In search of the ideal viscosurgical device

Whether they use one agent or a combination, surgeons agree that OVDs are crucial.

With the ophthalmic industry bracing to meet the surgical needs of a generation of baby boomers now entering their cataract-prone years, the importance of ophthalmic viscosurgical devices may be greater than ever.

Although they are integral to many cataract surgery techniques, ophthalmic viscosurgical devices (OVDs) — commonly known as viscoelastics — are often overshadowed by the hype surrounding new implant and phaco technologies.

Yet surgeons are becoming increasingly aware of the need for new materials and techniques that make cataract surgery safer and more efficient. Companies have obliged by developing more versatile viscoelastic products and packages that combine dispersive and cohesive qualities.

For this article, Ocular Surgery News spoke to surgeons who use the leading OVDs in their practices daily. Their remarks provide a cross-section of opinions on these important but often-overlooked surgical adjuncts.

Can one product do all?

“Everyone is searching for the one ideal agent,” said Satish Modi, MD, in private practice in New York.

“The ideal product would allow us to do a capsulorrhexis with a perfect tamponade, to do phaco with immense protection of the endothelium and posterior capsule, to fill the capsular bag, put the implant in safely and remove every vestige of the viscoelastic product out of the eye,” Dr. Modi told Ocular Surgery News.

Dr. Modi is among those who believe that no single OVD offers all the characteristics necessary to prevent the trauma caused by cataract surgery. Therefore, he uses a dual system, Alcon’s DuoVisc, which couples the dispersive Viscoat (3% sodium hyaluronate, 4% chondroitin sulfate) with the cohesive ProVisc (1% sodium hyaluronate).

Dr. Modi presented the results of a 1-year study comparing the DuoVisc system with three other products at a session on OVDs during the annual meeting of the American Society for Cataract and Refractive Surgery.

He found that, in 125 patients, the DuoVisc system provided a better clinical outcome than did a regimen relying on just one viscoelastic, whether it was cohesive, dispersive or adaptive.

Outcome measurements included pachymetry, cell counts, IOP, vision and presence of striae, Dr. Modi said.

In all four categories, he concluded that DuoVisc outperformed the other products, which included Amvisc Plus (sodium hyaluronate, Bausch & Lomb), Healon GV and Healon5 (both sodium hyaluronate, Pharmacia).

“Using high-flow phaco, we had increased endothelial cell loss, increased pachymetry, corneal striae and decreased best corrected visual acuity with Healon5, Amvisc plus and Healon as opposed to with Viscoat,” Dr. Moti said.

Dr. Moti said he believes DuoVisc combines the best that cohesive and dispersive agents have to offer. He said his experience with Healon5, which was highly praised by other presenters at ASCRS as the ideal OVD for its adaptive properties, did not convince him that any one viscoelastic device can do the job.

“With DuoVisc, depending on your needs you can use one agent or the other,” he said. “Admittedly, since Healon5 is a super-cohesive, if you have a fair amount of positive pressure and wanted to tamponade the area well, you could use it. But the minute you try to stick an instrument into the eye, the Healon5 is gone. You have to put more Healon5 in the eye before you start phaco or else it all comes out of the eye and leaves the cornea unprotected,” Dr. Moti said.

New product, new techniques

Supporters of Healon5 at the same ASCRS session disagreed with Dr. Moti, contending that this relatively new material, known as a viscoadaptive or fractionable OVD — used with specific new techniques — makes cataract surgery safer by improving control over the intraocular environment during surgery.

Healon5 combines the qualities of pseudo-dispersive and cohesive behaviors, according to several speakers at the ASCRS session. The material has exceedingly high viscosity at low shear rates, and molecules actually fracture when subjected to sudden high shear rates, instead of beginning to flow.

Steve A. Arshinoff, MD, FRCSC, who moderated the ASCRS session on OVDs, said Healon5 represents the best single option on the market for surgeons because of its proven success in maintaining stability within the anterior chamber and its ease of use. He and other users of Healon5 said it can behave like a dispersive agent when filling the capsular bag for IOL injection, or it can act as a cohesive to maintain space between tissues to allow insertion of the phaco tip.

Dr. Arshinoff conceded that the learning curve for Healon5 can be steep and that its use requires some modifications of surgical technique.

“Healon5 came along and combines the best of all (existing options). It may require education and new learning technology,” Dr. Arshinoff said.

To take advantage of the unique characteristics of Healon5, Dr. Arshinoff developed the ultimate soft shell technique (USST). In USST, Healon5 is used in combination with balanced salt solution to facilitate capsulorrhexis and other maneuvers.

The USST technique uses the high viscosity of Healon5 to stabilize the anterior chamber, while the very low viscosity of balanced salt solution (the lowest-viscosity surgical fluid) allows easy maneuverability of surgical instruments.

For capsulorrhexis, Dr. Arshinoff proposes that surgeons fill the anterior chamber to 75% with Healon5 and then inject balanced salt solution under that layer. Healon5 prevents the solution from leaking through the incision. He said highly satisfying results can be obtained by varying the amount of balanced salt solution and the fluid aspiration rate setting during capsulorrhexis, hydrodissection and lens implantation.

Another presenter at ASCRS, Richard Hoffman, MD, described his experience using Healon5 to stabilize the anterior chamber following trabeculectomy. He performed a study to examine the potential for pressure spikes, flattening of the anterior chamber and damage to the corneal endothelium using the viscoadaptive agent after glaucoma surgery.

He conducted a small prospective study on eight eyes undergoing trabeculectomy. He and his colleagues found that none of the eyes developed a flattening of the anterior chamber or pressure spikes, and that corneal endothelial cells appeared to tolerate prolonged Healon5 exposure in the anterior chamber following trabeculectomy.

“I am now using Healon5 routinely for this indication,” Dr. Hoffman said.

Striking the balance

For standard cataract procedures, Bausch & Lomb’s Amvisc Plus is another frontrunner among the viscoelastic products. Users said this product attempts to meld the best characteristics of dispersive and cohesive products.

With a molecular weight of approximately 1.5 M daltons, Amvisc Plus is considered moderately cohesive, meaning it will remain in the eye during the procedure but is not difficult to remove from the anterior chamber.

Andrew Tharp, MD, of the Wellborn Clinic in Illinois, said he is concerned not only with how easily a viscoelastic is removed, but also with what the product does while in the eye. He said he has found Amvisc Plus to provide a good balance between cohesive and dispersive properties.

Amvisc plus has a smaller molecular size than other more cohesive products such as Healon, he said, and this feature agrees with surgeons who prefer to work with more highly concentrated viscoelastic products.

“I like the idea of not having to go in the eye too many times. With the smaller molecule size, Amvisc Plus will stay in the eye during phacoemulsification, and that is very important to me,” Dr. Tharp said. He said it works from start to finish and generally does not have to be replenished once in the eye.

Dr. Tharp noted that he finds problems with IOP spikes infrequent but not unheard of with Amvisc Plus.

He also pointed out that Amvisc Plus has a relatively high pseudoplasticity index, meaning its viscosity drops rapidly as the shear rate increases. While in the eye, Amvisc Plus also enables him to maintain a clear view of what he is doing without having to worry about bubbles.

“Amvisc Plus is my workhorse product for basic cataract procedures,” Dr. Tharp said.

Another viscoelastic agent available from Bausch & Lomb is Ocucoat (2% hydroxypropyl methylcellulose). Ocucoat is a cohesive OVD with low molecular weight, making it relatively easy to remove from the anterior chamber.

Clarity is key

Clarity is an issue that can set an OVD apart from the rest, some practitioners said.

For example, Vitrax (sodium hyaluronate, Advanced Medical Optics) a dispersive agent, is an ideal product to use when teaching residents how to perform cataract surgery because it provides excellent clarity, according to Robert Noecker, MD, who practices in Tucson, Ariz.

“Vitrax behaves a lot like Viscoat, in that it really stays in the eye and does a great job of protecting the cornea,” Dr. Noecker said. “The key difference is that because Vitrax has less chondroitin sulfate than Viscoat, it helps clarity and avoids haze.”

When it comes to teaching residents, Vitrax can also be helpful because it does not come out of the eye too easily, he said.

“To teach residents, it is important to have something very stable (in the eye). This makes it much easier for me to teach them to do a capsulorrhexis, for example,” he said.

With glaucoma patients, too, Vitrax works well because it is not difficult to remove from the eye. This cuts down on the risk glaucoma patients face of pressure spikes, Dr. Noecker said.

Vitrax also works well as a tool for tissue manipulation in glaucoma patients with small pupils.

“I have to do a lot of pupil manipulation as a glaucoma surgeon, and I find that Vitrax is really good at stretching the pupil,” Dr. Noecker said.

CoEase (1.2% sodium hyaluronate), also from AMO, is a cohesive OVD with a light molecular weight that feels closer to an adhesive, according to the company.

Dr. Noecker said he also uses CoEase as his “multi-purpose” agent, both at the beginning of the case to perform the capsulorrhexis and at the end of the case to implant the IOL.

“When you want to use just one tube of viscoelastic solution, this has a nice staying power in the eye. It is versatile enough for the whole case,” he said.

Dr. Noecker said he relies upon CoEase in 90% to 95% of his cases. Sometimes he uses it in conjunction with Vitrax in patients in which he is more worried about the endothelium or in cases that require more stability in the anterior chamber.

“You can do a double layering so that Vitrax fills the anterior chamber up against the cornea and then you add a secondary layer of CoEase underneath during the capsulorrhexis,” he said. “You can maintain the chamber with Vitrax and support it with CoEase.”

Comparing similar products

One surgeon said he has enjoyed good results using a hydroxypropyl methylcellulose viscoelastic for years, but he recently began to introduce STAARVisc II (sodium hyaluronate, STAAR Surgical) into his surgical technique.

“I’m still using Ocucoat, but now I’m comparing it to STAARVisc II. I am interested in studying the differences in pressures produced by the two products on the first postop day,” David Brown, MD, of Ft. Myers, Fla., told Ocular Surgery News.

Dr. Brown said he has so far been impressed with how STAARVisc II handles in the eye, especially in terms of its stability and the ease with which it is removed at the end of the case.

He said he feels STAARVisc II is thicker than Ocucoat and behaves similarly to Healon5. Dr. Brown said he does not need to use STAARVisc II in combination with another OVD because of its versatile nature.

“Right now I think the most impressive part of my early experience with the STAARVisc II is that it does maintain such a good, stable anterior segment. And on removal, it also seems to follow well, so I don’t get the postop pressure spikes,” Dr. Brown said.

Dr. Brown called the viscosity of STAARVisc II “almost ideal.”

“It’s thick enough to do the job but not so thick as to impede surgical manipulation, dissections and so forth,” he said.

Room for agreement

Despite the variety of opinions, surgeons tend to agree on the basic qualities they all look for in an OVD. The criteria, it seems, are actually quite simple.

“All surgeons are looking for something that maintains the chamber and stays in the eye at the beginning of the case. But at the end you want to be able to get it out quickly because you don’t want to have pressure spikes,” Dr. Noecker said.

Dr. Brown agreed, saying that if he could have wish granted when it comes to viscoelastics, it would be “something to prevent pressure spikes.”

“At this point, most of us accept that as one of the things you have to do your best to prevent. Maybe our surgical technique is also a factor there,” Dr. Brown said.

Price is another critical aspect that will determine which products succeed, as Dr. Modi pointed out.

“One more attribute that the ideal agent should have it that is should be cheap, but that isn’t going to happen — at least not any time soon,” he said.

Yet Dr. Modi, who is originally from India, said he often tells surgeons from developing nations that investing in pricier products could ultimately save them time and money.

“I tell them: If you wind up with a patient who has corneal edema and not seeing well, you’re going to be seeing the patient more often and then you’re going to get negative referrals. It’s worth every penny,” Dr. Modi said.

For Your Information:

• Satish Modi, MD, can be reached at 23 Davis Ave., Poughkeepsie, NJ 12603; (914) 454- 1025; fax: (854) 454- 5881.
• Steve Arshinoff, MD, can be reached at 2115 Finch Ave. West, Suite 316, Toronto, ONT M3N 2VG, Canada; (416) 745-6969; fax: (416) 745-6724.
• Richard S. Hoffman, MD, can be reached at Drs. Fine, Hoffman, & Packer, 1550 Oak St., Suite 5, Eugene, OR 97401; (541) 687-2110; fax: (541) 484-3883.
• Andrew W. Tharp, MD, can be reached at the Welborn Clinic, 4411 Washington St., Evansville, IN 47714; (812) 474-7138; fax: (812) 473-8875.
• Robert J. Noecker, MD, can be reached at 655 N. Alvernon Way Ste 108, Tucson, AZ 85711; (520) 321-3677; fax: (520) 321- 3991.
• David C. Brown, MD, can be reached at Eye Centers of Florida, 4101 Evans Ave. Fort Myers, FL 33901; (239) 939-3456; fax: (239) 936-8776.

• Alcon, the maker of Viscoat, ProVisc and DuoVisc, can be reached at 6201 South Freeway, Fort Worth, TX 76134; (817) 293-0450; fax: (817) 568-6142.
• Pharmacia, the maker of Healon and Healon5, can be reached at 100 Route 206 North, Peapack, NJ 07977; (908) 901-8592.
• Advanced Medical Optics, the maker of Vitrax and CoEase, can be reached at 1700 E. St. Andrews Place, Santa Ana, CA 92799; (800) 449-3060; fax: (866) 872-5635.
• Bausch & Lomb, the maker of Amvisc Plus and Ocucoat, can be reached at 1400 N. Goodman St., Rochester, NY 14609; (585) 338-6536; fax: (585) 338-0898.
• STAAR Surgical, the maker of STAARVisc II, can be reached at 1911 Walker Ave., Monrovia, CA 91016; (626) 303-7902; fax: (626) 303-2962.