Healon5 completes IOP trial

New viscoadaptive material is cohesive at low flow rates, dispersive at high flow rates.

BOSTON — Surgeons are treating the latest high-viscosity viscoelastics as a new type of instrument to apply in their phaco procedures.

One new viscoelastic material, Healon5 (sodium hyaluronate 2.3%; Pharmacia Corporation, Peapack, N.J.), works as a viscoadaptive, meaning it adapts to the surgical environment. At low shear rates it has the properties of a cohesive, but at high shear rates it acts like a dispersive.

Because Healon5 can be fractured, it behaves as a dispersive at very high flow rates. Manfred R. Tetz, MD, compared Healon5 with a ball of wool. When pulled on slowly, the entire amount can be moved. By pulling fast, pieces can be ripped off.

This dual nature will improve the use of viscoelastics, according to speakers at the American Society of Cataract and Refractive Surgery (ASCRS) meeting.

Modern surgery

According to Kerry D. Solomon, MD, Healon5 “is the first of a new line of viscoadaptives that’s really been developed to meet some of the challenges of modern surgery.”

Dr. Solomon tested a small number of eyes for Food and Drug Administration (FDA) trials. Most surgeons are adopting high-flow, high-vacuum and low-ultrasound procedures. Dr. Solomon explained that during high flow rate phaco procedures, cohesive viscoelastics tend to exit the eye.

Because surgeons are using low ultrasound and high vacuum to remove the lens material, turbulence and flow are the main threats to the endothelium. Having a viscoelastic or a viscoadaptive that stays in the eye is going to become more important, Dr. Solomon said.

“When we’re using vacuums of 300 mm Hg to 500 mm Hg, we’re using flow rates of 30 cc/min to as high as 60 cc/min,” he said. “This is where this product is going to shine and do its best.”

Robert J. Cionni, MD, tested approximately 80 eyes in the FDA study. His surgical maneuvers begin by injecting Healon5 180° across from the incision until the chamber is full. At this point, he sees the iris lens diaphragm flatten and feels a slight increase in resistance to the plunger.

“Once you’ve seen that occur, do not continue to inject and do not overfill, because this is a very cohesive viscoelastic and you can raise the pressure in the eye dramatically. That would be especially cautioned in patients with weak zonules,” Dr. Cionni said.

During hydrodissection, he also recommended leaving an escape route of balanced salt solution by injecting it as the cannula enters the chamber. This leaves a track for the balanced salt solution to escape the chamber if hydrodissection is too aggressive.

“If you’re going to hydrodissect through the sideport incision, don’t be overly aggressive because the Healon5 will not evacuate the chamber and you can markedly raise the pressure again,” Dr. Cionni said.

Check the pressure

Steve A. Arshinoff, MD, FRCSC, a paid consultant for Pharmacia Corporation, chaired the viscoelastics session at ASCRS and participated in the FDA trials for the product. The intraocular pressure (IOP) trials ended May 5.

Dr. Arshinoff did a study looking at the postoperative IOP after using Healon, Healon GV and Healon5 in bilateral paired eye cataract surgery.

A small study of 38 patients underwent bilateral cataract surgery. One eye received Healon and the other one Healon GV. In a second group, one eye received Healon GV and the other received Healon5.

Postoperative IOP rose significantly in all eyes at 5 hours postoperatively, had returned to normal at 24 hours postoperatively and then fell to slightly below normal at 7 days, Dr. Arshinoff said. There was no difference in the postoperative pressures in any of these groups at any point.

He examined the patients who had pressure spikes. Patients showed a similar IOP spike at 5 and 24 hours, and there were no significant differences in the severity of IOP spikes among Healon, Healon GV and Healon5.

The 10 patients who experienced an IOP spike in one eye usually experienced a similar spike in the other eye using a different viscoelastic. This happened with concordance of 85%, Dr. Arshinoff said.

If the pressure was more than 21 mm Hg in one eye at 5 and 24 hours postop, it was more than 21 mm Hg in the fellow eye 75% of the time. If the pressure was less than 21 mm Hg postoperatively in the first eye, it was less than 21 mm Hg in 88.7% of these patients.

In one patient, IOP was 39 mm Hg in one eye at 5 hours postoperatively. The fellow eye had a different viscoelastic and had an IOP of 38 mm Hg. In another patient, one eye had at 5 hours postoperatively an IOP of 29 mm Hg in one eye and 22 mm Hg in the fellow eye, again with different viscoelastics.

Only one patient had a pressure spike in one eye only, and three patients with postoperative pressure spikes were found to have undiagnosed glaucoma upon further investigation, Dr. Arshinoff said.

IOP spikes may be more a patient response to surgery than a function of the individual viscoelastic, Dr. Arshinoff said. Pressure spikes have been reported to occur at a similar rate in eyes that use balanced salt solution alone.

“A severe IOP spike may be indicative that we should investigate the patient for glaucoma because one-third of these patients actually had glaucoma,” Dr. Arshinoff said.

So, he examined the results from the phase 3 Healon5 IOP study of 359 nine eyes — 187 with Healon5 and 172 with Healon. The complications of surgery included two posterior capsule ruptures with Healon5 and one with Healon. There was no significant difference in the postoperative IOP spikes reaching higher than 30 mm Hg in patients operated with Healon5 (11%) compared with Healon (10%).

Capsulorrhexis

Clinical trials allowed surgeons to test the viscoelastic’s handling characteristics, as well as test for safety and efficacy. Surgeons have already found surgical pearls they can use during phaco.

The psuedoplasticity of Healon5 makes it much easier to handle, Dr. Solomon said. There is very little chamber shallowing and fluid escape, so a small amount of Healon5 maintains a very stable chamber, Dr. Solomon said.

“With this product, unlike any other product I’ve used, I’ve found I really don’t need to be concerned about my rhexis extending out,” he said. “I’ve found that I have really more control than any other products that I’ve used. In fact, if I wasn’t careful, I tended to make my rhexis a little smaller and I really had to remind myself to continue to bring that tear around and stay external.”

According to Dr. Cionni, “Capsulorrhexis is a different bird altogether when using Healon5. Those of you who are used to Healon GV may feel more comfortable and it may feel more familiar to you. Being a Healon user, I find that Healon5 has different space-occupying properties.”

He creates a more peripheral capsulotomy, unlike Healon, which required that he prevent the capsular tear from going peripherally.

Removing Healon5

Surgeons who use Healon5 have found success with a second removal method to clear it from the eye. While most viscoelastics can be cleared with the rock and roll method, some surgeons using Healon5 applied a two-chamber technique.

The two-chamber technique, suggested by Dr. Tetz and Eugenio Leite, MD, allows surgeons to clear the viscoelastic from the bag and then from the anterior chamber. The viscoelastic does not evacuate from the anterior chamber during this surgical maneuver and the eye remains stable throughout.

“While this may seem a very tenuous thing for us to do at least in the United States, I’ve found it to be much more efficient and much more controlled,” Dr. Solomon said.

According to Dr. Cionni, the lens will remain decentered after placement in the bag. He leaves the lens decentered, because it leaves open access to the posterior capsular bag to remove viscoelastic from behind the IOL.

“After aspirating the Healon5 from behind the IOL, I move anterior to the IOL and use a rock and roll maneuver,” he said. “The vacuum setting is at 250 mm Hg. I use a 0.5-mm aspiration port with a metal tip. That’s my standard viscoelastic removal tip. It’s not specially designed for Healon5. The flow rate is at 34 cc/min and the bottle height is at 50 cm.”

This two-chamber approach is different from the rock and roll method used with previous viscoelastics, Dr. Tetz said. Emptying the bag and then the anterior chamber is faster and possibly safer, he said.

He places the irrigation and aspiration tip under the lens in one move without irrigation engaged. Healon5 empties out of the bag quickly, and also will empty quickly from the anterior chamber.

“While we are doing so, the iris remains stable, we don’t get a flat anterior chamber, and this is very safe because the infusion flow keeps the posterior capsule at a distance while you’re working in the compartment of the bag,” he said.

He has reduced his removal time markedly, to less than 20 seconds.

He measured the removal time of Healon5 in 30 eyes following a standardized phaco with a foldable IOL implantation. The removal time was 43.7 seconds for the rock and roll and 18.4 seconds for the two-chamber approach.

“I start to think about [Healon5] as a new instrument that someone gave to me, and that with this new instrument, we can improve quite a bit,” Dr. Tetz said.

During capsulorrhexis, Healon5 behaves more like Healon GV. Its “space-occupying” properties distribute forces differently.	During IOL insertion, when dialing the IOL leave it displaced for Healon5 removal.	Healon5 remains anterior to the IOL prior to removal. Then using a “rock and roll” method, the viscoelastic is cleared. Vacuum setting is 250 mm Hg; flow rate is 34 cc/min and bottle height is 50 cm.

The adaptive behavior of Healon 5 is its ability to become fracturable as fluid flow rate and therefore anterior chamber turbulence is increased. It is a super-cohesive at low flow rates. This is compared with Viscoat and Healon GV, which demonstrate consistent dispersive and cohesive rheologic behavior, respectively, across the entire range of surgical flow rates.

For Your Information:

• Steve A. Arshinoff, MD, FRCSC, can be reached at 2115 Finch Ave. W, Toronto, Ontario M3N 2V6 Canada; (416) 745-6969; fax: (416) 745-6724. Dr. Arshinoff has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for Pharmacia Corporation.
• Kerry D. Solomon, MD, can be reached at the Medical University of South Carolina, 171 Ashley Ave., Charleston, SC 29425; (843) 792-8854; fax: (843) 792-4854. Dr. Solomon has no direct financial interest in any of the products mentioned in this article. He is a paid consultant for Pharmacia Corporation.
• Robert J. Cionni, MD, can be reached at the Cincinnati Eye Institute, 10494 Montgomery Road, Cincinnati, OH 45242; (513) 984-5133; fax: (513) 984-4240. Dr. Cionni is a paid investigator for the Healon5 study. He is not a paid consultant for any companies mentioned in this article.
• Manfred R. Tetz, MD, did not participate in the preparation of this article.

• Pharmacia Corporation can be reached at 100 Route 206 N, Peapack, NJ 07977; (908) 901-8000; fax: (908) 901-1874.