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EW RESIDENTS 104 October 2018 by Liz Hillman EyeWorld Senior Staff Writer YES connect surements on virgin eyes that have not had drops or pressures checked, in addition to modern formulas like the Barrett and Hill-RBF, result in accurate axis recommendations. He marks the patient's 180 axis at the slit lamp and takes note of limbal landmarks, and relies on a picture the LENSTAR (Haag-Streit, Koniz, Switzerland) produces, which he brings to the OR. Both he and Dr. Baartman said they use a smartphone leveling app that helps them confirm accurate positioning of their toric marks. There are several intraoperative steps that could help maintain IOL stability. One includes using a cap- sular tension ring (CTR) in certain circumstances. Dr. Safran said he is quick to use a CTR in patients who are myopic with with-the-rule astigmatism. "Usually, my cutoff is about 26.5 mm, if I'm going with-the- rule," Dr. Safran said. "If it's against- the-rule, I don't bother with a CTR unless it's a big eye, 29.5–30 mm. I tend to avoid using torics for low with-the-rule astigmatism in ex- tremely large eyes, unless there is a because the zonules are in good shape, they're less likely to bunch up around the haptics," Dr. Safran said. "The capsular bag, if it's tighter, if the zonules are in great shape, it's less likely to bunch up around the haptics than if the zonules are loose. By the same token, the stiffer the haptics of the lens, the more likely there is to be rotation. If you had stiff haptics and a stiff capsular bag, you'd be more likely to see rotation than if the haptics were soft and if the bag was soft." Preventative measures The first step to optimal toric IOL performance is placing it on the cor- rect axis to begin with. Dr. Baartman said he will mark patients at the 6 o'clock limbus preoperatively while they're sitting up, but will place more weight on an intraoperative aberrometer's reticle to identify the eye's true axis of cylinder. In contrast, Dr. Safran said he doesn't use intraoperative aberrome- try, thinking that it's not as accurate compared to preoperative measure- ments, among other reasons. He finds conducting preoperative mea- How to manage toric IOL rotation postoperatively and preventative measures to take intraoperatively T he importance of a toric IOL being placed—and remaining—at the appro- priate axis is critical for optimal performance. A frequently cited study describes how just 1 degree of misalignment results in 3.5% of residual cylinder; 3 de- grees of misalignment in 10.5% of residual cylinder; and 30 degrees of misalignment in a total loss of the toric's astigmatic correcting effect. 1 How common is toric IOL rotation? Steven Safran, MD, New Jersey Surgery Center, Lawrenceville, New Jersey, said he thinks it's "not that uncommon to see 5–10 degrees of rotation with toric lenses." Knowing methods to reduce the risk of IOL rotation in eyes more susceptible to it and how to manage residual astigmatism after rotation occurs is important. Still, the opin- ions on management of a rotated toric IOL vary. Who's at higher risk? A toric lens can rotate out of posi- tion, especially within the first few postoperative hours, in any patient, but there are eyes more at risk than others, said Dr. Safran and Brandon Baartman, MD, Vance Thompson Vision, Omaha, Nebraska. "Identifying those eyes pre- operatively can often help guide intraoperative strategies to reduce that postoperatively," Dr. Baart- man noted, sharing that he thinks higher-risk eyes are those with larger axial lengths and white-to-white distances. "They have a little more room inside the eye and in the bag for postoperative lens rotation." Dr. Safran also finds that axial myopes with larger capsular bags are more at risk for toric lens rotation, as are patients with with-the-rule astigmatism where the lens is placed from 6–12 clock hours. He also said those with healthier zonules are more likely to see toric rotation. "Let's say you're going to slide on the floor, like a baseball player, and if the rug you're sliding on is tacked down tightly, you're going to slide further than if that rug was loose. If the capsular bag is tight Toric IOL rotated—now what? T oric intraocular lenses are a wonder- ful option for people with pre-existing corneal astigmatism undergoing cataract surgery. Precision is key, and there are multiple steps along the way where errors can occur that can ultimately lead to residual astigmatism. This month's column discusses the steps to take when you have identified a toric IOL that has rotated, who is at particular risk for rotation, and how to mitigate that risk. It is important to consider other possible sources of error when placing a toric lens including the magnitude and axis of astigmatism based on topography or biometry, how accurate your marking is, and whether or not the lens is in the exact place you left it. There are a number of tools available to help with accurate mark place- ment including specialized instruments, intraoperative aberrometry, and even apps. Some surgeons will utilize high resolution photography to compare the axis to promi- nent vessels and other structures in the eye to serve as a guide. For those of you in training, I recom- mend that you implant a number of toric IOLs during your training program. Not only is it a good option for your patients, it is important to be comfortable with all aspects of these lenses, including the discussion before surgery and the postoperative care. I would also encourage you to be obsessive about the numbers and your results and to explore every reason you may not be getting an emmetropic outcome. Samuel Lee, MD, YES connect co-editor Intraoperative photo of Symfony toric lens (Johnson & Johnson Vision) undergoing rotation by 16 degrees. Limbal marks are made with use of a Mendez ring, one where the toric marks are currently sitting and the other 16 degrees away. Note that the cornea is dried thoroughly to ensure proper inking at the intended mark. Source: Brandon Baartman, MD

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