LOUIS B. CANTOR, MD
Ophthalmic viscosurgical devices (OVDs) play a critical
role in my glaucoma filtering procedures. During a
trabeculectomy, I prefer to permit steady leakage from
the sclerotomy site and generally place only two sutures
in the scleral flap. In order to prevent an early shallow
anterior chamber or hypotony (Figure 1), I therefore
inject a high-molecular-weight OVD (Healon5; Abbott
Medical Optics Inc., Santa Ana, CA) at the conclusion
of the procedure. The OVD maintains the anterior
chamber while the eye recovers from surgery and begins
to heal and while the glaucoma medications wear off. If
I augment trabeculectomy surgery with an
Ex-Press mini glaucoma shunt (Alcon
Laboratories, Inc., Fort Worth, TX), I still
use an OVD in the anterior chamber, but I
generally choose a viscoelastic that is not of
high viscosity in order to maintain the
anterior chamber and minimize the risk of
a pressure spike.
For shunt surgery, I favor the Baerveldt glaucoma implant (250 mm2; Abbott Medical Optics Inc.) and prefer not to ligate the tube. In order to prevent early overfiltration, I will place a high-molecularweight OVD (Healon GV; Abbott Medical Optics Inc.) in the anterior chamber at the end of the case and will also inject the OVD into the tube itself. Even when I use a valved shunt such as the Ahmed Glaucoma Valve (New World Medical, Inc., Rancho Cucamonga, CA), I will leave some viscoelastic in the anterior chamber.
I also find a high-molecular-weight OVD (Healon GV) to be of primary importance when I perform a canaloplasty combined with a deep sclerectomy.
The use of OVDs is pivotal to minimizing early postoperative complications and enhancing the long-term outcomes of glaucoma surgery.
F. JANE DURCAN, MD
OVDs are an essential tool in filtering surgery. I frequently
use an OVD to deepen the anterior chamber and protect the lens in a phakic eye. After making a
paracentesis, I inject the OVD into the anterior chamber.
I place enough to deepen the chamber and achieve
an adequate IOP to facilitate the incision and prevent
the forward movement of the iris and lens. In a pseudophakic
eye, this step often is not necessary. I usually
favor a cohesive viscoelastic such as Healon (Abbott
Medical Optics Inc.) for this maneuver for the ease of its
removal. I evacuate the OVD with irrigation through
the paracentesis prior to making the final adjustments
to the tension of the flap sutures. This timing allows the
fine-tuning of flow through the fistula to ensure adequate
drainage and maintain the anterior chamber
depth. In a very shallow eye, a dispersive agent such as
Viscoat (Alcon Laboratories, Inc.) may be needed to
maintain depth. In rare instances when I cannot maintain
its depth by adjusting tension on the suture, I will
leave the OVD in the anterior chamber.
In the case of a postoperatively flat anterior chamber, an OVD can be injected through the paracentesis at the slit lamp to deepen the chamber. I prefer to start with Healon, as it is the easiest to remove in the case of a pressure spike. If it proves inadequate to maintain the anterior chamber depth, I will inject Healon GV or Healon5. I am careful not to overinflate the eye and the bleb, because severe pressure spikes are a real risk with this maneuver.
I also use an OVD to protect the cornea against epithelial breakdown during filtering surgery if there is some already open on the field.
MOHAMMED ELMALLAH, MD
I do not routinely use OVDs in filtering
surgery. I have adjusted my technique to
minimize shallowing of the anterior chamber
intraoperatively. I incorporate an
Ex-Press shunt, typically the P-50 model,
into my filtering procedures. I preplace
two 10–0 nylon sutures in the scleral flap
prior to entering the anterior chamber. I
then make a temporal paracentesis with a
15° blade. I use a 25-gauge needle to enter
the anterior chamber. The needle is
occluded so that there is no fluid reflux
out of the anterior chamber until I remove
the needle from the eye. I then insert the
Ex-Press using the manufacturer's insertion
device. Immediately, I tie off both 10–0
nylon sutures holding the flap. Although
the anterior chamber will become shallow
during this process, it rarely becomes flat. I
then reform the anterior chamber with
balanced salt solution instilled through the
paracentesis and check aqueous flow at the flap, at
which time I will place more sutures if necessary. When I
first started using the Ex-Press, I would leave Healon in
the anterior chamber to avoid early postoperative
hypotony. I have found that this precaution is no longer
necessary.
I use OVDs in two specific situations when inserting tubes into the anterior chamber. During the tube's placement, if I find that it is getting caught in the iris, I will remove the tube and inject Healon through the sclerotomy to push iris tissue out of the way. Alternatively, I will inject Healon through the paracentesis and, either with my Healon cannula or a cyclodialysis spatula, will free up the distal end of the tube from the iris. The second situation in which I use an OVD is in the case of bleeding from the angle/iris root when I make the sclerotomy or insert the tube. Bleeding can occur in eyes with peripheral anterior synechiae or neovascular glaucoma. In these cases, I inject Healon through the paracentesis right next to the area of bleeding to provide a tamponade. I do not routinely leave an OVD in the anterior chamber at the end of the procedure.
SANDRA M. JOHNSON, MD
Viscoelastics can be a helpful adjunct to glaucoma filtering
surgery. I leave OVDs like Healon, Amvisc (Bausch +
Lomb, Rochester, NY), and ProVisc (Alcon Laboratories,
Inc.) in the anterior chamber of these eyes, especially if
the IOP was high (ie, over 30 mm Hg in general) preoperatively (Figure 2). This technique helps to maintain the
integrity of the globe during the first several days after
surgery. The goal is to lower the risk of hypotony and its
complications by allowing the IOP to decrease gradually.1
The OVD exits the tube or trabeculectomy slower than
aqueous. It takes about 2 days to clear. Viscoelastics are
also helpful in uveitic eyes, which often hyposecrete aqueous
during the early postoperative period. OVDs can be
reinjected into the anterior chamber as needed during
the postoperative period should the anterior chamber
become shallow and present the risk of lens-cornea touch.
Instilling an OVD can also temporarily elevate the IOP to
assist in the resolution of choroidal effusions. I often use
Viscoat in the clinic.
For all filtering surgeries, I check the digital pressure after injecting an OVD in the OR in order to leave the pressure in the range I want at the end of the case—a goal titrated to the status of the optic disc and taking into account the preoperative IOP. I would not want a high IOP in an eye with low-tension glaucoma or severe cupping, but an eye with an IOP that has been in the 30s or that has a sufficient nerve reserve can be left firmer.
During glaucoma implant surgery, I use an OVD to push back the iris if needed to facilitate a tube's insertion and to tamponade bleeding or even to move the blood to allow visualization. I only make an effort to remove the OVD if the IOP feels elevated when the cornea is compressed with a cannula. Generally, if the iris moves when I compress the cornea, I assume the IOP is in the normal range.
During combined surgery, after implanting the IOL, I make no effort to remove the OVD to lessen the hypotony while I complete the trabeculectomy and place sutures. In any trabeculectomy, I check the flow under the flap and the anterior chamber depth before I add more OVD at the end of surgery (Figure 3). I want the eye to maintain its own chamber without viscoelastic.
Some of the uses of OVDs discussed in this article are off label.
Louis B. Cantor, MD, is chair and professor of ophthalmology, the Jay C. and Lucile L. Kahn professor of glaucoma research and education, and director of the Glaucoma Service at the Indiana University School of Medicine in Indianapolis. He is a consultant to Abbott Medical Optics Inc. and has received research support from Alcon Laboratories, Inc. Dr. Cantor may be reached at (317) 278-2651; lcantor@iupui.edu.
F. Jane Durcan, MD, is in private practice at the Spokane Eye Clinic in Washington. She acknowledged no financial interest in the products or companies she mentioned. Dr. Durcan may be reached at (509) 456-0107; janedurcan@comcast.net.
Mohammed ElMallah, MD, is in private practice at Ocala Eye in Ocala, Florida. He acknowledged no financial interest in the products or companies he mentioned. Dr. ElMallah may be reached at (352) 622-5183; elmallah@post.harvard.edu.
Sandra M. Johnson, MD, is an associate professor of ophthalmology and a glaucoma specialist at the University of Virginia, Charlottesville. She acknowledged no financial interest in the products or companies she mentioned. Dr. Johnson may be reached at (434) 924-2808; smjeyes@gmail.com.
