Capsule Rims: An Issue of Strength
A large plasma capsulotomy may be less likely to tear than a smaller capsulorhexis.
BY CHRISTOPHER KENT, SENIOR ASSOCIATE EDITOR

As you know, a big concern during capsulorhexis is avoiding creating a capsule tear. This issue has become a focus for Richard Fugo, M.D., creator of the Fugo Blade, a.k.a. plasma blade. (The blade is a lightweight, handheld, radio-frequency electrosurgical device that uses plasma technology to create incredibly sharp, resistance-free incisions. It operates on two c-cell flashlight batteries.)

Dr. Fugo explains: "A capsule tear is the result of the force exerted on the internal surface of the anterior capsule rim. According to physics, force equals pressure times the area subjected to the pressure. So, one way to decrease the likelihood of a capsule tear is to enlarge the capsulotomy, which decreases the area being subjected to the force. We compared 5-mm capsulotomies with 7-mm capsulotomies, and the larger ones were significantly less likely to tear.

A study of 75 porcine eyes conducted at the Storm Eye Institute in Charleston, SC, compared the amount of stretching required to cause a capsule tear following different capsulotomies. The Fugo blade rim has tested even stronger in pediatric surgery, as well as in adults when the capsulotomy is enlarged.

"Also, force applied in one consistent direction, or vector, is cumulative; force applied at a number of different vectors isn't. As Dr. David Apple demonstrated, the edge pro- duced by the plasma blade has a wavy, 'postage stamp' shape. The straight, smooth edge of a standard capsulorhexis amplifies force vectors, increasing the likelihood of tearing into the posterior capsule. The plasma blade edge puts force vectors out of synch, so they don't produce large tears. Tears that do occur don't continue into the posterior capsule."

Influential Factors

Rim strength has been under study by M. Edward Wilson, M.D., at the Storm Eye Institute, part of the Medical University of South Carolina in Charleston. "The Fugo blade capsulotomy is nearly as strong as a manual tear capsulorhexis," says Dr. Wilson. (See graph, above, right.) Scanning electron microscopy has also revealed that, unlike diathermy, the plasma blade causes no burn or blistering at the margin rims.

Studies of pediatric patients have been even more favorable to the plasma blade. The rim created by the plasma blade in pediatric surgery was considerably stronger than that created using standard capsulorhexis, and -- according to Dr. Wilson -- easier to create for the surgeon. "The Fugo blade is an impressive instrument," he says.

Increasing the Width to 7 mm

Dr. Fugo notes that the slight disadvantage in rim strength (compared with standard capsulorhexis) only applies if rim size is identical. "You can compensate for this by increasing the width to 7 mm -- something easily done with the plasma blade. This actually makes the plasma blade rim stronger than the standard capsulorhexis rim."

For more information about the plasma blade, contact William Knepshield, president of Medisurg Research and Management Corporation, at (610) 277-3937, or visit www.fugoblade.com on the Internet.