A Retrospective Analysis of Safety and Efficacy of XEN 45 Microstent Combined Cataract Surgery in Open-Angle Glaucoma over 24 Months

Sevgi Subaşı; Nurşen Yüksel; Fevzi Özer; Büşra Yılmaz Tugan; Dilara Pirhan

doi:10.4274/tjo.galenos.2020.47629

ABSTRACT

Conclusion:

XEN 45 is an effective minimally invasive surgical treatment for OAG with significant reduction in IOP and glaucoma medications and minimal complications in long-term follow-up.

Results:

After the XEN 45 combined cataract surgery procedure, IOP dropped from 20.37±4.80 mmHg with a mean of 3.07±1.04 medication classes preoperatively to 14.83±1.91 mmHg with a mean of 0.94±1.11 medication classes at 24 months (p=0.001 for both). At 24 months, 55.6% of patients had IOP ≤18 mmHg without medication, 94.4% of patients had IOP ≤18 mmHg with or without medication, and 61.1% of patients reached ≥20% IOP reduction from baseline.

Materials and Methods:

In this retrospective study, 30 eyes of 25 patients with OAG which underwent XEN 45 implantation combined with simultaneous phacoemulsification were clinically evaluated. Clinical outcomes analyzed included IOP, percent of IOP reduction, medication use, complications, best corrected visual acuity, and surgical outcomes at 24-month follow-up.

Objectives:

To evaluate the effect on intraocular pressure (IOP) reduction and safety of ab interno gelatin microstent (XEN 45 Gel Stent; Aquesys, Inc, Aliso Viejo, CA, USA) microincisional glaucoma/cataract surgery in open-angle glaucoma (OAG).

Keywords:

Cataract surgery, microincisional glaucoma surgery, open-angle glaucoma, XEN 45 Gel Stent

Patients and Assessments

We retrospectively analyzed 30 eyes of 25 patients who were treated with XEN 45 implantation with mitomycin C (MMC) combined with cataract surgery by the same surgeon at the Kocaeli University Department of Ophthalmology between January 2016 and January 2018. The Local Ethics Committee of the Kocaeli University approved the study, which was conducted in accordance with the tenets of the Declaration of Helsinki.

Inclusion criteria for the Diagnostic Innovations in Glaucoma Study of primary OAG (POAG) were glaucomatous optic neuropathy in clinical examination including thinning of neuroretinal rim with retinal nerve fiber layer loss, visual field (VF) defect, and open angle confirmed with gonioscopy.¹¹ The diagnosis of pseudoexfoliation glaucoma (PXG) was based on clinically visible criteria on slit-lamp examination (accumulated extracellular material in the anterior segment of the eye) with the parameters mentioned above.¹² This study included eyes with primary and secondary (pseudoexfoliation) OAG and previously diagnosed cataract that had not reached target IOP or showed progressive VF loss with maximum medical therapy, as well as eyes of patients with medication intolerance or nonadherence.

Exclusion criteria were angle-closure, congenital, and neovascular glaucoma, prior uveitis or endophthalmitis, ocular surgery history (except glaucoma surgery), and aphakia. The patients who fulfilled these inclusion criteria and underwent combined cataract surgery and XEN 45 microstent implantation were evaluated in this retrospective case study.

Complete ophthalmic examination including visual acuity, gonioscopic evaluation, IOP measurement by Goldmann applanation tonometry, anterior and posterior segment evaluation, cup/disc ratio, central corneal thickness (CCT) with a fully automatic tonometer (Canon TX-20P, Tokyo, Japan), VF testing 30-2 strategies with a Humphrey Field Analyzer model 750I (Carl Zeiss Meditec, Dublin, CA, USA), and optical coherence tomography (SD-OCT, Heidelberg Engineering, Germany) were performed preoperatively (baseline) and at 1, 3, 6, 12, and 24 months postoperatively. Thirty eyes completed 12 months and 18 eyes completed 24 months of follow-up. None of the patients were excluded from analysis. Glaucoma staging was done according to mean deviation values (mild: >-6 dB, moderate: -6 to -12 dB, and severe: <-12 dB) as described in the European Glaucoma Society Guidelines.¹³

Primary outcome measures included IOP, mean IOP reduction, percentage of IOP reduction, the number of antiglaucoma medications used and their changes in repeated measures, IOP reduction ≥20%, the mean categorized IOP (8-12 mmHg, >12-15 mmHg, >15-18 mmHg, >18 mmHg), postoperative complications, logarithm of the minimal angle of resolution (LogMAR) best corrected visual acuity (BCVA), and vision changes (gain of ≥2 lines, stable, or loss of ≥2 lines; clinically significant change in BCVA was defined as 0.2 units of logMAR) during 24-month follow-up.¹⁴

Secondary efficacy outcomes were determined as the rate of needling and complete and qualified success rates. Complete success was defined as a postoperative IOP ≤18 mmHg but not <5 mmHg with ≥20% reduction in IOP without medication. Qualified success was defined as a postoperative IOP ≤18 mmHg but not <5 mmHg with ≥20% reduction in IOP with or without medication.¹⁵

Introduction

Glaucoma is an important cause of blindness and affects 3.54% of people worldwide.¹ The purpose of treatment is to reduce intraocular pressure (IOP) via various treatment strategies in order to halt optic nerve injury.² The most common surgeries are traditional incisional surgeries which provide the drainage of aqueous fluid to the subconjunctival space with an ab externo approach.³ Although these methods have been successful in reducing IOP, both trabeculectomy and aqueous tube shunts come with a range of short- and long-term complications like hypotony, leakage, scarring, foreign body sensation associated with blebs, astigmatism, secondary cataracts, blebitis, endophthalmitis, and choroidal hemorrhage.^3,4,5,6

Minimally invasive glaucoma surgery (MIGS) is less invasive than traditional incisional surgeries and offers more modest results with the benefit of a safe risk profile in patients with mild to moderate glaucoma.⁷ The four main approaches to IOP reduction include increasing trabecular outflow, increasing uveoscleral outflow via suprachoroidal pathways, reducing aqueous production from the ciliary body, and creating a subconjunctival drainage pathway via an ab interno incision.⁷

The XEN 45 Gel Stent (Aquesys, Inc., Aliso Viejo, CA, USA) is a hydrophilic tube composed of gelatin crosslinked with glutaraldehyde, with the smallest model having an inner diameter of 45 µm and a length of 6 mm, which creates subconjunctival drainage like traditional incisional glaucoma surgeries with an ab interno microincisional approach.^8,9 It was created with adequate length, tube rigidity, and lumen diameter to limit flow and avoid hypotony by using the Hagen-Poiseuille equation.^8,10

This retrospective analysis aimed to assess the results of combined glaucoma/cataract surgery using the smallest diameter XEN 45 Gel Stent in regard to IOP-lowering effect, visual acuity, and postoperative complications in open-angle glaucoma (OAG) patients.

Materials and Methods

Results

Discussion

Although cataract surgery provides a decrease in IOP, additional glaucoma surgery is required in some glaucoma patients.^16,17,18 Combined procedures with traditional surgery methods had additional risks related to the surgery type.^4,19 Because of this, new MIGS techniques were adopted. The XEN 45 Gel Stent is an apparatus that shunts aqueous to the subconjunctival space via a minimally invasive ab interno approach. This type of subconjunctival drainage avoids the risk of outshow obstruction while lowering IOP, and the XEN Gel Stent is the only filtering MIGS device that works in this way. The ab interno installation of the device provides safety with a low rate of long-term complications. Although some complications have been reported as case reports, rates of serious complications are lower than in traditional surgery.²⁰

In a prospective clinical study with XEN 45 Gel Stent combined cataract surgery, 80.4% of patients had IOP ≤18 mmHg at 12 months.²¹ In a multicenter open-label study, 75.4% of patients had ≥20% IOP lowering from baseline on the same or fewer medications at 12 months, while this rate was 70.0% in our study.²² Similar to the literature, 61.1% of patients reached ≥20% IOP reduction from baseline and 94.4% of patients had IOP ≤18 mmHg at 24 months in our study. The percentage of IOP reduction could differ according to baseline IOP and the indication (medication intolerance or nonadherence). Moreover, almost all patients had IOP ≤18 mmHg with a lower number of medications at 12 months and this benefit continued over 24 months.

IOP reduction of 36.4% and 30% was reported in clinical studies with XEN 140 without MMC and with XEN 140 and XEN 63 combined with cataract surgery without MMC, respectively.^23,24 In a prospective study of the XEN 45 microimplant with MMC, 29.4% reduction in IOP was reported.²⁵ Our IOP reductions were 23.3% and 27.2% at months 12 and 24, respectively. Different degrees of IOP reduction could be related to the proportion of patients with well-controlled IOP in study populations and the distribution of patients with different types of OAG. The results vary depending on many factors such as the type of XEN stent used, whether glaucoma surgery is applied in conjunction with cataract surgery, and the use of MMC, but sufficient IOP lowering and decreased medication use are reported in all studies. Ozal et al.²⁶ reported that the patients who underwent cataract surgery with XEN implantation and those who underwent only XEN implantation were similar in terms of IOP reduction. In our study, combined cataract surgery with XEN implantation was applied to all patients because they had cataracts and glaucoma. Therefore, no comparison was made in terms of these conditions in our study. When evaluated in the light of the literature data, as XEN implantation is an ab interno surgery that does not cause conjunctival damage, it is thought that inflammation induced by cataract surgery will not affect surgical success as much as trabeculectomy. Combined surgery also decreases the burden of multiple surgeries.

At 12 and 24 months, the qualified success rates of our procedure were 70% and 61.1%, and complete success was achieved in 40% and 33.3%, respectively. Using the same criteria for complete and qualified success, Gillmann et al.²⁷ reported complete success rates of 24.5% and 36.4% and qualified success rates of 30.6% and 38.6% at 24 months in their POAG and PXG groups, respectively. Many factors can determine surgical success, including low baseline and postoperative IOP and higher number of baseline medications, because the success rate calculations are based on both postoperative IOP 5-18 mmHg and ≥20% IOP reduction.²⁷

The rate of needling was 43.3% in our study, 47% in a study by Sheybani et al.²³ in which MMC was not used, 30.7% in a study by Galal et al.²⁵, 27% in a study by Hengerer et al.²⁵ in which MMC was used during implantation, and 43.0% in the study by Gillmann et al.²⁷ in which MMC was used. We thought that the difference between percentages could be related to MMC use and the profile of the study groups (PXG, POAG, and pigmentary glaucoma). According to our results, PXG patients required more needling interventions than POAG patients, but this difference was not statistically significant. Average needling times were reported as 4.5 months by Mansouri et al.²⁸ and between 1 week and 3 months by Hengerer et al.²⁴ In our study, the mean time to needling was between 1 week and 3 months in 84.6% of patients.

Conclusion

This study has limitations such as the small sample size and noncomparative design. Nevertheless, we provided valuable data for clinicians when choosing the procedure for their patients. This retrospective study demonstrated that XEN 45 implantation in patients with inadequately controlled IOP despite maximum medical therapy or in patients with medication intolerance or nonadherence provided significant reductions in IOP and medication use and improved visual acuity with high success rates and low complication rates during follow-up.

References

Tham YC, Li X, Wong TY, Quigley HA, Aung T, Cheng CY. Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis. Ophthalmology. 2014;121:2081-2090.

Heijl A, Leske MC, Bengtsson B, Hyman L, Bengtsson B, Hussein M; Early Manifest Glaucoma Trial Group. Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial. Arch Ophthalmol. 2002;120:1268-1279.

Gedde SJ, Herndon LW, Brandt JD, Budenz DL, Feuer WJ, Schiffman JC; Tube Versus Trabeculectomy Study Group. Postoperative complications in the tube versus trabeculectomy (TVT) study during ﬁve years of follow-up. Am J Ophthalmol. 2012;153:804-814.

Topouzis F, Coleman AL, Choplin N, Bethlem MM, Hill R, Yu F, Panek WC, Wilson MR. Follow-up of the original cohort with the Ahmed glaucoma valve Implant. Am J Ophthalmol. 1999;128:198-204.

Topouzis F, Yu F, Coleman AL. Factors associated with elevated rates of adverse outcomes after cyclodestructive procedures versus drainage device procedures. Ophthalmology. 1998;105:2276-2281.

Richter GM, Coleman AL. Minimally invasive glaucoma surgery: current status and future prospects. Clin Ophtalmol. 2016;10:189-206.

Sheybani A, Reitsamer H, Ahmed II. Fluid dynamics of a novel micro-ﬁstula implant for the surgical treatment of glaucoma. Invest Ophthalmol Vis Sci. 2015;56:4789-4795.

Lewis, Richard A. Ab interno approach to the subconjunctival space using a collagen glaucoma stent. J Cataract Refract Surg. 2014;40:1301-1306.

McLaren JW. Measurement of aqueous humor show. Exp Eye Res. 2009;88:641-647.

Verges C, Cazal J, Lavin C. Surgical strategies in patients with cataract and glaucoma. Curr Opin Ophthalmol. 2005;16:44-52.

Sample PA, Girkin CA, Zangwill LM, Jain S, Racette L, Becerra LM, Weinreb RN, Medeiros FA, Wilson MR, De León-Ortega J, Tello C, Bowd C, Liebmann JM; African Descent and Glaucoma Evaluation Study Group. The African Descent and Glaucoma Evaluation Study (ADAGES): Design and Baseline Data. Arch Ophthalmol. 2009;127:1136-1145.

Ritch R. Ocular and systemic manifestations of exfoliation syndrome. J Glaucoma. 2014;23(8Suppl 1):1-8.

No authors listed. European Glaucoma Society Terminology and Guidelines for Glaucoma, 4th Edition - Chapter 2: Classification and terminologySupported by the EGS Foundation: Part 1: Foreword; Introduction; Glossary; Chapter 2 Classification and Terminology. Br J Ophthalmol. 2017;101:73-127.

Lenzhofer M, Strohmaier C, Hohensinn M, Hitzl W, Steiner V, Baca B, Moussa S, Motloch K, Reitsamer HA. Change in visual acuity 12 and 24 months after transscleral ab interno glaucoma gel stent implantation with adjunctive Mitomycin C. Graefes Arch Clin Exp Ophthalmol. 2019;257:2707-2715.

Kalina AG, Kalina PH, Brown MM. XEN® Gel Stent in Medically Refractory Open-Angle Glaucoma: Results and Observations After One Year of Use in the United States. Ophthalmol Ther. 2019;8:435-446.

Casson RJ, Salmon,JF. Combined surgery in the treatment of patients with cataract and primary open-angle glaucoma. J Cataract Refract Surg. 2001;27:1854-1863.

Poley BJ, Lindstrom RL, Samuelson TW. Long-term effects of phacoemulsification with intraocular lens implantation in normotensive and ocular hypertensive eyes. J Cataract Refract Surg. 2008;34:735-742.

Liaska A, Papaconstantinou D, Georgalas I, Koutsandrea C, Theodosiadis P, Chatzistefanou K. Phaco-trabeculectomy in controlled, advanced, open-angle glaucoma and cataract: parallel, randomized clinical study of efficacy and safety. Semin Ophthalmol. 2014;29:226-235.

Sheybani A, Dick HB, Ahmed II. Early Clinical Results of a Novel Ab Interno Gel Stent for the Surgical Treatment of Open-angle Glaucoma. J Glaucoma. 2016;25:691-696.

Olgun A, Imamoğlu S, Karapapak M, Düzgün E, Kaçar H. Endophthalmitis after XEN gel stent implantation: 2 cases. J Glaucoma. 2018;27:191-194.

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. 2018;38:1129-1134.

Grover DS, Flynn WJ, Bashford KP, Lewis RA, Duh YJ, Nangia RS, Niksch B. Performance and Safety of a New Ab Interno Gelatin Stent in Refractory Glaucoma at 12 Months. Am J Ophthalmol. 2017;183:25-36.

Sheybani A, Lenzhofer M, Hohensinn M, Reitsamer H, Ahmed II. Phacoemulsification combined with a new ab interno gel stent to treat open-angle glaucoma: Pilot study. J Cataract Refract Surg. 2015;41:1905-1909.

Hengerer FH, Kohnen T, Mueller M, Conrad-Hengerer I. Ab Interno Gel Implant for the Treatment of Glaucoma Patients With or Without Prior Glaucoma Surgery: 1-Year Results. J Glaucoma. 2017;26:1130-1136.

Galal A, Bilgic A, Eltanamly R, Osman A. XEN Glaucoma Implant with Mitomycin C 1-Year Follow-Up: Result and Complications. J Ophthalmol. 2017;2017:5457246.

Ozal SA, Kaplaner O, Basar BB, Guclu H, Ozal E. An innovation in glaucoma surgery: XEN45 gel stent implantation. Arq Bras Oftalmol. 2017;80:382-385.

Gillmann K, Bravetti GE, Mermoud A, Rao HL, Mansouri K. XEN Gel Stent in Pseudoexfoliative Glaucoma: 2-Year Results of a Prospective Evaluation. J Glaucoma. 2019;28:676-684.

Mansouri K, Guidotti J, Rao HL, Ouabas A, D’Alessandro E, Roy S, Mermoud A. Prospective evaluation of standalone XEN gel implant and combined phacoemulsification-XEN gel implant surgery: 1-year results. J Glaucoma. 2018;27:140-147.

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