Perspective

Patients with moderate, severe glaucoma may benefit from MIGS

The Xen gel stent has been shown to reduce IOP and the number of medications in this group.

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.

Clinical studies

Case report: Octopus 24-2 visual field completed prior to cataract surgery. The patient had grade 3 nuclear sclerosis in both eyes that were visually significant. Nasal defects can be noted in the right eye greater than the left. The left eye also revealed a greater superior arcuate defect consistent with POAG. Serial visual fields are warranted to note change post-cataract surgery.

In a clinical trial performed by Allergan, baseline mean IOP was 25.1 (±3.7) mm Hg with the usage of 3.5 (±1.0) hypotensive medications. After 12 months, the mean IOP was 15.9 (±5.2) mm Hg, with the subjects using a mean of 1.7 (±1.5) hypotensive medications with no serious adverse reactions. However, 32.3% of the subjects required bleb needling, mostly due to fibrosis of the bleb (18.5%).

Another study was performed evaluating Xen gel stent implantation in conjunction with cataract surgery (Sheybani). Patients in the study had a mean baseline IOP of 20.8 (± 4.6) mm Hg and used 2.7 (±1.0) hypotensive medications. At 12 months, the mean IOP was 13.1 (±3.6) mm Hg, 0.9 (±1.1) hypotensive medications were used, and there were no significant ocular complications.

Case presentation

A 76-year-old male with primary open-angle glaucoma (POAG) presented for a glaucoma follow-up evaluation. The patient had previous argon laser trabeculoplasty in both eyes. The patient was using brimonidine three times a day, dorzolamide three times a day and pilocarpine three times a day. His IOPs were in the thirties, with POAG progression.

The Octopus G-TOP (Haag Streit) perimetry revealed nasal steps in both eyes, with the right eye being more significant as well as having a superior arcuate defect. Using the Hodapp, Parish and Anderson classification system, both visual fields have a mean deviation of less than -6 dB, which would be considered an early defect. However, both involve the central 5° of fixation, thus should be graded as moderate field defects in both eyes.

OCT of optic nerve head and ganglion cell complex in both eyes of the same patient. Note severe thinning of the superior and inferior temporal optic nerve head with ganglion cell loss in both eyes. The FLV and global loss volume GLV are flagged in this patient.

The Optovue OCT provided evidence of thinning of the superior and inferior temporal areas of the nerve fiber layer. The OCT also displayed significant ganglion cell complex thinning in the right eye greater than the left. The focal loss volume (FLV) and global loss volume (GLV) are flagged in this patient. Based on these test results, it can be determined that this patient has moderate to severe POAG in the right eye and moderate POAG in the left eye. Lowering of the patient’s IOP is a priority to prevent progression of this disease.

The next step in the treatment of the POAG was phacoemulsification with intraocular lens implantation in combination with Kahook Dual Blade (KDB) goniotomy. This was performed in both eyes in 2017. The IOP lowered to the mid-to-high twenties in both eyes after cataract surgery but was not enough of a pressure reduction considering the severity of the patient’s glaucoma.

Xen was performed on his right eye first, and at the 1-day postoperative visit his IOP was 8 mm Hg OD, and at the 1-week visit his IOP was 15 mm Hg OD. This is a significant decrease in IOP compared to the cataract surgery and KDB goniotomy. The left eye will undergo the Xen procedure in the near future.

Xen in particular is a MIGS that targets patients with moderate to severe glaucoma. The Xen 45 gel stent is designed to accurately regulate the flow of aqueous with its hydrophilic nature. In multiple studies, the Xen gel stent proved to be effective at lowering IOP with less risk of significant side effects (Lavin et al., Fea, Pfeiffer et al.). With all of this in mind, Xen is an important MIGS in 2018.

Disclosures: Cymbor is a speaker for Optovue and has received unrestricted research grants from Optovue, Heidelberg and Zeiss. Ghaner reports no relevant financial disclosures.

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.

PAGE BREAK

Clinical studies

Case report: Octopus 24-2 visual field completed prior to cataract surgery. The patient had grade 3 nuclear sclerosis in both eyes that were visually significant. Nasal defects can be noted in the right eye greater than the left. The left eye also revealed a greater superior arcuate defect consistent with POAG. Serial visual fields are warranted to note change post-cataract surgery.

In a clinical trial performed by Allergan, baseline mean IOP was 25.1 (±3.7) mm Hg with the usage of 3.5 (±1.0) hypotensive medications. After 12 months, the mean IOP was 15.9 (±5.2) mm Hg, with the subjects using a mean of 1.7 (±1.5) hypotensive medications with no serious adverse reactions. However, 32.3% of the subjects required bleb needling, mostly due to fibrosis of the bleb (18.5%).

Another study was performed evaluating Xen gel stent implantation in conjunction with cataract surgery (Sheybani). Patients in the study had a mean baseline IOP of 20.8 (± 4.6) mm Hg and used 2.7 (±1.0) hypotensive medications. At 12 months, the mean IOP was 13.1 (±3.6) mm Hg, 0.9 (±1.1) hypotensive medications were used, and there were no significant ocular complications.

Case presentation

A 76-year-old male with primary open-angle glaucoma (POAG) presented for a glaucoma follow-up evaluation. The patient had previous argon laser trabeculoplasty in both eyes. The patient was using brimonidine three times a day, dorzolamide three times a day and pilocarpine three times a day. His IOPs were in the thirties, with POAG progression.

The Octopus G-TOP (Haag Streit) perimetry revealed nasal steps in both eyes, with the right eye being more significant as well as having a superior arcuate defect. Using the Hodapp, Parish and Anderson classification system, both visual fields have a mean deviation of less than -6 dB, which would be considered an early defect. However, both involve the central 5° of fixation, thus should be graded as moderate field defects in both eyes.

OCT of optic nerve head and ganglion cell complex in both eyes of the same patient. Note severe thinning of the superior and inferior temporal optic nerve head with ganglion cell loss in both eyes. The FLV and global loss volume GLV are flagged in this patient.

The Optovue OCT provided evidence of thinning of the superior and inferior temporal areas of the nerve fiber layer. The OCT also displayed significant ganglion cell complex thinning in the right eye greater than the left. The focal loss volume (FLV) and global loss volume (GLV) are flagged in this patient. Based on these test results, it can be determined that this patient has moderate to severe POAG in the right eye and moderate POAG in the left eye. Lowering of the patient’s IOP is a priority to prevent progression of this disease.

PAGE BREAK

The next step in the treatment of the POAG was phacoemulsification with intraocular lens implantation in combination with Kahook Dual Blade (KDB) goniotomy. This was performed in both eyes in 2017. The IOP lowered to the mid-to-high twenties in both eyes after cataract surgery but was not enough of a pressure reduction considering the severity of the patient’s glaucoma.

Xen was performed on his right eye first, and at the 1-day postoperative visit his IOP was 8 mm Hg OD, and at the 1-week visit his IOP was 15 mm Hg OD. This is a significant decrease in IOP compared to the cataract surgery and KDB goniotomy. The left eye will undergo the Xen procedure in the near future.

Xen in particular is a MIGS that targets patients with moderate to severe glaucoma. The Xen 45 gel stent is designed to accurately regulate the flow of aqueous with its hydrophilic nature. In multiple studies, the Xen gel stent proved to be effective at lowering IOP with less risk of significant side effects (Lavin et al., Fea, Pfeiffer et al.). With all of this in mind, Xen is an important MIGS in 2018.

Disclosures: Cymbor is a speaker for Optovue and has received unrestricted research grants from Optovue, Heidelberg and Zeiss. Ghaner reports no relevant financial disclosures.

    Perspective
    Justin Schweitzer

    Justin Schweitzer

    A number of other procedures can be performed in the trabecular meshwork, Schlemm’s canal and suprachoroidal space to reduce IOP.

    The iStent (Glaukos) is a trabecular meshwork bypass stent designed to serve as a bypass through the trabecular meshwork facilitating aqueous flow into Schlemm’s canal.

    The iStent Inject (Glaukos) is a trabecular meshwork bypass stent based on the same fluidic method of action as the iStent. The device is designed to facilitate outflow of aqueous humor by creating two bypasses through the trabecular meshwork with two preloaded stents.

    Ab interno canaloplasty (Ellex) uses an illuminated, micron-scale microcatheter designed to viscodilate 360 degrees of Schlemm’s canal.

    Visco360 (Sight Sciences) uses an advanceable microcatheter to deliver controlled amounts of viscoelastic fluid to viscodilate 360 degrees of Schlemm’s canal.

    With gonioscopy-assisted transluminal trabeculotomy, a goniotomy is created, and a suture or microcatheter is navigated through 360 degrees of Schlemm’s canal. The suture or microcatheter is then pulled through to unroof the trabecular meshwork.

    OMNI (Sight Sciences) uses a microcatheter to viscodilate 360 degrees of Schlemm’s canal and unroofs up to 360 degrees of the trabecular meshwork.

    The Kahook Dual Blade (New World Medical) removes 3 to 5 clock hours of trabecular meshwork and the inner wall of Schlemm’s canal to allow unimpeded aqueous outflow.

    Trabectome (Neomedix) involves ablating 120 to 180 degrees of the trabecular meshwork and inner wall of Schlemm’s canal.

    The Cypass Micro-Stent (Alcon) is designed to access the supraciliary space. The device bypasses the conventional outflow pathway and targets the uveoscleral outflow pathway.

    The iStent, iStent Inject and Cypass all are done in conjunction with cataract surgery. All other procedures can be performed alone or in conjunction with cataract surgery.

    • Justin Schweitzer, OD, FAAO
    • Vance Thompson Vision, Sioux Falls, S.D., and Fargo, N.D.

    Disclosures: Schweitzer reports he is a consultant for Alcon, Allergan and Glaukos.