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Glaucoma Surgeries – What Are Your Treatment Options

There are now multiple glaucoma treatment options that can be performed to lower intraocular pressure and prevent further vision loss. Which option is most appropriate for you will depend on the severity of your glaucoma and the comfort of your surgeon with the available glaucoma treatment options.

Glaucoma Surgery Categories

There are a number of different types of surgeries and techniques, which can be split into (roughly) three using this categorical criteria.

  1. Non-invasive (i.e. laser)
  2. Minimally invasive – a whole new type of glaucoma surgery (i.e. Canaloplasty)
  3. Penetrating or the standard glaucoma surgery (i.e. Trabeculectomy and glaucoma drainage devices)

Clearly, of those three most people would prefer to avoid that last one.

We can also think of glaucoma surgery in terms of a MNEMONIC – SEA

  1. Shunts, which is essentially creating a non-physiologic pathway from the anterior chamber into usually subconjuctival space but it could be something else too.
  2. Enhance, which is to take the natural pathway of anterior chamber through the trabecular meshwork into Schlemm’s canal and then out the collector channel system into the venous system.
  3. Ablate. Destroy.

Laser Treatments for Glaucoma

A laser treatment for narrow and closed angle glaucoma. A hole is created on the Iris allowing fluid through and out the natural drainage system. This treatment eliminates pupillary block.

A laser treatment for Plauteau Iris Glaucoma. It’s “Plasty”, so instead of making a hole you’re basically shrinking the Iris to pull it away from the angle. When Iridotomy doesn’t work in plateau iris, you then do an Iridoplasty.

Laser Trabeculoplasty

Laser Trabeculoplasty can be split up into Argon (ALT), Selective (SLT) and Micropulse (MLT) Laser Trabeculoplasty.

Argon Laser Trabeculoplasty (ALT)

The Argon Laser Trabeculoplasty or ALT has been around for a very, very long time.  It works well for open-angle glaucoma. It can be performed in one to two sessions but the problem is it does still result in microscopic scars and also may limit future surgeries. So surgeries that involved opening up that Schlemm’s canal, can actually be problematic because the scars essentially seal the canal, so surgery such as Canaloplasty and potentially some of the newer surgeries that are not yet available could be limited by Argon Laser Trabeculoplasty.

Selective Laser Trabeculoplasty (SLT)

More recently in the 1990s, Doctor Latina developed Selective Laser Trabeculoplasty. SLT uses a “Q-switched, frequency-doubled Nd:YAG laser”. This laser energy is preferentially absorbed by the pigment-containing cells in the trabecular meshwork while cells without pigment are left undamaged. Because SLT does not “coagulate” (or melt) tissue this results in a less traumatic laser treatment compared to ALT. And because it doesn’t cause any damage it can actually be repeated. So it works about seventy percent of the time. Works about as well as a drop, which is also about as well as Argon Laser Trabeculoplasty work so it’s not really any better in terms of how of effective it is but it’s its repeatable and it doesn’t close future doors.

Micropulse® Laser Trabeculoplasty (MLT)

Micropulse Diode Laser Trabeculoplasty (MDLT or MLT) is the latest addition to the Laser Trabeculoplasty party. MLT works by using very short bursts of the laser (called “micro-pulses”) to heat up the trabecular meshwork cells without destroying them. This avoids the damage and scarring associated with ALT while minimizing the inflammation and post-operative IOP elevations seen with both ALT and SLT. Basically this is a newer and cheaper version of SLT, seems to work as well as SLT and so there’s some benefits to having this.

Laser Cyclophotocoagulation For Glaucoma

Unlike other glaucoma treatments that work by making it easier for fluid to leave the eye, Cyclophotogoagulation works by decreasing the production of aqueous fluid. Aqueous fluid is produced by finger-like projections of tissue hidden behind the iris. These are called the ciliary processes. If these ciliary processes are damaged (cyclodestruction) then less fluid is produced. Less fluid production should result in a lower eye pressure (IOP).

Transscleral Cyclophotocoagulation (TCP)

Earlier attempts at cyclodestruction were, for the most part, done by placing a laser probe on the surface of the eye. This technique was called Transscleral Cyclophotocoagulation (TCP) as the laser beam had to focus through the wall of the eye (sclera) in order to reach the ciliary body. Because the sclera is opaque the surgeon could not actually see the ciliary processes being destroyed. It’s likely that many other tissues in the eye were also being damaged using TCP. It’s also believed that this “collateral damage” was the reason for both the unpredictable IOP lowering and the high complication rate.

Endoscopic Cyclophotocoagulation (ECP)

One of the first things most surgeons are taught is the importance of visualizing the structures being worked upon. After all, if you can’t see it, how do you know you are cutting, suturing, or coagulating (melting) the correct tissue? With Transcleral Cyclophotocoagulation (TCP) the surgeon didn’t know. Fortunately, there is now a method of treating the ciliary body processes which uses a tiny endoscope to visualize the area being treated. With this technology the surgeon can view the magnified image of the ciliary processes on a video monitor before choosing which areas and for how long to treat. The Endo Optiks endoscope used for ECP is essentially a tube that includes a lens, a fiber optic cable,  a light source and two lasers (one for aiming and one to treat). All of this in a tube no larger than a large hypodermic needle!

Endocyclophotocoagulation (ECP), appears to be a much safer option than TCP but with only a modest (or at least somewhat unpredictable) IOP lowering benefit. The real issue with ECP is that there aren’t that many studies out so we really don’t know how well it works. However, ECP is one of many glaucoma treatment options (including canaloplasty and MIGS) that are reasonable to consider having at the time of cataract surgery.

MicroPulse® P3 “Cyclophotocoagulation”

Traditional methods of cyclophotocoagulation burn the ciliary body. MicroPulse® P3 “Cyclophotocoagulation”, however, uses a slow application of laser energy that is “chopped” into micropulses (or, bursts). Each pulse heats up, but does not burn or destroy eye tissue. In between each pulse is a pause. This pause allows the eye tissue to cool off. In this manner the eye tissue is changed rather than destroyed. Because it does not burn or destroy tissue it should not cause significant inflammation.

Although there can be some discomfort during the laser application, the procedure is generally not painful. However, unlike other glaucoma laser procedures (such as laser trabeculoplasty), MP3 requires more than just topical anesthetic drops in order to minimize discomfort. Either a local anesthetic “block” (injection around the eye) or intravenous (IV) sedation can be used to achieve adequate comfort during the procedure.

Incisional Glaucoma Surgeries

These are what we can basically split into Penetrating (the more traditional ones) and the Lower Risk Surgeries, which are called “Minimally Invasive Glaucoma Surgeries” or “Micro Invasive Glaucoma Surgeries”—basically MIGS.

 

Traditional “Penetrating”  Glaucoma Surgery

Trabeculectomy Glaucoma Surgery  

Trabeculectomy is traditionally offered to patients who have failed drops, failed SLT, and they’re advancing their glaucoma. Traditionally the glaucoma has to be pretty severe – at least moderate to severe. Trabeculectomy isn’t offered to somebody with mild glaucoma or just ocular hypertension because Trabeculectomy – there’s no other way to say it, pretty barbaric: You’re creating a fistula in the eye.

The oldest of modern glaucoma surgeries, trabeculectomy rapidly decreases intraocular pressure by punching a hole in the eye. A flap is left in place in order to control the amount of fluid that percolates under the thin surface layer of tissue (called the “bleb”).

Due to the invasive nature of the procedure, there is the danger of severe bleeding, bleb failure due to sudden decompression post operatively as well as formation of scar tissue. Moreover, trabeculectomy places the eye at increased lifetime risk for infection. 

Glaucoma Drainage Devices for Glaucoma

Also known as aqueous shunts or drainage implants, these plate-shaped devices must be sutured onto the surface of the eye beneath the conjunctiva. The hollow tube which connects to the plate is either inserted through the cornea or sclera at the time of initial surgery or at a later date. Once the tube has been properly inserted these implants function by draining fluid from the inside of the eye into a reservoir around the plate and underneath the conjunctiva. The device acts like a garden hose that continuously drains excess fluid out. Generally, this surgery can achieve IOPs in the mid-teens. However the rapid egress of fluid also poses a risk of a condition called hypotony (dangerously low IOP) which can lead to loss of vision. Newer models like the Ahmed shunt possess a valve which provides better control of the drain’s flow rate. However,  as  with  all  body  implants,  there  are  the  risks  associated  with  movement  of the  implant, infection,  as  well  as  scarring that could result in double vision. 

Minimally Invasive Glaucoma Surgery (MIGS) or
Lower Risks Incisional Glaucoma Surgeries

Canaloplasty

Ab-Externo Canaloplasty

Canaloplasty uses a micro-catheter to open the eye’s natural drainage system (“Schlemm’s canal”). This canal is then opened using a sterile, gel-like material (“viscoelastic”). The iTrack® micro-catheter is then removed while a suture is threaded through Schlemm’s canal. The suture is then tied down resulting in tension on the inner wall of the canal – just as you might pull on the strings of a “hoodie” to close the hood over your face. The suture placed in the eye’s drainage canal can keep the canal stretched open for years. Once this canal is opened, the eye’s fluid can exit through a more natural process allowing the pressure in the eye to drop to a more normal level.

  • It uses the eye’s natural drainage system
  • It is a “non-penetrating” procedure that does not create a permanent fistula in the wall of the eye
  • It does not require a bleb (a blister-like fluid collection)
  • Provides long-term reduction in IOP (see three year results below)
  • Reduces the need for medications to keep the IOP controlled
  • Is a good option for those patients who are not yet ready for more trabeculectomy or tube shunts
  • Is safer than traditional glaucoma surgeries (Canaloplasty vs Trabeculectomy)

Ab-Interno Canaloplasty (ABiC)

Whereas, with traditional Canaloplasty, the Micro-catheter is inserted from an external approach: cutting through the conjuctiva and sclera, with Ab-Interno Canaloplasty, the Micro-catheter is inserted from an internal approach: through either a clear corneal or a limbal micro-incision, then through a small opening in the Trabecular Meshwork, and into the Schlemm’s canal. With Ab-Interno, the eye tissue is preserved and not cut – no more flaps!

  • Similar benefits as traditional canaloplasty
  • Similar IOP-lowering as tried and true traditional Canaloplasty.
  • Restoration of the eye’s natural drainage channels.
  • No permanent placement of foreign body – prolene suture, stents or implants, in the eye!
  • Future surgery is not compromised
  • Easier and quicker 15 minutes Procedure!
  • Preserves tissue. No deep cuts or creation of flaps needed!
  • Potentially offer better clinical outcomes than any other currently available MIGS procedure.  

Trabeculotomy for Glaucoma

To perform a trabeculotomy is to create an opening in the trabecular meshwork.

Micro-invasive Suture Trabeculotomy (MIST)

What else can we do? Well one thing we can do is dilate the canal, the other thing we can do is say, “well, if trabecular meshwork is the primary area of restriction, why don’t we just rip it out or tear it open?” And so, we can do that. It turns out that if you’ve had a patient who’s had Ab-externo Canaloplasty and at some point the pressure is no longer controlled— if they’ve had the Stent — so, if they’ve had the suture placed in the canal, you can go in with micro-forceps or another instrument and pull the suture through. Pulling the suture through rips open the Trabecular meshwork— that’s called Micro-invasive Suture Trabeculotomy. And in a two year study it showed a 45% reduction in intraocular pressure. So, low-risk procedure.

Basically, the main risk you have is hyphema (system bleeding in the front of the eye as you open up the trabecular meshwork). That generally goes away on its own. There’s very low risk with any of these angle procedures of cyclodialysis, which can result in hypotony. That’s pretty low risk. So you know the nice thing about canaloplasty is that you can potentially get a double benefit: you can get the initial opening of the canal and then if you need to you can you know pull the suture through the trabecular meshwork.

Gonioscopy-Assisted Transluminal Trabeculotomy (GATT)

So, there’s also if you’ve got somebody who has not had Canaloplasty you can perform what’s called Gonioscopy-Assisted Transluminal Trabeculotomy. That’s essentially taking that catheter we saw before but instead of just dilating the canal you move the catheter or some people will use an aid…a suture if you want to (you know) get really cheap you don’t want to use an instrument that’s been designed for this it can be done it’s a bit more challenging but in any case you move the suture around the canal and then you take the two end of the suture and you pull through and you rip through the trabecular meshwork. And it also shows a pressure reduction around 40% at two years.

Ab-Interno Trabeculotomy

Ab-Interno Trabeculotomy uses a device called a Trabectome, which has to be done with or after cataract surgery. As with all of the Trabeculotomies, they do limit the potential for future canal-based surgeries . Essentially, it’s got these electrodes that produce plasma and then it sucks up the trabecular meshwork tissue as it opens up the canal—permanently ablating a portion of the trabecular meshwork and inner wall of Schlemm canal to increase aqueous outflow. Ab-Interno Trabeculotomy is a more expensive and less popular option. 

Kahook Dual Blade Trabeculotomy

And one of the more interesting, less expensive options is the Kahook Dual Blade. Basically, it’s like a poor man’s Trabectome. But instead of using a plasma blade, it’s got this neat (I’ll show you) this really neat, design of this blade. There we go… that allows you to safely remove the trabecular meshwork as kind of a strip. So it strips it off. And here you can see the tip of the blade there and it’s got a kind of foot plate and then these two side blades, so you get a sharp tip to get into the trabecular meshwork. And boy, don’t I wish the trabecular meshwork looked that clear and easy to find. Angle base surgery is technically challenging. There’s a high learning curve but once you’ve got it, it can be quite fast and really gentle in terms of the patient experience. 

iStent

The iStent is the first FDA approved “trabecular microbypass device.” It is a 1.0mm long snorkel-like device made out of medical grade titanium. The long end of the snorkel is tapered. Using a specially designed inserter, the surgeon presses the tapered end through the trabecular meshwork and lodges it into the canal of Schlemm. This allows aqueous fluid to flow out of the anterior chamber directly into Schlemm’s canal.

If you happen to have ocular hypertension or mild glaucoma that is well-controlled on one or two drops and your cataract is ready to be surgically removed and your insurance covers placement of an iStent or you happen to be obscenely wealthy and just like the idea of having a piece of microscopic titanium eye jewelry then this might be a reasonable option for you to consider. If, on the other hand, your glaucoma is moderate or severe, poorly controlled, your insurance doesn’t cover placement of an iStent, or you are likely to need additional glaucoma surgery in the future, then the iStent is likely to disappoint.

One problem with iStent is that it limits future surgeries. If you do this you can’t do canaloplasty or other procedures that require access to that area of the canal. 

The question is, “do they work?” Maybe not so impressive when you’re looking at the difference between cataract surgery alone and cataract surgery plus the iStent® but taking a bigger picture it can be a useful option.   

CyPass® Micro-Stent Glaucoma Device

The CyPass® Micro-Stent  got its FDA approval at the end of 2016.  This glaucoma device uses an outflow shunting method that has not been available to us before. That is, it’s also like with the iStent®, only approved for those who are also having cataract surgery. The nice thing about this is because it uses a separate outflow it can be used even in patients who have had or may need to have other glaucoma surgeries. Top concern for this device the choice of material for this stent: polyimide. Polyimide is known to become brittle with time when exposed to heat and humidity. Far from being cold and dry, the suprachoroidal space in which the CyPass® is implanted is both warm and humid. Hence, there’s a possibility that the stent is susceptible to shattering inside the eye leading to complications such as the dreaded Uveitis Glaucoma Hyphema syndrome (UGH). In the spirit of “primum non nocere” (above all, do not harm) It would seem prudent to reflect on whether this is really the best glaucoma surgical implant to use. 

Xen® 45 Gel Stent

The Xen® 45 Gel Stent is a chemically treated gelatin tube that has been designed so that the aqueous flow through it is restricted in such a way that it reduces the risk of hypotony. This is essentially an Ab-Interno method of trabeculectomy—you’re shunting the fluid into the subconjunctival space. It still requires a bleb to achieve intraocular pressure lowering and as such it still has all of the potential complications or most if not all, that trabeculectomy would.

The issue with this is that although it shares many of the complications with Trabeculectomy and although it’s much faster and in some ways easier to do, it doesn’t seem to do quite as well as Trabeculectomy in terms of pressure reduction.

Cataract Surgery

Cataract surgery alone can be effective in patients with mild to moderate glaucoma or those that are not yet on max-tolerated medical therapy. In patients who are on max-tolerated medical therapy and need cataract surgery, combined cataract surgery and a MIGS procedure, is reasonable.  

What’s In the Pipeline?

iStent Supra® Suprachoroidal Micro-Bypass Stent

This is designed to reduce IOP in mild-to-moderate Open Angle Glaucoma patients undergoing cataract surgery. The iStent Supra® is a 4mm (less than one quarter inch long) tube with a hole at each end. Made of Polyethersulfone (PES) and titanium, it is intended to be placed in the supraciliary space (next to the uvea). Aqueous fluid should then be able to flow through this tube, out the small holes, and into the uveoscleral space. It can be implanted alone or at the time of cataract surgery through a very small incision. 

This device is approved for marketing in the European Union and certain other countries outside the United States .

Latest News on iStent Supra®| February 16, 2017 [Source]:

Glaukos Completes Patient Enrollment in Pivotal Phase of U.S. IDE Clinical Trial for iStent SUPRA® [Source]

HydrusMicrostent 

The Hydrus™ Microstent (Ivantis, Irvine, CA), like the iStent, is a trabecular microbypass stent. Made of nickel-titanium, it can most easily be thought of as a very long iStent.  Whereas the iStent is only 1.0mm long, the Hydrus™ microstent is about as long as an eyelash.

The Hydrus™ Microstent is intended to be placed in Schlemm’s canal. As with the iStent, it directs fluid across the trabecular meshwork and into the Schlemm’s canal. In addition, however, the Hydrus™ Microstent also works as a scaffolding device which keeps a portion of Schlemm’s canal open.

As with the iStent, the Hydrus™ implant is intended to be combined with cataract surgery.  Unlike the iStent, however, initial results obtained two years after surgery appear to be promising.

Latest News on Hydrus™ Microstent | October 31, 2017

Ivantis Completes Pre-Market Approval Submission for the Hydrus™ Microstent for Minimally Invasive Glaucoma Surgery (MIGS) [Source]

InnFocus MicroShunt®

The InnFocus MicroShunt® is essentially— it’s an Ab-externo, unfortunately. It’s essentially a controlled trabeculectomy. So instead of creating a flap and punching a hole, you essentially place this device that limits flow. This device is very much like the FDA-approved XEN® Gel Stent, which you could do from inside the eye. This is similar but requires that you come from the outside of the eyes.  

Latest News on the InnFocus MicroShunt®| March 8, 2017

InnFocus MicroShunt with MMC reduces IOP in 4-year series [Source]

Stegmann Canal Expander

The inventor of canaloplasty, Dr. Robert Stegmann has invented is a tube-shaped scaffolding device, about twice the thickness of a human hair. It is placed into Schlemm’s canal after canaloplasty has been performed. Once inserted, the Stegmann Canal Expander® keeps up to half of the canal open – permanently.   

The results of a 2-year study evaluating canaloplasty with the Stegmann Canal Expander® on patients with moderate to advanced glaucoma show that the average IOP lowered by 50% and the  average number of glaucoma medications required dropped from just under three (2.8) to essentially none (0.2).  Over 90% of patients in this study were drop-free two years after Canaloplasty with the Stegmann Canal Expander®

It appears that Canaloplasty with the Stegmann Canal Expander® is as effective as trabeculectomy at lowering IOP. 

Latest News on Stegmann Canal Expander| August 2017

Canaloplasty with Stegmann Canal Expander for primary open-angle glaucoma: two-year clinical results. [Source]

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