Inferior implant of XEN63 Gel stent in a refractory open-angle glaucoma due to silicone oil tamponade: A case report

Abstract

Background

To discuss the efficacy of an inferior implant of XEN 63 gel stent in a patient with refractory glaucoma after trabeculectomy failure and vitreoretinal surgery with silicone oil tamponade.

Case Description

We report the case of a 73-year-old man with a history of refractory open glaucoma with trabeculectomy failure. He experienced recurrent retinal detachments with silicone oil tamponade, with uncontrolled intra-ocular pressure (IOP) after silicone oil removal. Due to the presence of oil emulsion in the anterior chamber, the chosen location for XEN 63 implantation was the infero-temporal quadrant. Mild hyphema and vitreous hemorrhage were seen post-operatively, but were self-limiting. At week 1, the intraocular pressure was 8 mmHg with a well-formed bleb seen in anterior segment optical coherence tomography (AS-OCT). At 6 month follow up, the patient maintained a IOP of 12 mmHg without topical hypotensive drugs. Slit lamp examination revealed a widespread, developed bleb with no signs of inflammation.

Conclusion

In this case of refractory glaucoma in a vitrectomized eye with previous oil tamponade, the inferior placement of the XEN 63 gel stent delivered an adequate intraocular pressure even at 6-months follow up, with a diffuse functional infero-nasal bleb seen with AS-OCT.

Introduction

Minimally invasive glaucoma surgery (MIGS) were first proposed as an alternative to filtration surgery in patients with poorly regulated intraocular pressure (IOP) and open-angle glaucoma. MIGS are less invasive and cause less intraoperative and post operative complications if compared to tube surgery (e.g., Ahmed Glaucoma Valve and Baerveldt shunt) and traditional trabeculectomy.^1–3 XEN 45 gel stent (Allergan, Dublin, Ireland) is an approved device for MIGS and can be implanted both ab-interno or ab-externo, allowing for aqueous humor drainage following a subconjunctival pathway for.^4,5

Although numerous studies have demonstrated the positive efficacy/safety profile of XEN 45, there is little data evaluating the outcomes of the novel XEN 63, and those trials were conducted with an earlier iteration of the device during development that was never commercialized and differs in many ways from the current XEN 63 device that is currently on the market (i.e., needle gauge, injector design, implantation technique, etc.).^6–9

The bore of the stent is the unique distinction between XEN 45 and XEN 63. Like the XEN 45 stent, the new XEN 63 device is implanted using a 27G needle. Because the outer diameter of XEN 63 is larger than the outer diameter of XEN 45, there is less side flow with XEN63 than with XEN 45. ¹⁰

In situations of refractory and severe glaucoma, when earlier glaucoma procedures have failed, MIGS are used less often. We present the example of a patient with refractory glaucoma and previous trabeculectomy failure, who underwent several surgeries for recurrent retinal detachment (RD) with silicone oil tamponade. The unresponsive high IOP was effectively treated with a infero-temporal XEN 63 implant.

Case description

A 73-year-old man with a history of hairy cell leukemia, solved with chemotherapy 20 years before, was referred to our clinic. He was already pseudophakic in both eyes and affected by refractory open-angle glaucoma for 5 years, showing poor intraocular pressure (IOP) control with topical hypotensive medications (timolol 5 mg and bimatoprost 0.3 mg). Due to uncontrolled increasing IOP, he underwent uncomplicated mytomicin C (MMC)-augmented trabeculectomy 3 years before in his left eye. During the following 2 years, two surgical bleb revision were required as the IOP began to increase again. Unfortunately, six months later, the patient developed a macula-off rhegmatogenous RD in the same eye. Therefore, he underwent pars plana vitrectomy (PPV) and SF6 endotamponade. One month after, he experienced a recurrence of RD and Silicone oil 1000-cSt was used as endotamponade as proliferative vitreoretinopathy (PVR) was detected. Despite the silicone oil removal was reasonable after a short period of time (4 months) the IOP was not controllable anymore with any topical and systemic medications. In fact, at presentation, his visual acuity was 20/20 on his right eye (RE) and 20/1000 on his left eye. He was treated with a fixed combination of bimatoprost 0.3 mg and timolol 5 mg, along with dorzolamide 20/mg/ml bid, in both eyes. Although the patient referred good treatment adherence, IOP was 14 mmHg in his RE and 28 mmHg in LE. The central corneal thickness was 611 μm in RE and 577 μm in LE, with gonioscopy revealing an open angle morphology. Slit-lamp examination showed a substantial amount of conjunctival fibrosis on the non-effective flat trabeculectomy bleb, in the superior quadrant. Moreover, tiny bubbles of oil emulsion were reported in the anterior chamber (AC). Fundus examination showed silicone-oil filled vitreous chamber, with attached retina in all sectors and laser therapy outcomes in the infero-nasal and infero-temporal sectors.

After obtaining informed consent, the patient was scheduled for placement of a XEN 63 gel stent. Due to silicone oil emulsion visible in the upper sector of the irido-corneal angle, the chosen location for implantation was the infero-temporal quadrant. An intra-Tenon 0.02% MMC injection of 0.1 mL was administered infero-temporally prior to surgery. The XEN 63 stent was then implanted using the classical ab-interno technique: the preloaded injector needle was introduced via a 1.8 mm corneal paracentesis in the supero-nasal quadrant. and the implant's final location was determined via gonioscopy. To verify the stent could move freely, the implant was moved laterally beneath the conjunctiva to check the absence of adhesion.

Two hours after surgery, intraocular pressure was 7 mmHg. Postoperative therapy consisted of a fixed combination of 1 mg/mL of dexamethasone and 3 mg/mL of netilmicin six times daily. At 1 week, the eye exam revealed a small blood clot in the inferior part of the anterior chamber. However we observed a well-formed infero-temporal conjunctival bleb and a IOP of 8 mmHg (Goldmann applanation tonometer). (Figure 1).

Figure 1.

Slit lamp image of the patient left eye six months after XEN 63 gel stent implantation. (a) Tube location is visible at 5 o’ clock in the anterior chamber (white arrowhead). (b) Focus on the inferior diffuse well-formed bleb (white arrows).

On anterior segment optical coherence tomography (AS-OCT), the XEN 63 device was well-positioned in the iridocorneal angle at 5 o’clock of the left eye and a diffuse bleb was present (Figure 2). The examination of the fundus revealed a minor vitreal hemorrhage but no evidence of choroidal detachment. After one month, IOP was 9 mmHg, with complete reabsorption of the clots.

Figure 2.

Anterior segment optical coherence tomography (AS-OCT) showing the position of the XEN 63 gel stent (white arrowhead) in the anterior chamber at 6-months follow up. Posteriorly, the unreflective area (white star) evidence the presence of a well-formed bleb. The patient had an intra-ocular pressure of 12 mmHg. The small bottom-right infrared image of the eye shows the OCT scan direction (red line).

At 6 month follow up, the patient maintained a IOP of 12 mmHg without topical hypotensive medications. Visual acuity was 20/400 and both slit-lamp and AS-OCT analysis revealed a widespread, developed bleb with no signs of inflammation, along with a correctly positioned XEN 63 device.

Discussion

This case describes the efficacy of the XEN 63 gel stent in treating refractory open-angle glaucoma after trabeculectomy failure and a silicone oil induced intraocular pressure decompensation.

After vitreoretinal surgery, silicone-oil induced glaucoma is a common complication, generally due to the migration of emulsified silicone oil into the AC angle. ¹¹ Unfortunately, although silicone oil removal may help in managing IOP in around half of instances, in case of irreparable damage to the trabecular meshwork (TM), the IOP cannot return to normal. For this reason, these conditions may also require further medical or surgical treatments. ¹²

Different reports showed that mitomycin C-augmented trabeculectomy offers poor results in silicone-oil filled eyes, compared to other types of refractory glaucoma, with success rates ranging from 15.5% to 36.9% of cases one year after surgery.^13,14 The use of glaucoma drainage devices showed better results, with cumulative success rates of 62–76% at one year after Ahmed Glaucoma Valve implantation, in different reports.^15,16

Recently, several studies focused on the use of MIGS, and in particular XEN gel stent, in challenging glaucoma settings. The XEN 45 gel stent showed its efficacy in 65 eyes with refractory glaucoma, in a prospective multicenter research conducted by Grover et al. At 12 months, 75.4% of patients had IOP reductions of 20% from baseline while using the same or less medications. ¹⁷ In the setting of uveitic glaucoma, the safety and effectiveness of XEN 45 have been examined, with a 60.2% decrease in IOP from baseline and a significant drop in mean medication consumption (from 3.3 to 0.4 on average). ¹⁸ As far as we know, there's no evidence in literature of XEN 45 gel stent utilization after silicone oil-induced glaucoma.

In our case, a trabeculectomy failure had already been observed one year before vitreo-retinal surgery. Moreover, the silicone oil tamponade may have contributed to the ocular pressure decompesation, due to a quote of emulsified oil presence in the AC, which likely obstructed the TM and the former trabeculectomy. For this reason, in order to avoid the oil-induced blockage of the stent's lumen, we decided for the infero-nasal placement of the device. To our knowledge, due to the few reports regarding XEN 63 gel stent, this is a never-before published technique.

The XEN 63 gel stent is a novel-designed implant with a lumen of 63 µm, which is 1.4 times bigger than the lumen of the XEN 45 device. Similar to the XEN 45 implant, it is inserted with a 27G needle in the iridocorneal angle reaching the subconjunctival space. Due to its bigger lumen, as predictable by the Hagen-Poiseuille equation, the XEN 63 can reduce IOP more than the XEN 45. ¹⁹ Fea et al. performed a short term follow-up research on 23 eyes of patients with open-angle glaucoma who were treated with the XEN 63 gel stent using the 27G needle method, reporting a mean IOP decrease of 41% three months following surgery, with 70% of eyes experiencing an IOP drop of 30% or less without the need of hypotensive medication. ⁶ In a recent retrospective study, XEN 63 showed a significant IOP reduction from 27.0 ± 7.8 mmHg at baseline, to 14.1 ± 3.4 mmHg at the 18-months follow up visit, with a complete success in 60.9% eyes and a drop in the mean number of ocular hypotensive medications (from 2.3 to 1.0). ²⁰ In our case, IOP was still optimally controlled at the six-month follow up, without any hypotensive medication.

Regarding the safety of the XEN 63 gel stent, Fea et al. reported (18%) of hypotony accompanied by choroidal detachments, which resolved without therapy within one month. ⁶ Despite the greater inner diameter of XEN63, the incidence of hypotony was not significantly different compared to the one observed using the XEN 45.^21,22 Other common adverse effects were AC cloat that had already been described as possible post-operative complications of the XEN 45 gel stent as well. ²³

Literature still lack studies regarding the implantation of XEN 63 gel stent in challenging conditions, with only one case report investigating its effectiveness in a refractory uveitic glaucoma following Ahmed Glaucoma Valve failure. In this case, XEN 63 showed mild and transient post-surgical adverse effects, such as a little hyphema, intravitreal hemorrhage and peripheral choroidal detachments due to hypothony, which all cleared at 1 month and did not need a subsequent surgery. Moreover, a good IOP control without hypotensive medications was reported after 12 months. ²⁴ Similarly, in our case, the patient experienced only early self-limiting complications, such as AC clots and tiny vitreous hemorrhage, with slit lamp examination constantly showing a well-formed inferior diffuse bleb through all follow-up visits.

Conclusion

In conclusion, this case demonstrates the efficacy of the XEN 63 gel stent in the treatment of refractory glaucoma after the failure of trabeculectomy, in a eye previously operated with silicon oil endotamponade. However, the long-term efficacy of MIGS in treating refractory glaucoma is unknown and must be assessed.