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Up Front | Sep 2007

Microphacoemulsification Techniques

Why I believe coaxial sleeved has beat out bimanual sleeveless in the United States.

Few procedures in cataract surgery have been so thoroughly promoted as bimanual sleeveless microphacoemulsification. Despite the tabloid headlines and 5 years of media saturation, however, only a fragment of cataract surgeons has bought into this technique. The reasons are quite obvious.

First, the fluidics of bimanual sleeveless microphacoemulsification are downright unfavorable. A 22-gauge (Agarwal), 21-gauge (Olson), 20-gauge (Fine), or 19-gauge (Steinert) irrigating chopper does not allow enough infusion to stabilize the anterior chamber. Even when the bottle height is elevated to the roof, the surgeon cannot work at his/her usual vacuum levels and aspiration rates without experiencing surge because of excessive leakage around both the unsleeved phaco needle and irrigating chopper. The consequences of working at lower levels of vacuum with a 0.9-mm phaco tip create a trade-off in purchasing power and overall efficiency. Contrary to vociferous claims, bimanual microphacoemulsification is by no means a quick operation.

The second drawback of this technique deals with the integrity of the incision. When a round metal tube is manipulated through a tight linear incision, the opening changes architecturally. Trying to put a metal tip through a tight incision will dramatically increase stress at the corners of the incisions, which may prevent it from sealing. By contrast, an infusion sleeve around the needle reduces incision stress by an order of magnitude.1 Microincisions leak, further compromising chamber stability, and several studies by Douglas Koch, MD,2 of Houston; Abhay Vasavada, MD, FRCS,3 of Ahmedabad, India; and Terry Kim, MD,4 of Durham, North Carolina; have confirmed collagen damage within the incision. In fact, excellent surgeons such as I. Howard Fine, MD, of Eugene, Oregon, routinely make a third incision for the IOL, because they cannot depend upon the competency of the primary incisions. Renowned surgeon Richard L. Lindstrom, MD, of Minneapolis, solved chamber instability with an additional incision for an anterior chamber maintainer to improve chamber stability. However, when one adds up the incisions (1.2 mm + 1.2 mm + 2.7 mm), the sum total is more than 5 mm—not microphacoemulsification, but rather macrophacoemulsification!

SAFETY ISSUES WITH BARE NEEDLES
Additional safety issues of sleeveless microphacoemulsification must also be addressed. For example, there is almost no margin of safety against a thermal injury when a bare phaco needle is within a tight corneal incision. Fortunately, Advanced Medical Optics, Inc. (Santa Ana, California), introduced the WhiteStar phaco system, which uses hyperpulse with a duty cycle for a thermoprotective effect (now available on all machines). Nevertheless, the system's primary source of cooling is aspiration through the needle, and the chance of the 0.9-mm needle becoming plugged with a viscoelastic material at low vacuum, could be problematic.

PROBLEMS WITH IOLs
The IOL issue is also presently at a disadvantage. In the United States, there is no IOL approved for microincisional surgery, which means that the American surgeon must enlarge the incision anyway. Surgeons outside the United States may have the advantage of implanting an IOL through a tiny incision, but must ask if it is wise to sacrifice many of the sophisticated advances in IOL technology just to get through a smaller incision. Compromising a superior material, a low rate of posterior capsular opacification, macular protection, aberration reduction, toric correction, and multifocality—which are all presently available—simply does not make sense. Granted, this argument will disappear as a new generation of quality microincision lenses is introduced.

LEARNING CURVE
Finally, a steep learning curve has prevented a vast majority of cataract surgeons from embracing bimanual sleeveless microphacoemulsification. This operation is definitely different than a routine phacoemulsification technique. In fact, nearly every step is different, (eg, capsulorrhexis, emulsification, bimanual cortical removal). Although an experienced surgeon like Jorge L. Alió, MD, PhD, of Spain, is capable of performing this procedure with superb results, my patients did not enjoy the excellent UCVA and the consistent corneal clarity that was published by three of my fellows in the Journal of Cataract and Refractive Surgery.5 In a more recent study presented at the 2007 American Society of Cataract and Refractive Surgery (ASCRS) meeting by Fabio Vaz, MD,6 98% of patients attained a UCVA of 20/40 or better on postoperative day 1, following microcoaxial phaco with torsional ultrasound. Sixty-two percent enjoyed 20/20 or 20/25 unaided vision. I honestly admit that I could not duplicate my coaxial results with a bimanual sleeveless technique, despite my best effort and many trips to the practice lab.

The drawbacks of bimanual sleeveless microphacoemulsification have motivated the industry to develop microincisional cataract technology with improved criteria for efficacy, safety, and IOL facility. It was with great excitement in 2004 that I accepted an invitation from Alcon Laboratories, Inc. (Fort Worth, Texas), to investigate a new generation of phaco sleeve technologies. The Ultra Sleeve (Alcon Laboratories, Inc.) was developed for coaxial phacoemulsification using either a 0.9-mm or a 1.1-mm flare tip through a 2.2-mm incision (Figure 1). The laboratory evaluation my colleagues and I conducted yielded outstanding results.7 We found that infusion flow rates were approximately 60% greater than those measured with irrigating choppers, and incision temperatures were recorded at 20% lower when comparing the same parameters using sleeveless bimanual phacoemulsification. We also found the incisions to be consistently more competent (Figure 2), and we measured approximately seven times less wound leakage than during bimanual sleeveless microphacoemulsification. Furthermore, surge testing confirmed greater chamber stability with the Ultra Sleeve during coaxial phacoemulsification.

Fortified with such positive laboratory results, I began using coaxial microphacoemulsification with the Infiniti machine (Alcon Laboratories, Inc.) 3 years ago and have continued to use this technique, adding torsional ultrasound for all of my patients.8 It has virtually no learning curve and features marvelous fluidics. The only modification it requires is a slightly higher bottle height and an altered technique for inserting the IOL. The torsional action is also enhanced by use of a Kelman or curved tip (I have designed an 11º curved tip with Alcon Laboratories, Inc. which is in the evaluation phase). I use the same chopping method within the capsular bag to disassemble the nucleus and then I remove the cortex with the unparalleled safety of the silicone I/A tip. I can inject a full-sized 6-mm AcrySof SN60 WF, toric, or ReStor IOL (all manufactured by Alcon Laboratories, Inc.) through a 2.2-mm incision by using a second instrument to provide countertraction in the stab incision (Figure 3). This modified technique requires loading the lens like the picture on the cartridge for bevel-down insertion within the incision (Figure 3). The lens is advanced within the cartridge by the plunger of a one-handed injector, and the IOL will open like a book within the ophthalmic viscoelastic device (OVD). The haptics are easily positioned within the capsular bag using an Osher Y-hook (MP205; Duckworth & Kent Ltd., Hertfordshire, England). The incision is hydrated before I remove the OVD; then it remains consistently competent at the end of the operation (Figure 4).

CONCLUSION
Coaxial microphacoemulsification is an excellent approach to small-incision surgery and has taken its rightful place in the evolution of cataract surgery. Surgeons are transitioning from their current technique easily, as the procedure's fluidics are almost identical to the safe intraocular environment to which we have become accustomed. Combined with torsional ultrasound, surgeons are witnessing increased efficiency with less repulsion and chatter of nuclear material. Reproducible injection of a superior IOL with superb centration can be achieved without either enlarging or making a separate incision. Furthermore, patients' UCVA and corneal clarity on postoperative day 1 are enormously satisfying to both the surgeon and patient alike. Although I could not endorse bimanual sleeveless microphacoemulsification, I did predict the rapid acceptance of this new microcoaxial technology, and I am proud to have had the opportunity to share the laboratory science and our clinical results with my colleagues.

Robert H. Osher, MD, is a Professor in the Department of Ophthalmology, University of Cincinnati College of Medicine, and Medical Director Emeritus of the Cincinnati Eye Institute. He is also the Founder and Editor of the Video Journal of Cataract and Refractive Surgery. He states that he is a paid consultant to Alcon Laboratories, Inc. Dr. Osher may be reached at +1 513 984 5133; rhosher@cincinnatieye.com.

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