EyeWorld India March 2019 Issue

36 March 2019 EWAP CATARACT / IOL Toric IOL rotated—now what? by Liz Hillman EyeWorld Senior Staff Writer 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 appropriate 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 degrees 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 opinions on management of a rotated toric IOL vary. Who’s at higher risk? A toric lens can rotate out of position, 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 preoperatively can often help guide intraoperative strategies to reduce that postoperatively,” Dr. Baartman 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 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.” Preventive measures The first step to optimal toric IOL performance is placing it on the correct 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 aberrometry, thinking that it’s not as accurate compared to preoperative measurements, among other reasons. He finds conducting preoperative measurements 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 capsular 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 extremely large eyes, unless there is a significant amount that can’t be easily corrected with an LRI. If I have a patient with a 29–30 mm eye and they’re with-the-rule and the Barrett formula is telling me to put in a low power toric, I tend to avoid that because I don’t think it’s worth the risk of rotation to correct a diopter of astigmatism, which I can correct with an LRI. If, on the other hand, a higher power toric Intraoperative photo of Symfony toric lens (Johnson & Johnson Vision) undergoing rotation by 16 degrees. Limbal marks are made with the 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 linking at the intended mark. Source: Brandon Baartman, MD