February 2019

COVER FEATURE

Facing complicated glaucoma cases
Using OVDs in glaucoma surgery


by Ellen Stodola EyeWorld Senior Staff Writer/Digital Editor


Slit lamp photograph of an anterior chamber filled with a cohesive viscoelastic after Ahmed valve placement. There is suspended blood in the anterior chamber.
Source: Nathan Radcliffe, MD



 

Though traditionally used in cataract surgery, viscoelastics are also useful in glaucoma surgery

The use of OVD has evolved from its place in cataract surgery to being useful in glaucoma surgery. Nathan Radcliffe, MD, New York, noted that though he finds viscoelastics to be used frequently in glaucoma surgery, there is not a lot of research or published literature on this. Furthermore, he noted that the on-label use of viscoelastics is for placement in the eye during intraocular surgery (to be removed entirely following the procedure). He added that though viscoelastic use in glaucoma surgery is technically off-label, it can help reform the anterior chamber of the eye if intraocular pressure is low, can tamponade bleeding, and can help prevent low intraocular pressure or hypotony.

How to routinely use OVDs in traditional glaucoma surgery

Dr. Radcliffe first began using viscoelastics in glaucoma surgery when he started implanting the Ahmed Glaucoma Valve (New World Medical, Rancho Cucamonga, California) as a young surgeon. The Ahmed valve has its own intrinsic way of resisting fluid outflow, he said, and the valve is designed to set the pressure to 5 or 6 mm Hg early on in the healing process. However, he found that if you remove all viscoelastic after cataract surgery, the pressure can often be too low in the early postoperative period. “I began completely filling the anterior chamber with cohesive viscoelastic,” he said, adding that he uses ProVisc (sodium hyaluronate, Alcon, Fort Worth, Texas). “You can leave the anterior chamber packed full after an Ahmed valve and you won’t get a pressure spike,” Dr. Radcliffe said. You don’t need to remove the viscoelastic, as it will get filtered out through the valve. “Ironically, filling the eye with a cohesive viscoelastic and placing the patient on oral acetazolamide after Ahmed valve placement can result in a deep chamber that will stay deep for the first few days following surgery, since presumably aqueous production is required to force the viscoelastic to leave the anterior chamber,” he said.
Dr. Radcliffe noted that since he’s adopted the use of viscoelastic in his practice, the need to take patients back to the operating room for procedures such as drain choroidal effusions—a complication when pressure is too low for too long and the choroid swells—has been eliminated.
Meanwhile, Robert Noecker, MD, Fairfield, Connecticut, said that he uses viscoelastics during traditional glaucoma surgery, such as trabeculectomy or EX-PRESS Glaucoma Filtration Device (Alcon), to pressurize the eye. Those surgeries have the highest risk of hypotony or low pressure, he said.
During surgery, viscoelastic helps maintain space and keeps the eye from collapsing, which could be catastrophic and cause a suprachoroidal hemorrhage if the pressure is too low, Dr. Noecker said.
The viscoelastic helps “firm up” the eye and make space when inserting it. “In those surgeries, I also leave it in the eye to keep pressure from going too low,” Dr. Noecker said. He tends to use Healon (sodium hyaluronate, Johnson & Johnson Vision, Santa Ana, California) in these cases, and it will slowly filter out of the eye over a couple of days. The viscoelastic allows for aqueous to flow through, he said, so as long as you have an opening working properly, there’s not a problem.
Dr. Noecker also uses viscoelastic in tube shunts, where he puts it in to begin the case. He likes to put tubes into the sulcus and behind the iris.
If the patient still has the natural lens, Dr. Noecker said he uses it to inflate the angle to make space and keep the eye pressurized during the surgery. If you want to put the tube behind the sulcus, the viscoelastic inflates that space, he said. It can push the iris forward and the lens implant backward. Dr. Noecker said that he tends to leave some of it behind, especially if he has done an Ahmed valve or a tube to prevent the eye pressure from going too low.
Dr. Noecker added that he uses both cohesive and dispersive viscoelastic but tends to use cohesive more. When you are doing MIGS and need to visualize the angle, he thinks the dispersive viscoelastics are a little better at maintaining space and staying in the eye.
Jacob Brubaker, MD, Sacramento, California, agreed, saying that he thinks cohesive viscoelastic has a “bigger niche in the glaucoma world.”
He uses Healon in the anterior chamber when doing a trabeculectomy to maintain the chamber. Dr. Brubaker added that once he’s sutured the flaps, he can evacuate the viscoelastic out of the eye. He generally does not leave viscoelastic in the eye after a trabeculectomy. Healon is good because once you repressurize the eye, the viscoelastic comes out easily, he said.
Dr. Brubaker added the dispersive viscoelastic is good for coating the endothelium of the cornea, which is helpful for cataract surgery. He uses Viscoat (sodium chondroitin sulfate/sodium hyaluronate, Alcon) at the beginning of cataract surgeries.

MIGS and the use of OVDs

In MIGS, viscoelastic is put in when performing gonio surgery, Dr. Radcliffe said. He added that leaving a little behind can be helpful to prevent hyphema. In longer MIGS procedures, Dr. Radcliffe said, it can help to use a more robust cohesive, like Healon 5 or Healon GV (Johnson & Johnson Vision), that will keep the chamber deeper for longer to achieve the surgery. These do a good job maintaining the chamber, he said, but they don’t stop bleeding as well, so you may need to use Viscoat or a dispersive to stop bleeding on the angles. Dr. Radcliffe added that Viscoat can help prevent bleeding after MIGS surgery. He explained that in some cases, for example a patient undergoing trabecular meshwork surgery who is on a blood thinner, he will coat the trabecular meshwork with the dispersive OVD Viscoat prior to filling the rest of the anterior chamber with a cohesive viscoelastic because the dispersive is more effective at tamponading the blood while the cohesive OVD keeps the chamber deep.
Dr. Brubaker said most viscoelastics have predominantly been used in the past to maintain the chamber, and you can use different viscoelastics based on how deep you want your chamber and the stability you need. The big change more recently is using it as a therapeutic treatment as opposed to a temporary maintenance of the chamber.
ABiC (Ellex, Adelaide, Australia), GATT with visco-dilation, and the OMNI Glaucoma Treatment System (Sight Sciences, Menlo Park, California) predominately use cohesive viscoelastic, he said, noting that he uses Healon GV, which has the highest cohesive properties of all the viscoelastics.
When doing MIGS procedures, like the iStent or iStent inject (Glaukos, San Clemente, California), Dr. Noecker said it’s key to have good visualization of the angle. Since this is often done in conjunction with cataract surgery, he likes to put the devices in after the completion of cataract surgery. “I usually use Viscoat because I’ve already used this with cataract surgery,” he said. It helps to inflate the angle and get good visualization, Dr. Noecker added. Pressurizing the eye with viscoelastic will help minimize blood reflex from Schlemm’s canal.
The other role is on the cornea when putting in the gonioscopy lens, Dr. Noecker said, because it helps with the view of the angle and you’ll be less likely to get air bubbles.
The key with the iStent/iStent inject, Dr. Noecker said, is that you have to be able to visualize the trabecular meshwork and Schlemm’s canal.
Dr. Noecker said using viscoelastic with other surgeries, such as with the OMNI and iTrack (Ellex) devices, can be helpful. In these canal-based procedures, viscoelastic is used for visualization and as a therapeutic device to visco-dilate the canal.
Dr. Noecker noted that it may also be useful in endoscopic cyclophotocoagulation (ECP). Viscoelastic can be used for visualization to protect the iris, he said.

Additional thoughts

Dr. Noecker said that viscoelastic can also be a tool to minimize the use of sutures. If someone has hypotony, viscoelastic can be injected postoperatively in the office. If the anterior chamber of the eye is shallow, surgeons can use viscoelastic and inject it in the pre-existing paracentesis site, or they can inject viscoelastic with a needle into the AC to pressurize the eye and protect it.
“I think viscoelastics are a key point of both traditional and MIGS surgeries,” Dr. Noecker said. It’s something he uses on every single case because it can help make the case safer and easier to visualize. “I think we can use it as a tool to minimize the chance of having low pressure during the surgery, as well as postoperatively,” he said.

Editors’ note: Dr. Noecker has financial interests with Allergan (Dublin, Ireland), Alcon, and Ellex. Dr. Brubaker has financial interests with Alcon, Allergan, and New World Medical. Dr. Radcliffe has financial interests with Alcon, Allergan, Ellex, New World Medical, and Sight Sciences.

Contact information

Brubaker
: jacobbrubaker@me.com
Noecker: noeckerrj@gmail.com
Radcliffe: drradcliffe@gmail.com

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