May 2018

CATARACT

Head-to-head comparison of toric IOLs shows one significantly more likely to rotate by postop day 1


by Liz Hillman EyeWorld Senior Staff Writer


Despite ensuring correct axis alignment, confirmed with a digital marking system, this study showed IOL rotation was possible within postop day 1. This image shows a Tecnis toric IOL with the Callisto overlay.
Source: David F. Chang, MD

Tecnis monofocal toric lens found to rotate more than AcrySof toric lens

Stable alignment of toric IOLs is critical for achieving a desired refractive outcome. Just 1 degree of misalignment results in about 3.5% loss of cylindrical correction, 2 degrees up to about 7%, and 10 degrees more than 34%.1
Even if the surgeon aligned the IOL on the proper axis, postoperative rotation can and does occur, impacting refractive results. In a study published in Ophthalmology, David F. Chang, MD, clinical professor of ophthalmology, University of California, San Francisco, and Altos Eye Physicians, Los Altos, California, and Bryan S. Lee, MD, JD, in private practice with Dr. Chang at Altos Eye Physicians, Los Altos, sought to compare the postoperative rotational stability of the two most commonly implanted toric monofocal IOLs.2
“Toric IOLs are the most common premium IOL in our practice,” Dr. Lee said. “We integrated intraoperative aberrometry, then a digital marking system to increase the accuracy of our toric IOL placement, so it was natural for us to study the next step—whether the IOL stays where we put it.”
Dr. Lee and Dr. Chang compared the axis alignment of the Tecnis toric monofocal IOL (Johnson & Johnson Vision, Santa Ana, California) and the AcrySof toric monofocal (Alcon, Fort Worth, Texas) at the first postoperative visit (either day 0 or day 1). The lenses were implanted at a single ambulatory surgery center by the two surgeons using intraoperative wavefront aberrometry (ORA VerifEye+, Alcon) and the Callisto Eye digital marking system (Carl Zeiss Meditec, Jena, Germany). Dr. Chang said he and Dr. Lee were not aware of any head-to-head studies evaluating postoperative rotational stability—an important factor in overall toric IOL performance—between these two platforms.
Six hundred and forty-seven Tecnis lenses and 626 AcrySof lenses were implanted during the 18-month study period. Overall, the AcrySof lens showed statistically better rotational stability when compared to the Tecnis lens. More specifically, the AcrySof lens rotated <5 degrees in 91.9% of eyes, compared to 81.8% with the Tecnis lens (P<0.0001), and <10 degrees in 97.8% of eyes compared to 93.2% with the Tecnis (P=0.0002). The net mean rotation of the AcrySof lens was 2.72 degrees, compared to 3.79 degrees with the Tecnis (P<0.05). Though it did not quite reach statistical significance (P=0.1), more patients with the Tecnis lens underwent IOL repositioning compared to the AcrySof (3.1% v. 1.6%).
Though Tecnis lenses were more likely to rotate by the first postop visit, the net mean refractive outcomes between the two groups were similar.
“Although the groups were similar demographically, the AcrySof group had significantly higher preoperative astigmatism,” Dr. Lee explained. “Furthermore, about half of the patients in each group had the lowest power toric IOL, which corrects 1 D of cylinder at the corneal plane. In those eyes, the refractive effect of a rotated IOL would be more limited. These factors might have canceled out the fact that the AcrySof toric is 10% less likely to rotate more than 5 degrees.
“The problem was not the mean difference in IOL stability, which was statistically significant but small (1 degree in favor of AcrySof),” Dr. Lee continued. “It was the number of large rotations in the Tecnis group—these are the patients who are unhappy because of their poor refractive outcomes.”
“Overall, we would conclude that both toric IOL models provide excellent refractive outcomes and good rotational stability. However, the large size of our study made it apparent that the AcrySof had superior rotational stability,” Dr. Chang added.
This is the largest study to date that directly compares rotational stability of these two toric IOLs. What’s more, Dr. Lee said it was important to look at rotational stability at the first postoperative visit.
“The FDA studies for toric IOL approval looked at stability after the first postoperative visit. However, we thought, based on clinical experience, that rotations happen before that,” Dr. Lee said. “The 2017 report by Inoue et al. that we reference eventually confirmed that, as they showed that 85% of their rotation happened in the first hour after surgery.”3 Dr. Chang added that 28% of the net mean toric IOL misalignment measured at 1 year in the Inoue study, where patients were manually marked preoperatively, was due to surgical misalignment. “This means prior studies of toric IOL misalignment using manual marking were unable to differentiate between surgical misalignment and postop IOL rotation,” he said. “By using intraoperative digital alignment with Callisto in all eyes, we were able to isolate postoperative IOL rotation as a variable when comparing the two different toric IOLs.”
Dr. Chang observes intraoperatively that there is more stiffness to the Tecnis IOL haptic and its optic-haptic junction, which he thinks could increase the likelihood of it rotating when compressive forces are applied to it.
“The reduced compression force of the AcrySof toric haptic, which is more floppy, probably allows it to absorb any pressure applied to the IOL by more readily flexing,” Dr. Chang said. “Imagine equatorial point pressure applied to the haptic midway between its tip and the optic junction. If it were limp, like a noodle, the haptic would simply flex. If it were stiffer and rigid, the force would be transmitted to the entire lens, and it might tend to turn counterclockwise as the pressure follows the natural curve of the haptic.”
Why do IOLs seem to rotate so early in the postop period? Dr. Lee speculated that the haptics might be continuing to expand in some cases, or perhaps leakage of the wound or retained viscoelastic around the haptics could be a factor.
“It takes awhile for the capsular bag to shrink and collapse around the IOL,” Dr. Chang said. “Anecdotally, I think it helps to leave the eye slightly hypotonous at the conclusion of surgery. Inflating the eye with balanced salt solution tends to simultaneously expand the capsular bag.”
As a result of this study’s findings, Dr. Lee said he prefers to use the AcrySof as his usual monofocal toric IOL. Though toric IOL repositioning is straightforward, he said the associated inconvenience, expensive of a return to the OR, and the theoretic risk for infection or zonular damage have him trying to avoid the need altogether. The IOLs that they did have to rotate in the study period, however, were stable afterward, Dr. Lee noted.
“I think the take-home message is that if you have an IOL rotation, wait a couple of weeks, then fix it because your patient will be much better off,” Dr. Lee said.
Dr. Chang said he prefers the AcrySof as a monofocal toric option, but he also implants many Symfony and Symfony toric IOLs. If the first eye develops 10 degrees or more of misalignment, he’ll reposition it simultaneously with cataract surgery in the second eye. He’ll then use a capsular tension ring (CTR) with the Symfony toric in the second eye. He said he might also use a CTR if the patient has high axial myopia or conditions that would make repositioning difficult, such as a small pupil, or if the patient is from out of town.
“I think that a CTR reduces rotation, but we didn’t directly study or prove this,” Dr. Chang said.
The Inoue et al. study also mentioned limiting patient activity in the immediate postop period as a possible way to prevent IOL rotation.
“I routinely tell all patients immediately upon conclusion of their surgery to keep their eye relaxed and avoid squeezing as I remove the speculum and drape,” Dr. Lee said. “We use a powered reclining chair in our surgery center, and I tell patients not to make any effort to sit up after the surgery and let the chair do all the work. I also tell them to be extremely careful to avoid eye rubbing, lifting, and straining and to move in ‘slow motion’ for the first 24 hours.”
Dr. Chang also said he will tell patients to avoid exercise and limit walking immediately following their surgery.
“I imagine that once the patient leaves the ASC and starts walking, that may be just enough activity to allow some toric IOLs to move,” Dr. Chang said, acknowledging that he has “no idea” if limiting activity during the immediate postop period actually helps prevent rotation.
Dr. Chang said he and Dr. Lee have shared their findings with Johnson & Johnson Vision, which is evaluating haptic modifications that could improve rotational stability of the Tecnis toric IOL. He said when adjustable IOLs become available, they will be the best toric platform.
“[The] lack of potential rotation following adjustment will be one of the reasons why,” Dr. Chang said.

References

1. Ma JJ, et al. Simple method for accurate alignment in toric phakic and aphakic intraocular lens implantation. J Cataract Refract Surg. 2008;34:1631–6.
2. Lee BS, et al. Comparison of the rotational stability of two toric intraocular lenses in 1273 consecutive eyes. Ophthalmology. 2018 Mar 12. Epub ahead of print.
3. Inoue Y, et al. Axis misalignment of toric intraocular lens: placement error and postoperative rotation. Ophthalmology. 2017;124:1424–1425.

Editors’ note: Dr. Chang has financial interests with Carl Zeiss Meditec, Johnson & Johnson Vision, and RxSight (Aliso Viejo, California). Dr. Lee has no financial interests related to his comments.

Contact information

Chang
: dceye@earthlink.net
Lee: bryan@bryanlee.pro

Head-to-head comparison of toric IOLs shows one significantly more likely to rotate by postop day 1 Head-to-head comparison of toric IOLs shows one significantly more likely to rotate by postop day 1
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