Experience with a preassembled silicone I/A tip during cataract surgery
Every ophthalmologist requires precise surgical tools with which he or she can perform surgery safely and accurately in order to ensure optimal outcomes. The availability of high-quality microsurgical instruments has increased over the past decade with manufacturers continually modifying and optimising existing instruments.
Every ophthalmologist requires precise surgical tools with which he or she can perform surgery safely and accurately in order to ensure optimal outcomes. The availability of high-quality microsurgical instruments has increased over the past decade with manufacturers continually modifying and optimising existing instruments. Even small modifications to an instrument can lead to significant intraoperative and postoperative improvements.
There are a number of silicone I/A tip systems available. The silicone irrigation/aspiration (I/A) tip (Allegro) is a microsurgical instrument that allows the surgeon to safely remove cortical material during cataract surgery. It also allows the user to polish the posterior capsule, and rotate or adjust the placement of the IOL, which is particularly useful when implanting and positioning a toric IOL.
During cataract removal, the lens nucleus is hydrodissected and emulsified using ultrasound and, on occasion, assisted by a chopper or spatula which is inserted through a side port. After phacoemulsification of the lens is completed, an I/A system is used to aspirate the cortical material.
At the end of this procedure, it is possible for fragments of the lens nucleus or cortex to remain in the capsular bag. It is imperative that these fragments are completely eliminated since retained nuclear or cortical material may lead to severe inflammation, secondary glaucoma, and may also distort the IOL’s position.
Removing cortical fibers and fragments without damaging the delicate capsular bag is a fine art that requires not only skill and experience, but also an optimally designed I/A system.
A tissue-friendly I/A tip
There is a silicone I/A system (MST Allegro, MicroSurgical Technology, Inc, Redmond, WA, USA) that combines silicone encapsulated tips in conjunction with the Allegro hand piece. The hand piece is designed to be reused (following cleaning and sterilisation), but the tips are for single use only and are disposed of following surgery.
The Allegro tips are completely covered with silicone, leaving no sharp edges and providing safer irrigation and aspiration. Specifically, the silicone sleeve minimises the risk of injury to the capsule, which can sometimes occur with metal-tipped I/A instruments.
The aspiration and irrigation ports are also smooth/polished for enhanced capsule protection. The tip comes preassembled, thus eliminating the need to install a sleeve.
Study findings
The superiority of a silicone versus a metal I/A tip was demonstrated in a retrospective study undertaken at the Parkland Memorial Hospital in Dallas, Texas, USA. All cataract surgeries performed between September 2000 and February 2004 were evaluated.
In total, 1,072 cases were performed using a metal I/A tip. In this group, there were 13 cases of vitreous loss (rate of 1.2%). In the 805 cases performed using a silicone I/A tip, there was only one case of vitreous loss (rate of 0.1%)1.
Expert opinion
There are several design benefits to the Allegro I/A tip system. During movements that bring us toward the anterior capsule leaflet, it is possible to accidentally apply suction to the wall of the capsule. If the aspiration port is metal or plastic, it may have sharp or uneven edges that can tear or damage the thin wall. This may lead to complications that we want to avoid.
The Allegro I/A tip provides, in this regard, a much higher level of safety. The aspiration port is soft, smooth and rounded making it highly tissue-friendly. One can use this tip to directly approach the posterior capsule wall without damaging it. It’s an ideal instrument for both beginners and experienced surgeons.
The unique geometry of this tip features two bends which improve access to the subincisional cortex while minimising torque on the wound. Additionally, the irrigation ports are distally located, which is optimised for working close to the wound.
While there are other silicone I/A tips available, some require assembly, i.e., it is necessary to install the silicone sleeve over the tip. If the tip is not assembled correctly or the silicone cuff shifts during surgery, there is a risk that the ports will not be totally encased in silicone. In such cases, small burrs that may occur in the metal could make contact with the capsule and risk damaging it.
The Allegro I/A tip is completely configured for a single use. It is taken from the packaging, bolted with a half twist on the handpiece and is ready for use.
Reference
1. Blomquist PH, Pluenneke AC. Decrease in complications during cataract surgery with the use of a silicone-tipped irrigation / aspiration instrument. J Cataract Refract Surg. 2005;31:1194-1197.
Dr Christoph Binder
E: christoph.binder@schwarzwaldaugenklinik.de
Dr Christoph Binder is medical director at the clinic Schwarzwaldaugenklinik. He has studied at the Universities of FU Berlin, LMU Munich and at the Ludwig-Maximilians-University Munich, focusing on retinal diseases. Now he specialises in refractive surgery.
