Using Air to Remove Residual Viscoelastic

Recent literature has demonstrated that intraocular pressure (IOP) rise may be as much a function of impaired outflow facility as retained ophthalmic viscosurgical devices (OVD). If this is true, then the reputation of agents such as Vitrax (Allergan, Inc., Irvine, CA) and Viscoat (Alcon Laboratories, Fort Worth, TX) for causing IOP spikes was an undeserved result of surgeons' removal technique, or failure thereof. This discovery left me wondering: Can we remove OVDs more thoroughly, and if so, how can we tell that we have done so successfully?

CEASING THE INCIDENTAL HYPHEMA
Since training, I have directly irrigated the angle at the end of the case to improve displacement and removal of OVDs. On occasion, small vessels of the iris base would bleed, and I would place an air bubble in the anterior chamber to prevent a complete hyphema from forming. This bubble was nearly always a cause of delayed visual recovery, and each time I used it, I wondered whether the bubble or the hyphema would have been worse.

Bleeding from such small vessels should stop in about 1 minute, provided the flow is adequately impaired. I theorized the surface tension of a bubble would be sufficient for tamponade, provided its surface was directly against the source of bleeding. In early 2001, after identifying a site of bleeding following OVD removal, I completely filled the anterior chamber with air. After 60 seconds, I exchanged the air for BSS (Alcon Laboratories) via the irrigation-aspiration hand piece, and the bleeding had stopped. The next day, not only was there a complete absence of even circulating red cells, the IOP was normal. Unlike my previous experiences, this patient before me was a smiling 20/25 uncorrected. I have since used this technique perhaps 2 dozen times with nearly identical results.

VISCOELASTIC HIDING IN PLAIN SIGHT
After reviewing the videotapes of these hyphema cases, it struck me that small irregularities to the surfaces of the bubble could be seen in the chamber angle, usually far away from the site of bleeding. I realized that these irregularities were allowing a visualization of the retained OVD. The absence of an IOP spike in patients who had a hyphema while on the operating table was intriguing, and I hoped to find an association with the use of the bubble.

INITIAL ENDEAVORS
My first attempts at using the bubble to remove OVD were with the dual-use combination of Viscoat and ProVisc (Alcon Laboratories). My staff prepared a 3-mL luer lock syringe filled with air and attached to a 27-gauge cannula. Immediately after IOL placement, I placed the tip of the cannula between midiris and the angle just adjacent to the incision (Figure 1). I was trying to get as close to the subincisional space as possible. I injected air into the anterior chamber as I kept the posterior lip of the incision depressed. In the majority of attempts, the air would effectively exchange with the viscoelastic, displacing most of the Viscoat out of the incision. Similar success has been achieved with my current preferred regimen of Vitrax and BioLon (Akorn, Inc., Buffalo Grove, IL), but the cannula tip needed to be placed in the angle opposite the incision to have a similar displacement effect.

This air exchange tends to displace much of the OVD from the anterior chamber (Figure 2). Sometimes, this exchange will not displace much, but by observing the deformation of the surface of the bubble in the chamber, I can visualize where the bulk of the OVD is hiding in plain sight.

The irregularity to the surface of the air in the anterior chamber suggests that the majority of the viscoelastic remains in the angle, especially the subincisional space, relatively sheltered from contact with irrigation during cataract extraction. I now directly irrigate specifically to the sites of the retained material. I then use the irrigation-aspiration hand piece to flush the chamber until the visible viscoelastic disappears. Swirling OVD seems to disappear more quickly, and I suspect this was because less material is present to remove in general. (I use a “rock and roll” technique for removal behind the IOL.)

ENSURING VISCOELASTIC REMOVAL
The second bubble will now confirm the clearance of the OVD. This time, I am trying to exchange all of the residual solution in the anterior chamber with air, much as I had done with the hyphema (Figure 3). If the exchange is thorough, this bubble will conform directly to the angle, even slightly displacing the lens-iris diaphragm, and exposing any remaining OVD. I do not use this second bubble routinely, but I still employ it to ensure viscoelastic removal for patients with glaucoma or with previous pressure rise in the fellow eye. I also use this second bubble on patients who have difficulty sitting still at the slit lamp. After all, these can be the most challenging for tolerating the tapping of the side port on the first postoperative day.

I believe this technique has considerably decreased my need to intervene postoperatively to lower IOP. I am now convinced that spikes in IOP within the first 24 hours after cataract surgery are a result of three issues related to OVDs: the osmotic draw of the residual OVD, a specific patient's outflow facility, and residual OVD in the angle physically blocking normal outflow. With the assistance of these bubbles, I believe I have become more thorough at removing viscoelastics, and I no longer have to deal with the delays in recovery caused by minor hyphemas. As long as a measure of outflow facility evades us, I feel obligated to use some agent to lower IOP, be it topical Alphagan (Allergan, Inc.) or oral Diamox (Wyeth Pharmaceuticals, Radnor, PA), even when I can demonstrate thorough viscoelastic removal.

Steven H. Dewey, MD, practices in Colorado Springs with the Colorado Springs Health Partners. He has no financial interest in any of the products mentioned herein. Dr. Dewey may be reached at (719) 475-7700; deweys@prodigy.net