Until nine years ago, glaucoma surgeries were more invasive and more frequently resulted in complications, with longer recovery periods and slower vision improvement. Micro-invasive glaucoma surgeries (MIGS) are being recommended more and more by ophthalmologists earlier in the disease course, due to the technique’s relative safety and its potential for more consistent post-operative recovery.* 

Conventional Pathway MIGS

The primary types of conventional MIGS include:

•     Stenting 
•     Viscodilating 
•     Stripping 
•     Cutting/GATT

Visual recovery is not typically a concern with conventional pathway MIGS. This method is not ideal for all situations, however, cautions Inder Paul Singh, MD, president of The Eye Centers of Racine and Kenosha, Wisconsin, and consultant to Allergan, Bausch + Lomb, and other global pharmaceutical corporations. Some patients need lower target pressures. 

While it can be challenging to reach pressures below the low- to mid-teens, doing so helps avoid hypotony and flat chambers, which are frequent causes of post-operative vision issues.

Additionally, when working with glaucoma patients whose distal channels are collapsed or atrophied, it’s impossible to attain the necessary IOP control through the conventional outflow system.

Trabeculectomy or Tube Shunt Surgery

There are several common causes of post-operative visual acuity changes. These include:

• Hypotony – An IOP of 5 mm Hg or less can adversely affect the cornea and accelerate cataract formation.
• Choroidal Effusions – Abnormal fluid build-up in the suprachoroidal space. 
• Maculopathy – Swelling of the macula, the area of central and fine vision. 
• Ocular Surface Problems – Ocular surface disease (OSD) includes conditions like dry eye, blepharitis, meibomian gland dysfunction, allergic eye diseases, and chemical burns.

Subconjunctival MIGS

When he wants to reach a lower pressure, Dr. Singh says he turns to subconjunctival MIGS, specifically the Xen Gel Stent. This stent uses the same bypass mechanism as trabeculectomy but only creates a 45 μ lumen outflow instead of a large and less consistent hole in the sclera. Less structural deformation of the sclera results in less post-operative risk of temporary eye pressure, which is too low.

Xen’s less invasive nature leads to less inflammation of the anterior chamber and conjunctiva. It also appears to cause less corneal endothelial cell loss than trabeculectomy. 

Because of the high safety profile and rapid visual recovery, Dr. Singh has offered Xen to patients who are resistant to drops, regardless of glaucoma severity. Ultimately, says Singh, Xen achieves low pressures similar to those in traditional subconjunctival surgeries, a predictable post-operative recovery, and fewer office visits. 

This article was reviewed and edited for accuracy by Alan Robin, M.D., a Responsum Health Advisory Council member, ophthalmologist, glaucoma treatment specialist, and leader in the clinical management and scientific study of the disease.

*Singh, I. P. (2021, Sep. 14). The Path to Faster Visual Recovery Following Glaucoma Surgery. Ophthalmology Times. https://www.ophthalmologytimes.com/view/the-path-to-faster-visual-recovery-following-glaucoma-surgery