October 2018

RESIDENTS

YES connect
Toric IOL rotated—now what?


by Liz Hillman EyeWorld Senior Staff Writer

Toric intraocular lenses are a wonderful 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 placement including specialized instruments, intraoperative aberrometry, and even apps. Some surgeons will utilize high resolution photography to compare the axis to prominent vessels and other structures in the eye to serve as a guide.
For those of you in training, I recommend 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

“I think all patients getting
premium lens implants, including torics, should be made aware of the potential for residual astigmatism and possibility of a fine tune in the future, which could include a laser or IOL rotation.”
—Brandon Baartman, MD

How to manage toric IOL rotation postoperatively and preventative measures to take intraoperatively

The 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.”

Preventative 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 is called for, we are more likely to use it.”
In addition to considering placement of a CTR, Dr. Baartman noted several other intraoperative pearls to help reduce the risk of lens rotation. One is diligent removal of all viscoelastic from the capsular bag, including behind the lens. Another is nailing the capsulotomy to ensure 360 degrees of capsular overlap with the optic because it’s thought increased contact helps prevent lens tilt and rotation postop, Dr. Baartman said. Surgeons can also consider leaving the eye somewhat soft relative to the patient’s usual ocular tension at the end of the case, with the idea that it will allow proper collapse of the capsular bag around the lens, Dr. Baartman said.
“Lastly,” he added, “I think all patients getting premium lens implants, including torics, should be made aware of the potential for residual astigmatism and the possibility of a fine tune in the future, which could include a laser or IOL rotation. When you have these discussions with patients before surgery and you do encounter the scenario after surgery, it’s less of a surprise to the patient and makes it feel like less of a complication to both parties.”
Dr. Safran said using a cohesive viscoelastic in the injector may slightly reduce the risk of rotation postoperatively because it is less likely to coat the haptics and remain in place compared to a dispersive viscoelastic. He also recommended polishing lens epithelial cells from the capsular bag, thinking it makes the “capsular bag a little tackier” for the IOL to stay in position. “Some surgeons think that the increased fibrosis and capsule contraction caused by retained LECs prevents rotation, but these LEC-induced capsular bag changes do not occur for weeks, until long after the lens is likely rotate.”

Postoperative management

Careful postoperative refraction is critical in determining the possible need for a toric adjustment, Dr. Baartman said. He prefers to wait until the patient’s refraction is stable before going in to reposition the lens, though if the rotation is significant he might go in earlier.
“Generally, I like to be sure of the refractive stability and the patient’s lens position, that it’s not going to continue to move before going in for a second surgery. The caveat here is waiting too long puts the patient through a longer delayed optimal position and might make the procedure difficult if the bag seals down,” he said.
Dr. Baartman said he uses astigmatismfix.com, a program that helps identify the optimal toric lens position of a given toric IOL and the postoperative refraction.
“You get a magnitude of change required in the exact position compared to its current position to reduce the amount of astigmatism,” he explained.
If, after plugging numbers in, he finds residual astigmatism even after toric rotation would still be visually significant, Dr. Baartman said he considers IOL exchange or laser ablation.
“Sometimes when there is a pristine cornea and no irregular astigmatism noted on topography and we know that we are at a good position with the toric lens rotationally but our spherical power is off, we’re more likely to go in and change the lens power. Generally, if we’re within a diopter of spherical equivalent, we’ll do a laser, which is less risk for the patient than going in and exchanging the lens,” Dr. Baartman said.
When Dr. Baartman is going in to rotate a toric lens, he said he is more likely to rely on the axis proposed by astigmatismfix.com vs. intraoperative aberrometry, which he used when placing the lens primarily.
In terms of knowing when to correct a rotated toric, that depends on your threshold, Dr. Safran said.
“If you’re using a low power toric and it’s rotated 5 or 10 degrees, that might only be a 10th of a diopter,” he said. “If it’s a higher power toric, that could become a significant amount.”
Dr. Safran said he refracts his patients at postop day 1 and again at 1 week postop. If the toric lens is not where he wants it to be and it’s causing enough residual astigmatism to be considered significant, he will take a 30-gauge needle, go in through the limbus, and rotate it appropriately just at the slit lamp.
“Most doctors don’t do slit lamp rotation like I do; they’re not comfortable with it. So I tell those doctors if you have a rotated toric in a high myope, wait about 5–6 weeks to fix it so the capsular bag can contract a little. If you fix them right away, there’s a greater chance they’ll reoccur and you’re back to where you started. … If you place a CTR you also reduce the risk of the lens rotating again,” Dr. Safran said. “If you are going to rotate the lens and you do it before 5–6 weeks, you might want to put a CTR in because otherwise there is going to be a good chance of that lens rotating again.”
When rotating a patient at day 1 postop, Dr. Safran said he doesn’t use software, sticking with rotating them back to where the original operative plan had intended. If you wait 5–6 weeks before rotating, however, he recommended the Barrett Rx formula or astigmatismfix.com. He pointed out that fibrosis should be considered, even if rotation is occurring at the 1-month mark. Freeing up the haptics and recognizing the common points of adhesion that are specific to the IOL is important, he said, but noted that there won’t be any fibrosis if rotation occurs within 1–2 days postop.
Dr. Safran said he will always reposition off-axis lenses vs. correcting residual astigmatism with a laser, provided the patient has not had a YAG laser posterior capsulotomy. If he finds the wrong toric power altogether was used, he will exchange the lens.
“To me, to change the cornea to compensate for a rotated lens is not the right way to fix it because you’re compensating in a way that I don’t think is going to provide as good of a refractive outcome as to fix the problem directly,” he said.

Reference

1. Ma JJ, Tseng SS. Simple method for accurate alignment in toric phakic and aphakic intraocular lens implantation. J Cataract Refract Surg. 2008;34:1631–6.

Editors’ note: Dr. Safran and Baartman have no financial interests related to their comments.

Contact information

Baartman
: brandon.baartman@vancethompsonvision.com
Safran: safran12@comcast.net

Toric IOL rotated—now what? Toric IOL rotated—now what?
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