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Patients with moderate, severe glaucoma may benefit from MIGS
The goal in the management of primary open-angle glaucoma is to effectively lower IOP with the least invasive approach. Thus, the micro-invasive glaucoma surgeries are becoming more popular.
Micro-invasive glaucoma surgery (MIGS) promotes a greater safety profile with a quicker recovery while lowering IOP. Many of the MIGS procedures can be combined with cataract surgery to allow for a two-in-one procedure. They use an ab-interno approach that typically allows the conjunctiva to remain intact in case future glaucoma filtration surgeries are needed.
Gretta Ghaner
One specific type of MIGS is the Xen Glaucoma Treatment System (Allergan), which the FDA approved in November 2016. This procedure lowers IOP by draining aqueous humor into the subconjunctival space rather than using the traditional pathways such as the trabecular meshwork or the uveoscleral pathway.
Construction, procedure
The ideal candidate for this procedure is a patient whose glaucoma is still advancing with the maximum topical and surgical therapy.
Michael Cymbor
The Xen Glaucoma Treatment System consists of the Xen 45 gel stent and the disposable Xen injector. The gel stent is 6 mm in length and consists of gelatin cross-linked with glutaraldehyde that is stiff when dehydrated but becomes flexible and conforms to the appropriate space when hydrated by the aqueous humor. This hydration leads to a secure gel stent that has less risk of fibrosis or erosion due to its flexible and inert nature. The cross-linking of the gelatin with the glutaraldehyde inhibits degradation of the stent over time. All of these factors lead to a stable structure of the gel stent that appropriately regulates the flow of aqueous humor.
The Xen 45 gel stent in the superior angle of this patient’s right eye.Source: Michael Cymbor, OD
The Xen 45 gel stent can be seen in the superior nasal subconjunctival space of the patient’s right eye.
The surgical procedure of the Xen Glaucoma Treatment System can be performed with or without cataract surgery. A corneal incision is made where the Xen injector is inserted. The injector goes through the anterior chamber to the targeted angle. The needle, bevel up, goes through the trabecular meshwork and sclera to end up in the subconjunctival space where the gel stent is released. The Xen gel stent lowers IOP by draining aqueous via the subconjunctival space. A bleb is formed as the aqueous drains, and mitomycin C is recommended to prevent scar formation. The bleb is typically lower and more diffuse than with a trabeculectomy. The properly placed Xen gel stent can be visualized in the angle and in the subconjunctiva. Postoperative complications include hyphema, malposition, conjunctival perforation, hypotony and erosion.