XEN-45 Implant Shows Promise for Treating Patients with Uncontrolled Uveitic Glaucoma

Credit: ResearchGate

A new study found the XEN-45 hydrophilic collagen implant is effective for treating patients with uncontrolled uveitic glaucoma, although may lead to sight-threatening postoperative complications like bleb-related ocular infection and persistent hypotony.¹

The XEN-45 implant is made up of cross-linked porcine gelatin, which drains aqueous from the anterior chamber to the subconjunctival space. The implant has an inner lumen of about 45 μm, large enough to supply about 6 – 8 mmHg pressure resistance.

The XEN-45 implant had yet to be studied in patients with uveitic glaucoma, so a new study, led by Chelvin C. A. Sng, MMed, MRCSEd, FRCSEd, FAMS, of the department of ophthalmology at National University Health System in Singapore and the Singapore Eye Research Institute, wanted to evaluate the safety and efficacy of the XEN-45 collagen implant in eyes with uveititc glaucoma. According to the American Academy of Ophthalmology, uveitic glaucoma affects 20% of uveitis patients.²

“The 12-month efficacy of the XEN-45 implant in our study is unexpectedly encouraging for a MIGS device, the efficacy of which is thought to be modest compared to conventional glaucoma filtration surgery in exchange for a more favourable safety profile,” the investigators wrote.¹ “Our preliminary results suggest that the XEN-45 implant may be more effective in lowering the IOP compared to other available MIGS devices.”

The investigators conducted an exploratory prospective single-cohort study with 24 patients aged 45.3 ± 18.1 years old with medically uncontrolled uveitic glaucoma. Before the surgery, patients needed ≤ 3 glaucoma medications and 11 patients needed oral acetazolamide (≥ 500 mg/day). Every patient had open angles (Shaffer grade 3 or 4), as well as free, mobile conjunctiva in the target superior-nasal quadrant.

The primary outcome examined intraocular pressure at 14 months versus baseline. Then, the secondary outcome examined ocular hypotensive medication use at 12 months, as well as the requirement for further glaucoma surgery and failure.

The investigators injected 0.1 ml of 0.2 mg/mL mitomycin C subconjunctivally in the superior-nasal quadrant of the eye for 5 – 10 minutes before implanting the XEN-45. They made a 1.1 mm corneal incision in the inferior-temporal cornea with a 20-gauge MVR knife at the 4 o’clock position for the left eye and a 10 o’clock position for the right eye.

The investigators filled the anterior chamber with viscoelastic and inserted the preloaded inserter needle. Then, the investigators implanted the XEN-45 into the subconjunctival space and withdrawn the injector needle from the eye. After surgery, patients stopped taking all glaucoma medications and were prescribed topical antibiotics for 2 weeks and topical dexamethasone 0.1% for 3 months.

Participants completed an ophthalmic examination on day 1, week 1, and months 1, 3, 6, 9, and 12, including slit lamp examination, best corrected Snellen visual acuity assessment, and intraocular pressure measurement. The investigators also performed a gonioscopy to grade the Shaffer classification and to confirm the implant was in the correct place.

The team defined surgery failure as an intraocular pressure of > 21 mmHg or less than 20% reduction. Patients had exceeded this, demonstrating the success of the surgery.

At baseline, the mean intraocular pressure was 30.5 ± 9.8 mmHg. For patients who thought conventional glaucoma surgery was inevitable, 83.3% of the eyes (n = 20), no longer needed surgery following the XEN-45 implantation. Meanwhile, 4 eyes (16.7%) required extra incisional glaucoma surgery due to uncontrolled intraocular pressure.

Surgery reduced the mean intraocular pressure by 60.2% from baseline to 12.2 ± 3.1 mmHg (P < .001). After the implantation, 1 patient had hypotony lasting over 2 months, signaling they needed surgical revision. Also, 1 patient developed blebitis. The study has a 79.2% 12-month cumulative Kaplan-Meier survival probability.

The surgery had not led to sight-threatening intraoperative complications. Except, 1 eye had intraoperative hyphaema due to the implant being inserted too posteriorly. The implant was removed and replaced with a second one.

Participants did experience some postoperative complications, such as:

• Transient postoperative intraocular pressure, occurring in 15% eyes (62.5%)
• Intraocular pressure elevation (9 eyes, within the first 3 months of the implant).
• Requiring postoperative bleb needling at the slit lamp (10 eyes (41.7%) to get a diffuse bleb morphology.
• Bleb revision with Tenon’s dissection (5 eyes with extensive subconjunctival scarring around the implant in association with raised intraocular pressure; within 4 months after surgery).
• Postoperative hyphemia (2 eyes (8.3%); resolved 1 week after surgery).
• Postoperative hypotony (9 eyes (37.5%); fixed within 2 weeks in 8 eyes. 5 eyes had hypotony related to a shallow anterior chamber and needed anterior chamber reformation with viscoelastic.
• Persistent hypotony and choroidal effusion (1 patient; 2 months after the surgery)
• Implant exposure (2 eyes required conjunctival closure at postoperative month 3 and 4, respectively)
• Lost ≥ 2 lines of BCVA (3 eyes (12.5%), caused by cataract progression after implant).
• Blebitis (1 eye (4.2%); caused by an avascular bleb and occurred 9 months after the implant.

“This pilot study provides novel data on the clinical efficacy of the XEN-45 implant in eyes with uveitic glaucoma,” the investigators wrote. “Our results suggest that XEN-45 implantation is an effective treatment option for patients with medically uncontrolled uveitic glaucoma, averting conventional glaucoma surgery in 83.3% of patients and 62.5% of the eyes were medication-free for at least 12 months.”

^References

1. ^{Sng CC, Wang J, Hau S, Htoon HM, Barton K. XEN-45 collagen implant for the treatment of uveitic glaucoma. Clin Exp Ophthalmol. 2018;46(4):339-345. doi:10.1111/ceo.13087}
2. ^{Uveitic Glaucoma. American Academy of Ophthalmology. https://eyewiki.aao.org/Uveitic_Glaucoma.Accessed December 7, 2023.}