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There are many surgeries that address elevated intraocular pressure and some may be a better option
than others depending on each individual patient. In situations where glaucoma has progressed to a
more severe stage, a drainage device such as a tube shunt may be utilized. Made of a biomedical
material, a tube shunt is implanted into the eye to assist with the drainage of aqueous fluids without
having to utilize the natural drainage system in the eye.
Endoscopic Cyclophotocoagulation (ECP)
Glaucoma is often treated by targeting the natural drainage system of the eye but addressing the
amount of fluid produced inside the eye is another viable treatment option. For patients who have
previously had cataract surgery or are about to undergo cataract surgery, endoscopic
cyclophotocoagulation (ECP) may be an effective treatment for glaucoma. This laser procedure reduces
the amount of fluid that the ciliary body produces inside of the eye, effectively reducing the intraocular
pressure. ECP is often performed during cataract surgery or alongside other MIGS procedures.
Click for indications, candidacy, day of surgery expectations, complications, and for more information on glaucoma comanagement.
At Vance Thompson Vision, we take great care to select the treatment that best suits each individual
patient. Minimally invasive glaucoma surgery, known as MIGS, has changed the way that
ophthalmologists can help manage glaucoma. The multiple MIGS procedures that are available offer
safe and effective ways to better control glaucoma. These procedures help to lower intraocular pressure
by opening or bypassing the natural drainage system of the eye known as the trabecular meshwork.
MIGS are often performed during cataract surgery but can also be performed as a stand-alone
Selective Laser Trabeculoplasty
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Selective Laser Trabeculoplasty is quickly growing in popularity as a first-line treatment for glaucoma.
SLT is a repeatable laser surgery that results in better drainage of the fluid inside the eye. SLT is an
excellent option for a variety of patients with even the mildest glaucoma. This includes patients who
struggle with remembering to take their eye drops, patients who have significant side effects from their
eye drops, and even patients who have never taken eye drops before.
Surgical Planning - So Many MIGS, How Do We Choose?
Since the first minimally invasive glaucoma surgery (MIGS) was introduced in 2012, the world of MIGS has continued to grow offering eye care providers different tools to surgically lower eye pressure (IOP) in patients with glaucoma. While current MIGS are very different, they all aim to accomplish the same goal of utilizing the anterior chamber angle of the eye, helping the conventional aqueous drainage pathway simply work better.
MIGS selection is very patient dependent. Considerations while choosing a MIGS device include severity of glaucoma, IOP, family history/risk for progression, number of IOP lowering drops the patient is currently taking, patient goals regarding those eye drops, and anterior chamber angle anatomy. All MIGS are FDA approved to perform in combination with cataract surgery, but not all MIGS are FDA approved to perform as a standalone procedure. This is considered when selecting one MIGS device over another.
MIGS devices fall into 4 main categories
Trabecular meshwork (TM) bypass – iStent®, iStent inject®, iStent Infinite® (Glaukos Corp) and Hydrus® Microstent (Alcon)
- Trabecular meshwork removal/goniotomy – Kahook Dual Blade (KDB) Glide® (New World Medical) and SION™ (Sight Sciences), TrabEx Pro™ (MicroSurgical Technologies Inc.)
Trabecular meshwork unroofing – OMNI® Surgical System (Sight Sciences) and iTrack™ (NovaEye Medical)
Canaloplasty – OMNI® Surgical System (Sight Sciences), iTrack™ (NovaEye Medical) and Streamline®Surgical System (New World Medical)
Ciliary body ablative Procedures – Endoscopic cyclophotocoagulation (ECP).
Unfortunately, medical insurance companies do play a role in which MIGS device is selected to be used on patients. TM bypass stents (with the exception of iStent Infinite®) can only be used in combination with cataract surgery. Also, insurance coverage for trabecular meshwork stents is only covered if the patient has previously failed topical therapy with IOP lowering eye drops. At the end of 2022, The FDA approved the first micro-invasive implantable device indicated for use as a standalone treatment option for patients with glaucoma – iStent Infinite®. To date, the iStent Infinite® is the newest MIGS device on the market. The iStent Infinite® is similar to the iStent inject® but the difference being 3 stents are implanted instead of 2.
A Quick Review
Trabecular meshwork bypass stents are implanted through the trabecular meshwork into Schlemm’s canal to bypass the area of resistance to aqueous outflow – trabecular meshwork. Since the TM is avascular, most patients experience minimal post-operative inflammation. In the far majority of cases a TM bypass stent post-operative eye will look like a cataract surgery post-operative eye. All iStents® pierce through the TM and reside in Schlemm’s canal. First generation iStent’s® are rarely used since the introduction of iStent Inject® (FDA approved 2018) in which 2 stents are implanted. The Hydrus® Microstent is an 8mm long stent and is also inserted into Schlemm’s canal to scaffold the TM targeting to bypass TM’s aqueous resistance. Stents are typically placed is the nasal quadrant as this is the most accessible portion of the angle to the operating surgeon. All TM bypass stents can be easily visualized with a gonioscopy lens at the slit lamp.
KDB Glide®, SION®, TrabEx Pro™ all remove a couple clock hours of the TM as well as inner wall of Schlemm’s canal. Instead of bypassing the TM with a stent, a portion of the TM is removed completely. TrabEx Pro incorporates irrigation and aspiration for enhanced visualization through-out the procedure. Evidence that a goniotomy has been performed can be visualized with a gonioscopy mirror. Schlemm’s canal is bright white, so a bright white wall can be seen in the nasal angle. Since more cutting is involved with the above procedures, patients may have more cell, RBC’s or a small hyphema may be seen in the immediate post-operative period.
OMNI® and iTrack™ are Migs devices that target the TM, Schlemm’s canal, collector channels, and epi-scleral veins. With both OMNI® and iTrack® a catheter is inserted through the TM, into Schlemm’s canal and can be advanced roughly 360 degrees to inject visco elastic material and dilate the canal, collector channels and epi-scleral veins. When the catheter is removed, the surgeon has the choice to “unroof” or tear through the TM as many clock hours they choose. Since more work is being technically done in the anterior chamber angle with the above devices, patients are slightly more at risk for more cell, RBC and hyphema in the anterior chamber angle in the immediate post-operative period.
Streamline® Surgical System is like OMNI and iTrack in that it uses visco elastic material to dilate Schlemm’s canal, collector channels and episcleral veins. Instead of using a catheter to deliver visco elastic it instead punches a hole through the TM and injects visco elastic straight into Sclemm’s canal. Multiple injections into the canal can be made. Post-operatively majority of patients have minimal inflammation but it is also not uncommon to have increased cell and a mild hyphema present in the AC.
ECP is a cyclo-destructive procedure in which an endoscopic laser is used to target ciliary body aqueous secreting epithelial cells to reduce the production of aqueous. ECP is rarely used as a standalone procedure but more commonly combined with other MIGS devices above. More inflammation is usually seen in these eye’s post-operatively in which a steroid is used QID for 1 week then BID for 3 more weeks.
Choosing a MIGS device for a patient with glaucoma is very patient dependent and many factors come into play. In General, stents are used in the mild to moderate glaucoma’s. TM removal and canaloplasty’s are used in the more moderate to severe glaucoma’s. Medication burden and ocular surface disease play a large role in MIGS selection as well. If a patient with mild glaucoma is taking multiple eye-drops and wishes to get off them, TM removal or canaloplasty might be chosen. ECP is generally tagged along with TM removal or canaloplasty MIGS in moderate to severe glaucoma’s to gain an addition point or two in IOP reduction. Each point matters, for each additional point IOP is lowered glaucoma progression decreases by 10%.
Why the Hyphema?
It is not uncommon to see a hyphema in the anterior chamber in the immediate post-operative period after a MIGS procedure. A hyphema occurs due to backflow of blood from the epi-sceral veins into the anterior chamber. This is not a concern and typically resolves within a couple days.
How do we measure success?
MIGS success should not only be measured by IOP lowering but also in the reduction of IOP lowering meds. The higher the pre-operative IOP the greater the IOP point reduction will be.
In summary, we are lucky to practice at a time where eye care providers have multiple different surgical devices to choose from to fight the battle against glaucoma. Continued research is being done on new MIGS devices to provide safe and efficacious alternatives to invasive filtering glaucoma surgeries.