In Light of Providing Effective MIGS Management

In Light of Providing Effective MIGS Management

January 06, 2022

MIGS offer IOP lowering by targeting various aspects of normal aqueous dynamics.  The first approaches involve enhancing outflow across the trabecular meshwork and through Schlemm’s canal. 

The juxtacanalicular trabecular meshwork has traditionally been identified as the site of greatest resistance to aqueous outflow.  This resistance can be overcome through bypassing or removing this tissue to lower IOP through increased outflow.

Bypass can be achieved by placing a trabecular meshwork bypass stent which allows aqueous to flow directly through the stent from the anterior chamber into Schlemm’s canal. 

Another approach to bypass the resistance of the trabecular meshwork is goniotomy or trabeculotomy which involves surgical incision and/or excision of this tissue and allows for improved aqueous outflow into Schlemm’s canal.

Dilation of Schlemm’s canal through cannulation and expansion with viscoelastic is yet another approach to improve outflow through the normal physiologic aqueous outflow system

A second group of MIGS approaches seeks to increase outflow via alternate pathways.  The uveoscleral outflow pathway can be augmented by accessing the suprachoroidal space with microstent placement. 

Alternatively, if traditional outflow pathways are unlikely to be improved, aqueous can be shunted into the subconjunctival space through an ab interno, small incision approach.

A third MIGS approach involves decreasing aqueous production by ablation of the ciliary body. 

This approach is employed during endocyclophotocoagulation in which an endoscopic laser probe is inserted through a clear corneal incision and used to directly visualize and ablate the ciliary body. 

Instructions For Patients

Given that the majority of MIGS procedures are performed in conjunction with cataract surgeries, surgeons use the same postoperative instructions as cataract surgery with a few additions:

• Patients can resume their blood thinners the day after the procedure.

• It is recommended to sleep with two pillows for 1 week to prevent microhyphema from pooling in the capsular bag.

• Patients are encouraged to wear a protective shield at night for 1 week to avoid physical pressure on the eye that can lead to inadvertent shallowing of the AC and more hyphema.

Interventional glaucoma, a tailored approach that utilizes up-to-date combinations of medical and surgical therapies in treating all stages of glaucoma, has brought minimally invasive glaucoma surgery (MIGS) to the forefront.

MIGS has increased in popularity because it can help treat mild to moderate glaucoma without causing excessive risks to patients.

While MIGS is generally a safe procedure, understanding how to effectively manage patients’ expectations and surgical outcomes can go a long way toward patient satisfaction.

Preop education

It is crucial to set realistic expectations with the patient prior to surgery. In terms of its IOP lowering effect, we inform patients that the MIGS procedure could potentially help them to stave off one or two of their eyedrops.

However, no matter how successfully a MIGS procedure can reduce intraocular pressure (IOP) to a desirable level, unexpected events during the postoperative period can occur. We usually advise patients that MIGS procedures are safer than traditional glaucoma surgeries like trabeculectomy.

However, transient postop microhyphemas are likely to occur, which can lead to blurry vision for a week or longer. If goniotomy is performed, we strongly recommend patients to stop blood thinners ahead of surgery.

Postoperative exam

For technicians preparing for postop day-1 visits, the most important exam parameters are visual acuity (VA), IOP, anterior chamber (AC) depth, and the amount of red blood cells in the AC. VA can be unpredictable secondary to the amount of hyphema in the AC.

For pseudoexfoliation and pigmentary dispersion glaucoma, there is a greater chance for IOP to be transiently elevated. On subsequent visits, if IOP is low and the AC is shallower than expected, then gonioscopy is needed to check for any hidden clefts.

Medications

Patients often ask our staff what medications to take after the surgery. For mild and moderate glaucoma patients, we usually ask them to stop their glaucoma eyedrops after the procedure.

If IOP is persistently elevated in the postoperative course, then we would put them back on their drops.

For severe glaucoma patients and those with uveitic and steroid response glaucoma with high preop IOP, we ask them to continue their glaucoma eyedrops initially after the surgery, then gradually wean them off their drops if their IOP holds.

Surgeons differ in style, so consult your surgeons on their preference with postop glaucoma drops. In addition, most patients are instructed to use prednisolone acetate 1% (Pred-Forte, Allergan) four times a day with weekly taper.

If they have a history of steroid response, then loteprednol 0.34% (Lotemax SM, Bausch + Lomb) can be given instead.

Other drops to use include non-steroidal anti-inflammatory drugs, or NSAIDs, for 2-4 weeks and an antibiotics drop (typically fluoroquinolone class) for 1 week if intracameral antibiotics were not given.

For a patient undergoing goniotomy, pilocarpine 1% four times a day for 2 weeks is encouraged if tolerated.

Follow-up

Typically, we schedule the patient to return the day after the surgery, 1-2 weeks after, and 4-6 weeks after that.

If both eyes are scheduled sequentially, we typically see the patient 2-4 weeks apart. This is advantageous because the second or third postop visit for the first eye can be checked during the postop visits for the second eye.

This can minimize the number of times that the patient needs to come back.

Triaging potential complications

Understanding the unexpected potential complications of MIGS procedures can help staff be proactive rather than reactive, especially during phone call triage.

Postoperative microhyphema is very typical and can lead to blurry vision. However, hyphema takes time to clear up for some patients. It is important to reassure the patient and have weekly follow-ups.

If hyphema is persistent or progressing with corneal staining and high IOP, your surgeon might perform an anterior chamber washout. When triaging, it is important to look at the IOP from the previous visit.

If initial postop IOP is low but increases a couple of weeks after the procedure, then it is necessary to rule out steroid response as well as closure of the ciliary cleft. If steroid response is suspected, switching from prednisolone to loteprednol is recommended.

A gonioscopic exam can rule out cleft formation. In cases of persistently high IOP lasting more than 1 week after surgery, glaucoma medications would be added.

For chronic angle closure patients who underwent goniosynechialysis with goniotomy but with high IOP, sometimes it is necessary to wait up to 4-6 weeks for their remaining trabecular meshwork to kick in.

Other complications can occur, such as endophthalmitis and macular edema. Since these are not unique to MIGS, consult your surgeons for specific instructions.

XEN specifics

IOP for XEN (Allergan) is usually around single digits in the first week and then rises to mid teens after a few weeks. When IOP is in single digits, patient is advised to avoid strenuous activity and follow head positioning above heart to avoid choroidal hemorrhage or effusion.

During the recovery phase, Tenon encapsulation of the XEN leading to increased IOP can occur. Depending on your surgeon’s comfort level, a slit lamp bleb needling with a bent 30-gauge needle and antifibrotic agents can be done to revitalize the health of the bleb.

MIGS procedures add a new element to the glaucoma treatment algorithm and have continued to gain popularity over the years. With good preparation and clear communication from the staff and doctors, we can make the MIGS experience a pleasant one for our patients.

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