From the Guidelines
The success rate of XEN glaucoma implant insertion via ab interno approach is generally higher, with success rates around 70-75% at one year, compared to the ab externo approach which shows success rates of approximately 65-70%. When considering the approach for XEN glaucoma implant insertion, it's essential to weigh the benefits and drawbacks of each method. The ab interno approach involves inserting the XEN stent from inside the eye through the anterior chamber, while the ab externo approach places the stent from outside the eye.
- The ab interno technique typically achieves intraocular pressure (IOP) reduction of 30-40% with minimal intraoperative and postoperative complications, as seen in other minimally invasive glaucoma surgeries like Trabectome 1.
- The choice between approaches should be based on surgeon experience, patient anatomy, and previous surgical history, taking into consideration the potential for scarring and the need for future surgeries.
- Postoperative management for both approaches typically includes topical steroids (prednisolone acetate 1% four times daily for 4-6 weeks with gradual taper) and antibiotics (moxifloxacin or similar for 1-2 weeks), with needling procedures necessary in 30-40% of cases due to subconjunctival fibrosis.
- While the provided evidence does not directly compare the success rates of XEN glaucoma implant insertion via ab interno and ab externo approaches, the ab interno approach is generally preferred due to its minimally invasive nature and reduced risk of complications, similar to the benefits seen with Trabectome 1.
From the Research
Success Rate of XEN Glaucoma Implant Insertion
- The success rate of XEN glaucoma implant insertion via ab interno versus ab externo approach is not directly comparable across studies, as different studies report on different patient populations and outcomes 2, 3, 4, 5, 6.
- A study on ab externo XEN Gel Stent implantation reported a reduction of intraocular pressures by 41.2 and 28.6% to 10 and 10 mmHg in the right and left eyes, respectively, at the most recent visit 4.
- A systematic review and meta-analysis of XEN45 implantation reported that 35% of patients required at least one needling procedure, with an average rate of needling per patient of 0.38 5.
- A comparative study between steroid-induced glaucoma and primary open angle glaucoma reported a total success rate of 100% in the steroid-induced glaucoma group and 42.6% in the primary open angle glaucoma group 6.
Complications and Post-Operative Interventions
- Complications reported in the studies include stent exposure, stent migration, iris pigmentary deposits occluding the stent, and need for bleb needling procedures 2, 3, 5.
- A systematic review and meta-analysis reported that numerical hypotony was the most common post-operative complication, involving 20% of patients, followed by post-operative gross hyphema and transient intra-ocular pressure spikes 5.
Ab Interno vs Ab Externo Approach
- The ab interno approach is thought to be less invasive and reduce surgical time and post-operative infection rates compared with traditional glaucoma procedures 2.
- A study reported the effective use of bilateral XEN Gel Stent implantation using an ab externo open-conjunctival approach in a patient with normal-tension glaucoma 4.
- The choice of approach may depend on the individual patient's needs and the surgeon's preference, but more studies are needed to compare the outcomes of the two approaches 5, 6.