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Tooling up for glued IOLs: Significance of three-piece IOLs and injectors
Good IOL implantation relies on the material and design of the lens and the type of injector.
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IOLs and their respective materials and designs are intended to be inert and made in a way so that they are easy to handle concerning the folding-unfolding aspect and implantation into the eye. The importance of the overall length of an IOL for intrascleral haptic fixation cannot be understated. Along with the length of the IOL, the shape, configuration and material of the haptics are equally important. The smoothness with which the IOL unfolds and presents itself in the eye is also crucial. The type of IOL used and the kind of injector employed for unfolding the IOL intraocularly are of equal concern.
Materials and design
A three-piece IOL is preferred and recommended for glued intrascleral haptic fixation. The main issue with a one-piece IOL is the difficulty incurred in externalizing the haptics because the haptics are not flexible and tend to break easily. A foldable or non-foldable three-piece IOL can be easily employed in the glued IOL technique; the disadvantage with the non-foldable three-piece IOL is that a larger incision is required to introduce the IOL as compared with the foldable counterpart, but the non-foldable IOL has fewer chances of optic capture because it has an optic diameter of 6.5 mm as compared with a foldable IOL that has a 6-mm optic.
The material employed for making the haptic of the IOL is most commonly PMMA, polyvinylidene fluoride (PVDF), polyamide (Elastimide) or polypropylene (Prolene). Prolene haptic material has a lower memory as compared with the other materials and is used less frequently. Compared with a J-loop, a C-loop or a modified C-loop configuration of the haptic is preferable because the haptics tend to curve and align according to the curvature of the globe.
Image: Narang P, Agarwal A
The injector employed for IOL unfolding also has a significant role in the glued IOL technique because it signifies the proper control and slow unfolding of an IOL. An injector system with good control over IOL unfolding is always preferable, and especially in cases of a glued IOL, it prevents abrupt unfolding and minimizes the chances of IOL drop on the OR table because there is no posterior capsule to support the IOL.
A three-piece IOL with a modified C-loop haptic configuration and an overall length of at least 14 mm is desirable and would be ideal for intrascleral haptic fixation. Having an IOL with long haptics facilitates a sufficient amount of haptic tuck into the scleral tunnel, especially in large eyes with a greater white-to-white diameter.
IOLs
Abbott Medical Optics has a hydrophobic foldable three-piece IOL with an overall length of 13 mm, PMMA haptics and an optic diameter of 6 mm. The Abbott injector is most aptly suited for twisting, injecting and slow unfolding of an IOL (Figures 1 and 2). The only drawback is that it requires an assistant to slowly twist the injector handle and assist in unfolding. Abbott also offers a three-piece multifocal IOL that can be employed in glued IOL surgery (Figure 3).
The Bausch + Lomb injector has a plunger push mechanism with the advantage that the surgeon can slowly inject the IOL without the need of an assistant to twist the rear end of the injector (Figure 4). Bausch’s IOLs are made up of silicone and should be used cautiously in highly myopic eyes, which may have a propensity to develop retinal detachment in the future because the optics of these IOLs tend to imbibe and opacify when they come in contact with silicone oil. These IOLs have recently been discontinued in India.
Alcon has a hydrophobic foldable three-piece IOL with a 6-mm optic, overall length of 13 mm and PMMA haptics with a modified C-loop configuration. The unfolding of an Alcon IOL may be abrupt and jerky (Figures 5 and 6). We recommend that if the surgeon uses an Alcon IOL, the Abbott injector works well with it, giving good control of IOL unfolding.
The Aaren IOL is also a three-piece with a hydrophobic acrylic component but with resilient PVDF haptics. These haptics are known to give better control and manipulation with fewer tendencies toward a kink in the haptics or haptic breakage.
STAAR IOLs have an overall length of 14 mm, which is ideally suited for glued IOL fixation. They have polyamide haptics with a silicone optic of 6 mm in diameter. STAAR IOLs have also been noted to be jerky with less control when unfolding. Unfortunately, STAAR and Aaren IOLs are currently not available in India, but surgeons in other parts of the globe can avail their advantages.
Guidelines
While unfolding an IOL, the surgeon should take care of the method in which the haptic and IOL behave when they eject from the tip of the cartridge. We described a “lucky 7 sign” (Figure 1), the term being coined by Tom Oetting, in which the track of the leading haptic in the cartridge is assessed, noticing for any kink or any other unusual presentation of an IOL before injecting the IOL in the eye.
Another important clinical point involves the extrusion of the tip of the leading haptic from the cartridge before introducing the cartridge in the eye (Figure 1). This again ensures proper unfolding of the IOL and also facilitates catching the tip of the leading haptic in the glued IOL surgery from the sclerotomy site with the help of end-opening forceps.
- For more information:
- Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; email: dragarwal@vsnl.com; website: www.dragarwal.com.
- Priya Narang, MS, is the director of Narang Eye Care & Laser Centre, Ahmedabad, India. She can be reached at email: narangpriya19@gmail.com.
Disclosures: The authors report no relevant financial disclosures.