Surgeons share their experience of a new approach to gel stent implantation

Reviewed by Dr Ike K. Ahmed

According to Dr Razeghinejad et al, since 1856-when Albrecht von Graefe discovered that iridectomy was an effective surgical method for acute glaucoma treatment-many new surgeries have been devised. Two years following Dr von Graefe’s achievements, Louis De Wecker presented sclerotomy as a procedure for chronic glaucoma and in 1900, internal filtration (cyclodialysis) was developed.

Although the majority of surgeries used nowadays were introduced in the 1960s, their roots can be traced to the work of surgeons in the 19th century.¹ In a bid to mitigate the intra- and post-operative complications associated with glaucoma surgery, there have been some recent new additions to the story. For example, new minimally invasive glaucoma surgeries (MIGS) have been developed from devices such as the Trabectome (NeoMedix Inc), the iStent (Glaukos), the Hydrus (Ivantis) and the CyPass Suprachoroidal Microstent (Transcend Medical).^2,3

Today, newer MIGS are designed to offer the same benefits as traditional surgeries but with faster patient recovery (the injectable technique is tissue-sparing and minimally invasive⁵ compared with classic filtration surgery), less intensive post-operative procedure follow-up and fewer initial appointments in the first month(s) after the procedure.^6,7,8

While MIGS are sometimes costly, a recent study reported an IOP reduction of around 30%. In addition, 2.9 fewer glaucoma medications per patient at one year were required.⁴ So, according to Dr Ike Ahmed, a LASIK surgeon in Canada: “The overall life and eye-health benefits often outweighs the costs of surgery, depending on where you are in the world.”

The ‘Three Ps’

At the width of a human hair and just 6-mm long, Allergan’s MIGS device (XEN gel stent) is inserted via a small, self-sealing corneal incision using a simple preloaded injector. According to its producers, it is the only glaucoma implant made from soft, pliable gelatin. 

interim results from the APEX study revealed that the stent was well tolerated at 12 months. The most common adverse events were hyphema (a pooling or collection of blood inside the anterior chamber of the eye) lasting more than 30 days (3.8%) and the need for an additional surgery (3.3%).⁹

In a bid to enhance optimisation of the XEN surgical implant, leading opinion leaders in glaucoma management have developed an educational initiative (XEN Expert Principles; XEN EP, Allergan), which highlights three key guiding principles to help surgeons avoid intra-operative events that can make surgery more difficult and/or compromise patient outcomes.

The guidance draws on the collective real-life learnings of its creators, and is born of the culmination of many years of practical experience and a total of over 1,000 eye procedures from three glaucoma experts: Professor Ingeborg Stalmans; Dr Ahmed and Professor Herbert Reitsamer, all of whom have been working with the gel stent from the beginning of its development.

Their purpose is to minimise bleeding (since unnecessary bleeding during the gel stent implantation may negatively impact the procedure); lower conjunctival resistance (proactively lowering conjunctival resistance to outflow increases the likelihood of achieving low and predictable IOP on the first day of surgery); and control inflammation – the primary mediator of fibrosis and bleb failure in glaucoma filtering procedures.

The guiding principles apply not only to the intra-operative phases, but the post-operative stage of stent implantation as well. They include ‘Prep Work’ with guidance on how to optimise the ocular tissues prior to implantation, control inflammation and treat ocular conditions that could negatively impact the surgery; ‘Placement’ – guidance for using the stent injector and how to avoid excess trauma, bleeding and inflammation during the surgery; and ‘Priming’ – assistance on optimising outflow through the device immediately after implantation.

Even if the implant is well positioned, additional action may be required to optimise its function. Post-operative management is also included as supplementary guidance intended for use in conjunction with the existing post-operative management guidance.

“In my opinion,” Dr Ahmed said, “it’s best to ‘start low, stay low’ when it comes to intraocular pressure, as this results in better implantation results for our patients. Placement, priming and preparation are key to obtaining the best possible outcomes with XEN gel stents, too.”

“For instance, it avoids causing trauma to the iris and angle structures with the XEN injector. It’s got power but also has the added benefit of safety – we’re quite happy with the safety of the XEN implant, but could progress it.”

He added: “But what we’ve developed has an excellent pressure target. Looking at other tools, we’ve tried to develop more systematic ways to achieve consistent responses. So, while there are similarities with other procedures, what we wanted was to develop surgical difference in obtaining help to provide that more consistent result.”  

Even with the new guidance, the gel stent implant can only be inserted by surgeons who have received the specialist 1:1 training. The training gives the surgeon theoretical and practical coaching through their first few surgeries and post-operative follow-ups, to ensure they understand all the nuances of the entire process and obtain optimum outcomes.

References

1.     Razeghinejad MR, Spaeth GL. A history of the surgical management of glaucoma Optom Vis Sci. 2011;88;E39-47.

2.     Bull H, von Wolff K, Körber N, Tetz M. Three-year canaloplasty outcomes for the treatment of open-angle glaucoma: European study results. Graefe’s Archive for Clinical and Experimental Ophthalmology. 2011;249:1537-1545.

3.     Nichamin LD. Glaukos iStent trabecular micro-bypass. Middle East African Journal of Ophthalmology. 2009;16;138-140.

4.     Pérez-Torregrosa VT, et al. Combined phacoemulsification and XEN45 surgery from a temporal approach and 2 incisions. Archivos de la Sociedad Española de Oftalmología. 2016; 91;415-421

5.     Dapena CL, Ros RC. Revista Española de Glaucoma e Hipertensión Ocular. 2015.

6.     Allergan Data on File INT/0175/2015 January 2016. Data lock point 13 January 2016.

7.     Glaucoma Research Foundation. FAQ. Available at: https://www.glaucomafoundation.org/info_new.php?id=156&cat=9. Accessed January 2016.

8.     Schlenker M, et al. Efficacy, Safety, and Risk Factors for Failure of Standalone Ab Interno Gelatin Microstent Implantation versus Standalone Trabeculectomy. Ophthalmology. 2017;124;1579-1588

9.     Allergan Data on File INT/0177/2015 January 2016.

Dr Iqbal Ike K. Ahmed, MD, FRCSCE

Dr Ahmed is a glaucoma, cataract and anterior segment surgeon with a practice focus on the surgical management of glaucoma, complex cataract and IOL complications. He holds posts as: assistant professor at the University of Toronto; clinical professor at the University of Utah; fellowship director, Glaucoma & Anterior Segment Surgery (GAASS) Fellowship, University of Toronto; research director at Kensington Eye Institute, University of Toronto; division head, Ophthalmology, Trillium Health Partners, Mississauga ON; medical director, GoEyeCare, Mississauga, Ontario; and co-medical Director, TLC Mississauga. Dr Ahmed consults for numerous pharmaceutical and medical device companies, including Allergan, for which he receives consulting fees, speakers honoraria and research grant/support.