A new device to manage glaucoma, developed in part with Australian researchers, is now available in Australia.1,4 The Xen Gel Implant can be used to reduce intraocular pressure in patients with primary open angle glaucoma where previous medical treatments have failed.1,2 It is now entered in the Australian Register of Therapeutic Goods (ARTG), and reimbursed on the Private Health Insurance Prostheses list.3
Incorporating technology created by Professor William Morgan and Professor Dao-Yi Yu at the Perth Lions Institute over 20 years ago,4 the Xen Gel Implant has been shown to be effective and efficient at achieving sustained low-teen intraocular pressure (IOP) lowering, with over half of patients drop free at 12 months.5
While there are a number of devices and surgical approaches for treating glaucoma, complications are still a major problem.6 Trabeculectomy, for example, can pose challenges for the surgeon due to bleb leaks, subconjunctival fibrosis and unpredictable flow.7
This is welcome news for ophthalmologists
The Xen Gel Implant, although based on the same principle as trabeculectomy, takes advantage of an ab interno approach, eliminating external manipulation of the eye and reducing the risk of complications such as cataract and hypotony.6,7
The implant is unique in that it is the only available Minimally Invasive Filtration Surgery (MIFS) device and delivers subconjunctival filtration similar to a trabeculectomy.8 It is a 6mm long biocompatible, tissue-conforming implant that becomes soft and flexible when hydrated,6,9 creating a permanent pathway from the anterior chamber to the subconjunctival space to form a diffuse, lowlying bleb.6 The outflow channel formed by the implant bypasses trabecular and scleral resistance to decrease intraocular pressure.6
The Xen Gel Implant has been developed with a 45μm tube, which provides around 6–8mmHg flow resistance, which reduces risk of hypotony.6 It is designed as a standalone procedure but can be combined with cataract surgery.5
The implant is time efficient; approximately three Xen procedures can be done in the time required for one trabeculectomy.10,11 It has a less intensive and time-consuming follow up than trabeculectomy,10,11 and importantly for patients, a reduced risk of post-operative complications versus trabeculectomy.11,12 It also has shown improved best corrected visual acuity (BCVA) compared to trabeculectomy.12
Associate Professor Andrew White, from the University of Sydney and Westmead Hospital commented, “This is welcome news for ophthalmologists and the wider eye care community, giving us another tool to help improve outcomes for the hundreds of thousands of patients living with glaucoma. Xen gives us a less invasive and labour intensive option than the traditional trabeculectomy.”5,6
“The Xen will not completely replace trabeculectomy but the improved visual rehabilitation13 and sutureless procedure,6 may assist with improved patient comfort and gives us another valuable surgical option in the fight against glaucoma,” concluded Associate Professor White.
Associate Professor Michael Coote, Ophthalmologist, from Melbourne Eye Specialists added “Xen also has a reduced risk of complications and less time consuming patient follow up, which is an important benefit for both clinicians and patients. For patients, the reduced complications and earlier return to visual acuity may mean an earlier return to daily life, which is an important quality of life benefit.”10,12
Glaucoma is the leading cause of irreversible blindness worldwide14,15 and approximately 300,000 people in Australia have glaucoma.16 Two in 100 Australians will develop glaucoma in their lifetime, and this risk increases with age; one in eight Australians aged over 80 years will develop glaucoma.16 Currently, about 50 per cent of people with glaucoma remain undiagnosed.16
Results from the available 12 month interim data from a now completed 24 month clinical trial (APEX) found that 70 per cent of people with the Xen Gel Implant achieved equal to or less than 15mmHg IOP, with the mean IOP at 13.8mmHg, from a treated baseline of 21.4mmHg.5
Furthermore, 56 per cent of patients were drop free at 12 months and mean IOP lowering medications were reduced from 2.6 to 0.6 at 12 months (p<0.0001).5 There was no symptomatic hypotony or major complications.5
As the Xen Gel Implant procedure is a filtration procedure, you can expect to see similar adverse events to a trabeculectomy.6,13 Only a small percentage of Xen Gel Implant patients experienced hypotony-related adverse events, including 1.3 per cent choroidal effusion (self-limited, lasting <30 days) and 0.4 per centanterior chamber refill.2,5,17
References
1. Department of Health. Australian Register of Therapeutic Goods (ARTG) Public Summary for XEN. Viewed 7 June 2018. Available from: www.ebs.tga.gov.au/servlet/xmlmillr6?dbid=ebs/PublicHTML/pdfStore.nsf&docid=BFC708E516AAC017C A2581FD003CA9A9&agid=(PrintDetailsPublic)&actionid=1
2. Allergan Xen Directions for use
3. Department of Health, The Prostheses List. Viewed 7 June 2018. Available from: www.health.gov.au/internet/main/publishing.nsf/content/69F6A026037D6093CA257BF0001B5EDA/$File/February%202018%20Prostheses%20List%20-%20New%20Items.pdf.
4. Lions Eye Institute’s glaucoma treatment wins approval, The Australian, 21 March 2018. Viewed 7 June 2018. Available from www.theaustralian.com.au/higher-education/lions-eye-institutes-glaucoma-treatmentwins-approval/news-story/7dc1570aa954922fec37ae15ed4cd29a
5. Stalmans I. A Minimally Invasive Approach to Sub-conjunctival Outflow: 1 Year Results of an Ab-interno Gelatin Stent for the Treatment of Primary Open Angle Glaucoma. Poster Presented at International Congress Glaucoma Surgery, February 2016, Muscat, Oman.
6. Vera VI and Hovarth C. 2014 Surgical Innovations in Glaucoma. (17): 189-198. New York, Springer Media.
7. Glaucoma Australia. Trabeculectomy Fact Sheet. Viewed 7 June. Available from: www.glaucoma.org.au/media/1182/trabeculectomy-glaucoma-surgery-pdf-aw1013112.pdf
8. De Gregorio A et al. Int Ophthalmol 2018; 38(3):1129-1134
9. Lewis R.A. et al. J Cataract Refract Surg 2014;40:1301–6
10. Dapena CL and Ros RC. Revista Espanola de Glaucoma e Hipertension Ocular. 2015; 5(3): 350-357.
11. Glaucoma Foundation. FAQ- What’s the recovery time for laser and trabeculectomy surgery? Viewed 8 June 2018. Available from: www.glaucomafoundation.org/info_new.php?id=156&cat=9#201
12. Schlenker M.B. et al. Ophthalmol. 2017;124:1579-1588
13. Gulamhusein H et. al Standalone Ab Interno Gelatin Stent with MMC Versus Standalone Trabeculectomy with MMC: Post-operative Patient Experience and Healthcare Utilization. Presented at American Glaucoma Society Annual Meeting, March 2017, Coronado, US.
14. Tham Y-C et al. Ophthalmol. 2014;121(11):2081–90.
15. Glaucoma Australia. Facts & FAQs. Viewed 7 June 2018. Available from: www.glaucoma.org.au/aboutglaucoma/facts-and-faqs/
16. Glaucoma Australia. What is Glaucoma Viewed 7 June 2018. Available from: www.glaucoma.org.au/about-glaucoma/what-is-glaucoma/
17. Allergan Data on file INT/0011/2016
