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Inside Eyetube.net | Jun 2013

Benefits of a Disposable I/A Cannula

A smooth polymer tip may enhance the safety of this cataract surgery step.

Recent advances in cataract surgery, including improved phacoemulsification technologies and new ophthalmic viscosurgical devices (OVDs), have helped to reduce the incidence of intraoperative complications and made serious complications like dropped nucleus and corneal decompensation rare occurrences during phacoemulsification. Yet these developments do not always protect against capsular problems during irrigation and aspiration (I/A), and studies suggest that capsular rupture now occurs most frequently during this phase of cataract surgery. This may be because surgeons implanting premium IOLs are spending time polishing the capsule to remove residual cortex in an attempt to prevent posterior capsular opacification.

Capsule polishing is one way to help prevent posterior capsular opacification, but it can unfortunately induce anterior chamber instability. In our experience, biaxial I/A simplifies this surgical step by improving chamber stability and providing easier access to the entire circumference of the capsular bag during cortex removal. This article presents a new tool for biaxial I/A that may further enhance safety.

USE A DISPOSABLE DEVICE

Whenever possible, the use of disposable cannulas and tubing is preferable to avoid the threat of toxic anterior segment syndrome (TASS). Mamalis et al1 described the potential for residue and detergents to become trapped inside reusable hollow instruments, and the American Society of Cataract and Refractive Surgery (ASCRS) TASS Task Force has posted guidelines urging the use of disposable products.2 According to the guidelines, disposable cannulas and tubing should be discarded after each use because “these devices are sold without [disposable filter units] for cleaning, and thorough cleaning is difficult to achieve and to validate.” Specifically, reusable aspiration cannulas are difficult to clean properly due to the partially dead-end design of the lumen, with the aspiration port on the side of the shaft. Careful inspection of these cannulas under the microscope often reveals significant residual debris.

Unlike reusable versions, most disposable metal biaxial I/A handpieces do not have a smooth finished surface because the production process and the compromises associated with reducing cost result in unpredictable sharp aspiration port edges. After one of us (Dr. Tjia) experienced a few posterior capsule ruptures during polishing with these disposable devices, he abandoned their use.

A POLYMER TIP

Recently, Alcon introduced disposable bimanual I/A handpieces with polymer tips. The extremely smooth surface of the tips improves the safety of polishing the posterior capsule, and the large aspiration opening (0.3 mm) reduces the risk of capsular damage. During I/A, the surgeon can direct the distal opening of the polymer irrigation tip toward the capsular bag, avoiding the instability that results from direction of the fluid stream toward the ciliary sulcus.

The design of the disposable bimanual polymer I/A handpieces is modeled after 23-gauge metal reusable cannulas. The polymer aspiration tip, however, is significantly thicker than metal tips, resulting in increased outflow resistance. This necessitates more aggressive fluidics settings to provide the same aspiration characteristics. For instance, Dr. Tjia increased vacuum by approximately 20%, from 450 to 550 mm Hg, and increased aspiration flow by 10%, from 16 to 18 cc/min. When the correct machine settings are used, the polymer tip can be rubbed across the posterior capsule for polishing with an extremely low risk of capsular damage or posterior capsular tears. For video demonstrations of cataract surgery with polymer I/A tips, see eyetube.net/?v=lofor and eyetube.net/?v=nurew.

CONCLUSION

Disposable instruments are preferable to avoid the risk of TASS. However, many disposable I/A handpieces have rough edges that can cause posterior capsular tears or ruptures. By using bimanual instruments with smooth polymer tips, we have been able to reduce the incidence of these complications and maintain a safe environment for all surgical maneuvers.

Gabor B. Scharioth, MD, PhD, is in private practice at the Aurelios Augenzentrum in Recklinghausen, Germany. Dr. Scharioth states that he is a consultant to DORC International and Ivantis Inc. He may be reached at tel: +49 2361306970; e-mail: gabor.scharioth@augenzetrum.org.

Khiun F. Tjia, MD, is an Anterior Segment Specialist at the Isala Clinics, Zwolle, Netherlands. Dr. Tjia states that he is a consultant to Alcon. He is the Editor Emeritus of CRST Europe. He may be reached at e-mail: kftjia@planet.nl.

  1. Mamalis N, Edelhauser HF, Dawson DG, et al. Toxic anterior segment syndrome. J Cataract Refract Surg. 2006;32:324-333.
  2. ASCRS website. Task Force on Ophthalmic Sterilization. http://tassregistry.org/TASS_guidelines-CBC.pdf. Accessed May 7, 2013.

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