficacy Between Ab Interno and Ab Externo Approaches to XEN Gel Stent Placement

Nicholas E Tan,¹ Nathaniel Tracer,² Anthony Terraciano,³ Hardik A Parikh,² Joseph F Panarelli,² Nathan M Radcliffe<sup>4,5

1</sup>College of Medicine, State University of New York Downstate Health Sciences University, Brooklyn, NY, USA; ²Department of Ophthalmology, NYU Langone Health, New York, NY, USA; ³College of Arts and Sciences, Vanderbilt University, Nashville, TN, USA; ⁴Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY, USA; ⁵New York Eye Surgery Center, Bronx, NY, USA

Correspondence: Nathan M Radcliffe
New York Eye Surgery Center, 1101 Pelham Parkway North, Bronx, NY, USA
Tel +1 718 519 1000
Email drradcliffe@gmail.com

Purpose: To compare the safety and efficacy of two different techniques for implantation of the XEN Gel Stent, a minimally invasive surgical device for the treatment of refractory glaucoma.
Methods: A retrospective chart review of eyes that received ab interno or ab externo XEN Gel Stent placement from February 2017 to October 2019 was conducted. A single surgeon (NMR) performed all operations. Eyes that received the XEN implant concomitant with a glaucoma drainage device insertion or that were lost to 6-month follow-up were excluded. Intraocular pressure (IOP) change, change in glaucoma medications, frequency of slit lamp revision procedures, and frequency of secondary glaucoma surgeries were the primary outcomes compared between groups.
Results: Fifty eyes that underwent ab interno placement and 30 eyes that underwent ab externo placement were studied. The ab interno cohort demonstrated a mean IOP reduction of 8.4 ± 1.7 mmHg (28.6% decrease) by 12 months, compared to a mean reduction of 12.8 ± 3.0 mmHg (40.1% decrease) in the ab externo group (p = 0.208). Mean reduction in medication use was 1.81 ± 0.29 medications in the ab interno group and 1.86 ± 0.37 in the ab externo group (p = 0.913). By 12 months, 58% of ab interno eyes had required 5-fluorouracil injection compared to 36.7% of ab externos (p = 0.105). Bleb needling was applied to 42% and 26.7% of the eyes, respectively (p = 0.231). A second glaucoma surgery was necessary for 20% of the ab interno cohort and 10% of the ab externo cohort (p = 0.351).
Conclusion: There were no differences in outcomes between ab interno and ab externo placement of the XEN Gel Stent. Both approaches are safe and effective for lowering IOP.

Keywords: MIGS, glaucoma surgery, bleb, subconjunctival stent, surgical technique