The Soft Touch
Can irrigation/aspiration tips made from silicone help reduce capsular complications during cataract surgery?
Garry Condon |
At a Glance
- Posterior capsule tears during cataract surgery are commonly very problematic
- You’re more likely to induce them during I/A in patients with ocular issues like weak zonules – but it can happen even in “regular” cases
- Using a silicone I/A tip rather than a metal or plastic tip may help to minimize capsular rupture and provide easier IOL rotation
- Preconfigured single-use silicone I/A tip systems may help to not only minimize the risk of trauma to the capsular bag but also eliminate tricky (and often unpredictable) tip assembly
For many of us, cataract surgery is best described as a high-volume surgery. Today, clinics are busy; the patient lists are long, and one consequence is that you will see even relatively rare complications fairly often. Inevitably, these will include patients with pseudoexfoliation syndrome, who have weak zonules and therefore very lax capsular bags. This means that there’s an increased risk of aspirating the capsular bag into the irrigation/aspiration (I/A) tip during the procedure and tearing the delicate posterior capsule – although this is by no means a complication that only happens with lax capsular bags; it’s something that can still occur even in “routine” cases (1).
The bad touch
One contributing factor can be the I/A tip, which can be fabricated from three types of material: metal, plastic or silicone, with the “friendliness” to the capsular bag increasing, respectively, with each material. Minor imperfections in the metal tip can cause the posterior capsule to tear, whereas non-metal materials, like plastic and silicone, are better in this regards, with silicone I/A tips having the advantage over more rigid plastic I/A tips in that they can be shaped and angled too – and that’s something that I and many other surgeons appreciate.
As a measure of just how “capsule-friendly” silicon I/A tips are, let’s examine the findings from a retrospective chart review of all patients who had cataract extraction by phacoemulsification by third-year ophthalmology residents at the Parkland Memorial Hospital in Dallas, Texas. Of the 1,072 cases performed with a metal I/A tip, there were 13 cases of vitreous loss during cortex removal (a rate of 1.2 percent); 26 percent of all vitreous loss during that time occurred during cortex removal. Of the 805 cases performed with a silicone I/A tip, there was only one case (0.1 percent) of vitreous loss during cortex removal (p=0.004); only 4 percent of all vitreous loss during that time occurred during cortex removal (p=0.011) (2).
A light touch
The gentleness of single-use, silicone I/A tips, and the ease with which you can polish the capsule has come with some drawbacks – the silicon present reduces the diameter of the I/A hole, and this can result in a longer duration of OVD removal (or at least, it requires you to use higher aspiration rates). Furthermore, silicon tips are thought to require more careful handling and are costlier than their metal-based counterparts.
The single-use I/A tip I use (Allegro, MST, Redmond, WA), has an aspiration tube that’s completely encased within the silicone tip and its upstream opening, meaning that it’s very unlikely that the capsular bag will be traumatized or aspirated into the tip. Further, the silicone portion of the external sleeve has a generous opening and volume for irrigation fluid to flow – minimizing one of the biggest drawbacks of traditional silicone I/A tips.
One of the things that we’ve all struggled with is the unpredictability of I/A tips that have to be assembled in the operating room. Sliding the sleeve over a metal tip can be challenging and often has to be repeatedly adjusted by a technician. One of the benefits of a single-use I/A tip is that it is already fully assembled and pre-adjusted as a single piece that can be placed on the hand piece with just a half a turn by the operating technician so that the sleeve and the port are in perfect alignment. So long as the technician handles the tip in the right way, they (and you) shouldn’t experience any problems with it. It’s a time-saving feature, and thankfully several manufacturers are starting to develop preconfigured I/A tips.
Getting a grip
The tip that I use has a 45° angle, making it easy to manipulate the intraocular lens (IOL) in situ under a little bit of aspiration – you get a good grip and it means it’s easy to rotate the lens – something that’s rather useful, for example, when you’re using a toric lens. I also find that, because the tip is tapered, it is easy for me to get just past and behind the edge of the IOL in order to aspirate any residual viscoelastic – something that is particularly important when placing a toric IOL, as the lens needs to sit against the capsular bag. Lastly, because of the tip’s generous infusion quantity, I find that I can stop within the incision on my way out, add in the irrigation mode, and hydrate the incision to the degree that by then extracting the tip in a quick motion, I get a virtually self-sealed incision.
Ultimately, there are many things to consider when choosing an I/A tip for your phacoemulsification system: price, compatibility, availability, familiarity… the list is long. But I’m convinced that in terms of material, safety, speed and ease-of-use, preconfigured single-use silicone I/A tip systems offer tremendous advantages to me, my colleagues, and ultimately, our patients over their metal and plastic counterparts.
- GS Ang, IF Whyte, “Effect and outcomes of posterior capsule rupture in a district general hospital setting”, J Cataract Refract Surg, 32, 623–627 (2006). PMID: 16698484.
- PH Blomquist, AC Pluenneke, “Decrease in complications during cataract surgery with the use of a silicone-tipped irrigation/aspiration instrument”, 31, 1194-1197 (2005). PMID: 16039497.