EyeWorld Today is the official daily of the ASCRS Symposium & Congress. Each issue provides comprehensive coverage editorial coverage of meeting presentations, events, and breaking news
Issue link: https://daily.eyeworld.org/i/124056
6 EW San Francisco 2013 Monday, April 22, 2013 Toric IOLs: Are they all the same? by John Berdahl, MD Toric lens success depends on stability John Berdahl, MD " The AcrySof lens material has a unique 'tackiness' and has been shown to have greater fibronectin binding than other IOL materials … This bond between the anterior and posterior capsule helps to stabilize the lens in place and contributes to the rotational stability of the lens. " Toric IOLs are an ideal option for astigmatic cataract patients with .75 D of corneal astigmatism or greater. They address a known problem, one that is intuitive and logical to patients. Just as I would not prescribe spectacles to patients without correcting astigmatism, it would make no sense to me not to offer a toric lens to my cataract patients. Toric lenses are more predictable than limbal relaxing incisions (LRIs) or astigmatic keratotomy (AK) in patients with more than 0.75 D of astigmatism. Incisional techniques have a less predictable healing response, and (if using a manual LRI technique) surgeons need to consider the variability in incision depth, arc, and angulation. The AcrySof* IQ toric IOL (Alcon, Fort Worth, Texas) features the aspheric technology and refractive clarity of the AcrySof platform. Its excellent rotational stability makes treating corneal astigmatism in cataract patients very simple. Rotational stability, lens placement There cannot be enough emphasis on how crucial rotational stability is in a toric lens. The AcrySof lens material has a unique "tackiness" and has been shown to have greater fibronectin binding than other IOL materials, which promotes adhesion to the capsule (Figure 1).1 This bond between the anterior and posterior capsule helps to stabilize the lens in place and contributes to the rotational stability of the lens.2 Delivering the lens in the capsular bag is equally important. We want a lens that's flexible enough to be easily positioned to align on the axis. At the same time, we want a lens that is stable enough that the contraction forces of the capsular bag won't vault or distort the lens. The AcrySof platform is a nice balance between these two features. The single-piece platform's combination of material and Stableforce haptics keep the AcrySof IQ toric lens stable and centered in the capsular bag, while the flexible haptic design allows for optimal placement in the bag, regardless of size. Figure 1 Source: Alcon Unfolding of the haptics An aspect of the AcrySof platform I particularly appreciate is the speed at which the haptics open in the bag. Surgeons have the appropriate time (about 10-20 seconds) to manipulate the lens into its rough position before it is fully unfolded; those of us using intraoperative aberrometry to refine outcomes enjoy that the lens unfolds relatively quickly. One pearl: Ensure the haptics are entirely unfolded when the case is finished, and completely remove the viscoelastic from behind the IOL. Then just "tap" the center of the lens posteriorly, so there is contact between the posterior capsule and the lens. If a surgeon realizes in the OR the lens has not been properly aligned, my advice is to put a little viscoelastic under the lens, and rotate (always clockwise as the haptics move more freely in that direction) the lens to the proper position. Clinical pearl: Finding the ideal axis Finding the ideal axis is the most important and sometimes the most challenging aspect of toric IOL implantation. Although this does not occur often, sometimes the lens is exactly where we intended to place it—but that location is not the ideal axis. Differentiating between the intended and ideal axis is necessary for these lenses. If there is residual astigmatism postoperatively, there are two options: perform laser vision correction or return the patient to the OR and rotate the lens. David Hardten, MD, and I developed an online tool that is hosted by ASCRS that can help surgeons, www.ascrs.org/toricresults-analyzer. Surgeons input the manifest refraction, what toric lens is being used and its axis, and the site will calculate where the lens should be rotated to and estimate the new refraction. The key issues for surgeons to consider are whether the spherical equivalent is acceptable and whether the residual astigmatism is acceptable. I personally find that anything under 0.50 D of residual astigmatism is usually not noticeable to patients. A quality lens platform In my hands, the AcrySof IQ toric lens tackles some of the most challenging issues of toric lenses through its material and design, and produces great alignment, adhesion to the bag, and most importantly, excellent rotational stability. As we continue to advance into more sophisticated toric lenses and multifocal torics, I believe this lens platform will evolve seamlessly with us. *AcrySof is a trademark of Novartis. References 1. Linnola RJ, Sund M, Ylonen R, et al. Adhesion of soluble fibronectin, laminin, collagen type IV to intraocular lens materials. J Cataract Refract Surg. 1999;25:1486-1491. 2. Linnola RJ. Sandwich theory: Bioactivitybased explanation for posterior capsule opacification. J Cataract Refract Surg. 1997;23:1539-1542. Dr. Berdahl is in private practice, Vance Thompson Vision, Sioux Falls, S.D. He can be contacted at 605-328-3937. Please refer to page 8 for important safety information about the Alcon products described in this supplement.