JAN 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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24 EW CATARACT January 2013 Device focus Not all blades serve all purposes by Michelle Dalton EyeWorld Contributing Writer When it comes to choosing instrumentation to make incisions, variables between disposable and reusable blades make a difference. D isposable or reusable? Diamond, sapphire, metal, or silicone? Depending on the type of surgery, the amount of surgical expertise, or the physical location of the operating room, different blades have different advantages. Generally speaking, diamond and sapphire blades are reusable and more expensive than their metal or silicone disposable counterparts. For some surgeons, the location of the surgery is the determining factor about which blade to use. "In my own practice, I used to use diamond blades. But at the surgery center, where there are multiple users of a single diamond blade, I started noticing a significant difference in sharpness from one day to the next," said Ayman Naseri, M.D., chief, Ophthalmology Surgical Service, San Francisco Veteran's Affairs Medical Center, and associate professor of clinical ophthalmology, University of California San Francisco. The inconsistent quality of the diamond tip "got frustrating," he said, as he was forced to change how he constructed a wound and the amount of pressure he would use in a split second. Although Uday Devgan, M.D., in private practice, Los Angeles, and chief of ophthalmology, Olive View – UCLA Medical Center, uses both a diamond blade and the newer femtosecond lasers in his practice, when he's teaching residents he prefers they use a steel blade, and cost is not the main reason. "With a steel blade, no matter how sharp it is, there's a tactile feedback that is beneficial to residents," he said. "No matter how sharp the blade is, the incision will be slower and have more resistance than with a diamond blade." Steel blades "require more effort to enter the eye," Dr. Devgan said. Deciding on blade type Diamond blades can be too sharp for a particular incision, said Steve A diamond keratome is used to make a corneal incision. Note the line across the tip of the blade that represents the piercing of Descemet's membrane. The incision is nearly square with dimensions that ensure optimal sealing, minimal induced astigmatism, and adequate access to the anterior segment during surgery. While this blade is made of a gem-quality diamond, its thinness causes it to be somewhat brittle, and care must be taken in handling it. With proper care, these blades can go 1,000 or more uses between maintenance. Safran, M.D., in private practice, Lawrenceville, N.J. He uses a diamond blade for the paracentesis, when he needs to use iris hooks, or when he makes a groove incision for scleral flaps. For his main incision, however (which ranges from 2.2-2.8 mm depending upon which machine he's using), he prefers metal blades. "I think it's easier to make a well-constructed incision with a metal blade because diamonds are actually too sharp," he said, and can cut the flap on the side. He prefers a technique of making a little groove, paralleling the cornea, and then bevelling down. At the surgery center, the staff are "much better at handling the diamond blades than they are at the hospital—in the hospital, often break and are more likely to be dropped," Dr. Safran said, adding those reasons to why he opts for disposable blades in hospital settings. The variability in diamond blade sharpness at the VA hospital was also a problem for Dr. Naseri in training residents. In Dr. Naseri's opinion, steel blades offer more consistency with their sharpness, and diamond blades can be inconsistent. The last diamond blade he used was trapezoidal, which presented issues with side-cutting elements in creating a multiplanar incision. "Uniplanar incisions that cut in the same plane don't pose a problem for blades with side-cutting features, but multiplanar incisions change the plane of the cut in the cornea," Dr. Naseri said, and this can lead to specific wound flaws. In resident cases, he has changed from a multiplanar incision created with a diamond blade to a single-plane incision created with a metal blade. Dr. Naseri found that the residents were forced to push too hard with a dull diamond blade, yet the same amount of force was problematic if they were using a sharp diamond blade. Dr. Naseri said the consistency of the metal blade sharpness has improved resident incision construction. Dr. Safran typically uses disposable blades for scleral flaps, but likes that a diamond blade can be used to more easily create a flap that starts at the limbus but moves away from him. Generally, however, Dr. Safran prefers metal blades for lamellar work. He feels it is easier to stay on plan with a metal blade that is beveled on one side. "If the blade is too sharp, it won't stay on the plane but will cut across it," Dr. Safran said. "It's like using a knife for the lasagna instead of a spatula." This phaco incision intentionally nicks the limbal vessels in order to provide better long-term healing. It was created with a femtosecond laser in an anatomic pattern that is difficult to replicate with a manual blade. Source (all): Uday Devgan, M.D. Pros and cons The positives to choosing a metal, disposable blade are cost and tactile feedback, according to Dr. Devgan. "They're not nearly as sharp as a diamond blade, and you don't get as clean an incision as with diamonds. For experienced surgeons, using a diamond blade is like a hot knife through butter—there's no tactile feedback," he said. Diamonds don't require routine resharpening, but they are expensive (running a few thousand dollars per blade) and are "as fragile as a potato chip because they're so incredibly thin," Dr. Devgan said. If surgeons want to change their preferred incision size from 2.8 mm to 2.2 mm, the diamond blade can be rehoned, but if the surgeon opts to go back to the larger size, a new blade is necessary, which adds to the cost as well. Sapphire blades fall somewhere between steel and diamonds, Dr. Devgan said. They're reusable and cost more than steel blades, and while they are less expensive than diamond blades, they may not last as long (somewhere in the tens or hundreds of uses). "Gem-quality diamond blades can be used ad infinitum unless they're damaged," Dr. Devgan said. The femtosecond lasers offer an additional type of incision and while they can create any architecture design that a surgeon can fathom, "the floor and the roof of the incision aren't quite as smooth as you get with a diamond blade," Dr. Devgan said. Number of users Newer surgeons should probably do their first couple hundred incisions with a metal blade before trying a diamond. "Part of any learning experience is to try all the different blades," Dr. Naseri said. "Each surgeon is going to make his or her own decisions based on what he or she likes. I provide my residents with a rationale about why I prefer metal blades, but in the end it's their decision." Dr. Naseri said if he's the only user at a surgery center, "I'd consider the diamond blade, but only ones without side-cutting elements. At an continued on page 26

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