EyeWorld India March 2013 Issue

53 EW NEWS & OPINION March 2013 Rigging the game to win in challenging cataract cases P ractitioners can only play the cards that they are dealt in challenging cataract cases. But that doesn’t mean that they can’t stack the deck in their favor. Here’s how the latest cohesive, dispersive, and viscoadaptive OVDs can help do just that. Bonnie An Henderson, MD , assistant clinical professor, Harvard Medical School, Boston, Mass., USA, believes in planning ahead particularly in a challenging cataract case. “I prepare for challenging cases by thinking through each step and what type of viscoelastic may be the best choice for that action,” Dr. Henderson said. Playing a cohesive hand She finds that cohesive OVDs have unique characteristics that can be very useful in challenging cases. “Benefits of cohesive OVDs include the ability to maintain space, clearer visualization, and the ability to remove the OVD quickly and easily,” Dr. Henderson said. One of the strengths of these cohesive OVDs is their ability to create space. “Cohesive OVDs, especially higher molecular weight OVDs, can be used as a physical barrier to keep ocular tissues compartmentalized,” Dr. Henderson said. “For example, when attempting to manipulate the iris during IFIS (intraoperative floppy iris syndrome) cases or when suturing a PCIOL to the iris, a high viscosity cohesive can help compress and isolate the iris tissue.” Also, she emphasized, if there is positive pressure with chamber shallowing, a high viscosity OVD will help maintain a formed chamber and flatten the anterior surface of the lens, and this can help when attempting to complete a capsulotomy. For routine cases and for filling the bag, Dr. Henderson’s go-to OVDs include ProVisc (Alcon, Fort Worth, Texas, USA/Hünenberg, Switzerland), AmVisc (Bausch + Lomb, Rochester, NY, USA), or Healon (Abbott Medical Optics, AMO, Santa Ana, Calif., USA). In instances requiring enhanced stability of the anterior chamber, however, she will use AmVisc Plus (Bausch + Lomb) or Healon GV (AMO). Dealing out dispersives Likewise, dispersive OVDs can play an important role in challenging cases. “Since they adhere to surfaces like the corneal endothelium, these agents protect against ultrasonic or mechanical injury,” Dr. Henderson said. She also finds that because challenging cases tend to take longer, dispersive viscoelastics can decrease the amount of corneal damage, as well as resulting corneal edema. Another key characteristic of dispersive OVDs in challenging cases is their ability to remain in place. “They do not exit the eye easily,” Dr. Henderson said. “This ensures that the anterior chamber does not collapse prematurely during an inopportune moment.” Roger F. Steinert, MD , chair, Department of Ophthalmology, University of California, Irvine, Calif., USA, and director, Gavin Herbert Eye Institute, sees dispersives as valuable in situations where practitioners are concerned that they’re not going to be able to ultimately remove all of the OVD—something that could cause pressure elevation. “The larger the molecular weight on average, the more likely you are to get higher pressure,” Dr. Steinert said. This makes a lighter dispersive OVD an asset in an open capsule case, where some viscoelastic will be left behind. Also in cases involving very dense nucleus, where there is often not much of a protective epinucleus, he finds that dispersive OVDs have a role. During the second half of phacoemulsification, the posterior capsule starts to get exposed and either the phaco tip itself or a sharp piece of nucleus can cause a rupture, he warned. To protect against this, Dr. Steinert uses a technique that he dubs the “visco vault.” “As soon as I can see some red reflex and I’ve got enough of the nucleus out that I can get pretty deep behind the nucleus, I create an artificial epinucleus with a dispersive OVD,” Dr. Steinert said. “It can do a remarkable job in keeping the posterior capsule back and keeping it safe.” Steve A. Arshinoff, MD , clinical instructor of ophthalmology, University of Toronto, explains that by their very nature, dispersive OVDs, which demarcate spaces, are used in more complicated cases. “A space becomes a complicated case when you wish to partition the space,” he said. He pointed to protecting the endothelium in Fuchs’ dystrophy cases. “What you’re saying is, you want to partition the space, the adjacent endothelium, so that there’s no fluid flow there,” Dr. Arshinoff said. Likewise, in a tamsulosin hydrochloride case, Experts provide OVD cheat sheet by Maxine Lipner Senior EyeWorld Contributing Writer he stressed, you want to partition the iris in a way that it doesn’t get exposed to the fluid turbulence and flop all over the place. In both cases, a dispersive OVD will remain in place and provide the needed buffer. To maximize effectiveness, he often pairs the unique properties of a dispersive agent with those of a cohesive. He uses the cohesive agent to induce pressure and the dispersive to partition space. For example, for a case involving a traumatic cataract with two or three clock hours of broken zonules, Dr. Arshinoff advised painting the area with a dispersive viscoelastic and then putting a viscous cohesive in the eye to slowly apply pressure. “Then you do the capsulorhexis and start your surgery,” he said. “But before you try and induce any flow in the eye, you hydrodissect gently and try to put in a capsular tension ring in the bag.” This broadens the shape of the lens so this covers the disinsertion of zonules. The only thing in front of the ring is the dispersive viscoelastic. “The case then becomes a regular case,” he said. For his “go-to” dispersive agent, Dr. Arshinoff prefers the original Viscoat (Alcon) to the others, which he terms copies. “If it were my mother [as the patient], I would choose Viscoat just because we have a longer track record,” he said. Dr. Henderson likewise favors Viscoat. Dr. Steinert has switched to using the dispersive Healon EndoCoat (AMO). “What surgeons are observing is that EndoCoat, because it is purely hyaluronic acid, does not have the problem with viability that some people continued on page 54