Advantages of Sleeveless Bimanual Microincision Cataract Surgery

Over the past several years, there have been significant improvements in phacoemulsification technology. New-generation phaco software with micropulse delivery of ultrasonic energy allows for cataract removal without significant heat generation at the phaco tip. This has led some surgeons in the United States, and many more internationally, to start performing bimanual cataract surgery without an irrigating sleeve around the phaco needle.

This technique of bimanual microincisional cataract surgery (MICS) can now be used confidently with very low risk of thermal damage to the eye. After almost 5 years of experience with the bimanual microincisional technique, many surgeons have found that it has advantages over traditional sleeved coaxial phacoemulsification. Some feel that eventually it may become the preferred technique, once implants that can be injected through a 1.5 mm wound are readily available. Currently, these implants are available only outside of the United States, but they may become available here sometime in 2008.

One feature appreciated by surgeons is the smaller wound size that is created with MICS. Most surgeons prefer using 19- or 20-gauge instruments, which produce wounds that are 1.2 mm to 1.6 mm in size. These smaller wounds tend to provide a very stable and deep chamber throughout the procedure, with very little risk of chamber shallowing or collapse. These "micro wounds" are especially helpful in challenging cases such as floppy iris syndrome, where the iris tends to prolapse out of the wound.

With MICS, there is also minimal shallowing of the chamber when the instruments are removed from the eye. Some surgeons who use microincisional implants have found that these smaller wounds induce less astigmatism than does the larger coaxial wound. In theory, there also may be less risk of wound leakage and a lower incidence of endophthalmitis with smaller-incision cataract surgery.

MICS surgeons have also come to enjoy the improved and controlled fluid dynamics that result from divorcing irrigation from aspiration and ultrasound. Most would agree that the bare phaco needle is more efficient at cutting through nuclear material without a sleeve. A sleeve often restricts sculpting, and the irrigation around the phaco needle can push nuclear material away from the phaco tip, preventing a good purchase. These 2 difficulties are not encountered when using the separate irrigation unsleeved phaco technique. Additionally, there is very predictable and controlled movement of the fluid in the eye when the irrigation handpiece is held still and pointed in 1 direction away from the phaco tip, while the phaco handpiece is gently manipulated in the center of the eye in order to grab nuclear particles. This process circulates the fluid and cataract material in an organized pattern, and it naturally flows toward the phaco aspiration instrument. Alternatively, when fluid is entering the eye through an open-ended irrigator, the stream of fluid can be used to push, dislodge, manipulate, or move nuclear particles around inside the eye. This "fire hose" technique is very helpful in small-pupil cases because it allows the phaco needle to remain still and centered in the eye while the open-ended irrigating chopper directs the flow and movement of cataract material toward the safe zone in the center of the eye. Both of these surgeon-controlled bimanual irrigation techniques are vastly different from the unorganized, random, and variable irrigation properties of coaxial phaco, as the combined instrument is rotated and moved around inside the eye.

Another key feature of MICS sleeveless phaco is the ability to withdraw the phaco aspiration instrument into the wound or even completely out of the eye without losing chamber stability. This is helpful when there is cataract material close to the wound. If a coaxial instrument is pulled back toward the wound, the irrigation ports get blocked in the wound and the chamber collapses suddenly. This is one of the common causes of posterior capsular tears with coaxial phaco. The separate irrigation in MICS maintains a deep chamber regardless of the position of the phaco instrument.

Cortical cleanup with bimanual irrigation and aspiration is also advantageous because the instruments can be interchanged in the wound to allow better access to subincisional and hidden cortex. Again, the aspiration port can be pulled back very close to the wound without loss of chamber depth because of its independence from irrigation.

There are other more subtle advantages to a smaller-incision procedure that surgeons appreciate after transitioning to MICS. For example, during capsulorrhexis formation with a coaxial 3.0 mm wound, often viscoelastic will leak out of the eye, leading to some loss of chamber depth and a greater tendency for a peripheral tear in the anterior capsule. In MICS, there is little opportunity for viscoelastic to escape from the eye. The chamber stays deep, the anterior capsule remains flat, and it is easy to perform a controlled and customized capsulorrhexis. A microcapsulorrhexis forceps can both tear and grasp the anterior capsule with precise surgical control.

Many surgeons who are proficient in coaxial and bimanual surgery feel that challenging cases, such as those with small pupils, floppy iris, pseudoexfoliation syndrome, and traumatic cataracts, are considerably easier with the bimanual technique, and that the technique creates a more controlled and predictable environment inside the eye. In cases where an anterior vitrectomy is required, separating the irrigation from the cutting and aspiration is also advantageous. The irrigation handpiece can be directed into the anterior chamber while cutting, and aspiration can be performed in the vitreous cavity This reduces vitreous hydration and the prolapse of additional vitreous forward. Irrigating in the anterior chamber while phacoemulsifying deeper in the eye pushes the iris posterior and away from the wound. This can reduce iris movement, damage, and entrapment in the wound.

More advantages and applications of MICS are sure to come to light as surgeons continue to gain experience with the technique. The continued advancements in phacoemulsification instruments and technology, coupled with the availability of microincisional implants, will likely drive the gradual transition toward this sophisticated technique for cataract removal.

References

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4. Braga-Mele R, Liu E. Feasibility of sleeveless bimanual phacoemulsification with the Millennium microsurgical system. J Cataract Refract Surg. 2003;29(11):2199-2203.

5. Jeng B, Huang D. Anterior chamber stability during bimanual irrigation and aspiration. J Cataract Refract Surg. 2001;27(10):1670-1678.

6. Tsuneoka H, Shiba T, Takahashi Y. Feasibility of ultrasound cataract surgery with a 1.4mm incision. J Cataract Refract Surg. 2001;27(6):934-940.

7. Soscia W, MD, Howard JG, Olson RJ. Bimanual phacoemulsification through 2 stab incisions: a wound-temperature study. J Cataract Refract Surg. 2002;28(6):1039-1043.

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Author Disclosure

Dr. Weinstock states that he has no financial relationship with the manufacturer or provider of any product or service discussed in this article or with the manufacturer or provider of any competing product or service.