An I/A tip system comprises a preassembled, single-use silicone I/A tip, which has advantages over other commercially available products. It helps to reduce capsular rupture during cataract surgery and also eliminates tricky tip assembly and cleaning.
Reviewed by Johan Blanckaert
Take-home: The Allegro I/A tip system comprises a preassembled, single-use silicone I/A tip, which has advantages over other commercially available products. It helps to reduce capsular rupture during cataract surgery and also eliminates tricky tip assembly and cleaning.
During phacoemulsification, it is necessary to aspirate material and supply irrigation fluid. Unfortunately, some irrigation/aspiration (I/A) devices may cause posterior capsular rupture. Surgical technique is key in preventing capsular rupture: for example, it is possible to reduce the risk of a posterior capsular tear by positioning and maintaining the I/A tip anterior, rather than posterior, to the IOL.1
Evidence suggests that the material from which the I/A tip is made can also be important. Interestingly, research published more than 30 years ago reported a case of posterior capsular rupture following the use of a new hard I/A tip. Using scanning electron microscopy of the tip, the authors observed burrs on the aspiration portion of the tip as well as poor finishing around the irrigation ports.2
A study undertaken at the University of Texas Southwestern Medical Center, Dallas, USA showed that use of a silicone I/A tip reduces the risk of capsule rupture.3 The study found that the overall incidence of vitreous loss during cortex removal was significantly decreased using a silicone- rather than a metal-tipped I/A instrument. Of the 1072 cases that used a metal tip, 13 (1.2%) experienced vitreous loss during cortex removal; 26% of all vitreous loss occurred during cortex removal. Of the 805 cases that used a silicone tip, there was only a single case (0.1%) of vitreous loss during cortex removal (p=0.004) and only 4% of all vitreous loss occurred during cortex removal (p=0.011).3
A preassembled silicone I/A system
There are a number of silicone I/A tip systems now available. Some are reusable, some disposable and some a combination of both. I use the Allegro I/A silicone-encapsulated tips in conjunction with the Allegro handpiece (MicroSurgical Technology, Inc., Redmond, WA, USA). While the handpiece is designed to be reusable, the tips are for single use.
The Allegro I/A tip system has several advantages over other systems. Not only is it capsule friendly, the tip comes preassembled, thus eliminating the need to fit a sleeve. Two bends in the tip provide improved access to the subincisional cortex with less torque on the wound, while the irrigation port is optimised for working close to the wound. The Allegro I/A tip also permits easy IOL rotation.
Courtesy of MicroSurgical Technology Inc.There are a number of reasons why I use the Allegro I/A tip system. First, I wanted to use something soft, rather than hard metal, to avoid wear and small burrs at the tip, which can rupture the posterior capsule. The second advantage for me is the fact that the tip comes preassembled, which saves time and errors in assembly. Reusable silicone tips exist but are notoriously difficult to clean, with cortex particles, which can pass to the next patient, being retained in the tip. I am uncomfortable with this and prefer a single-use system.
Another point is that the Allegro I/A tip system is good for all cases, including standard and femtosecond-laser cataract surgery. Some doctors are a little intimidated by femtosecond-laser cases because the cortex is cut at the same level as the anterior capsule: they have to reach further in order to get the cortex. This can be difficult with some tips, but the Allegro has just the right amount of curve. Also, if there is a piece of cortex stuck to the posterior capsule, it is possible to use the silicone tip to peel it off. You might see the capsule wrinkle a little, but it won’t tear.
The only downside to the Allegro is that it is designed to be used with an incision of 2.2 to 2.4 mm: with a larger incision, there tends to be a little egress of fluid. However, I believe that MicroSurgical Technology is developing a larger tip for surgeons who use incisions greater than 2.4 mm. Overall, this system has solved most of the problems we have had with previous tips, which is why I use the Allegro I/A tip system for around 80% of my cataract procedures.
1. B.W. Sim et al., Clin. Experiment. Ophthalmol. 2013; 41(5): 450-454.
2. C. Reed-Miller, K.B. Heslin and S. Liebowitz. J. Am. Intraocul. Implant. Soc. 1985; 11(4): 391-392.
3. P.H. Blomquist and A.C. Pluenneke. J. Cataract Refract. Surg. 2005; 31(6): 1194-1197.
Dr Keith Walter
Keith Walter, MD, is a professor of ophthalmology at Wake Forest Baptist Medical Center, North Carolina. Professor Walter has no financial interests in MicroSurgical Technology, Inc.