Toric intraocular lens versus arcuate keratotomy: femtosecond laser enters the debate

Zhong et al. address the problem of treating corneal astigmatism and particularly the issue of treating lower levels of corneal astigmatism at the time of cataract surgery (1). While cataract extraction and implantation of a toric intraocular lens (IOL) provide effective treatment for higher levels of corneal astigmatism (2), treating mild corneal astigmatism is more challenging. Alternative techniques to treat mild corneal astigmatism at the time of cataract surgery include light-adjustable IOLs, small-aperture lenses, incisions in the plane of the steep corneal axis, paired incisions, arcuate relaxing incisions (3) and in the case of this article, femtosecond laser arcuate keratotomy.

Prior analysis shows an advantage for toric IOLs compared to manual corneal incisions in the correction of astigmatism (2). However, manual corneal incisions may not be as precise and reproducible as corneal incisions created by a femtosecond laser. As Zhong et al. note in their paper, most studies comparing standard cataract surgery with toric IOL implantation to femtosecond laser-assisted cataract surgery with arcuate keratotomy have shown similar refractive outcomes. In these studies, however, the capsulotomy was created manually for the cases with toric IOL implantation. Therefore, it was unknown how refractive outcomes compare between femtosecond laser-assisted cataract surgery with arcuate keratotomy and femtosecond laser-assisted cataract surgery with toric IOL implantation.

To address this knowledge gap, Zhong et al. evaluated refractive results after femtosecond laser-assisted cataract surgery with either implantation of a toric IOL or femtosecond laser arcuate keratotomy in eyes with regular corneal astigmatism ranging from 0.75 to 3.0 diopters preoperatively (1). In this randomized controlled trial conducted over a two-year period, the authors did not detect a significant difference between groups for the primary study outcome, magnitude of refractive astigmatism at the three-month postoperative evaluation (P=0.21). The study also showed comparable results for uncorrected distance visual acuity (UDVA), a key secondary outcome: mean ± standard deviation UDVA was 0.15±0.20 logMAR in the laser arcuate keratotomy group and 0.14±0.19 logMAR in the toric IOL group (P=0.71). The Snellen equivalent mean UDVA was 20/28 in both groups, consistent with a good refractive outcome.

A retrospective study investigating the same methods for correcting mild corneal astigmatism at the time of cataract surgery also showed non-inferiority between femtosecond laser-assisted cataract surgery with arcuate keratotomy and femtosecond laser-assisted cataract surgery with implantation of a toric IOL (4). Although this was not a randomized controlled trial, it was a relatively large study, with 52 eyes in the arcuate keratotomy group and 53 eyes in the toric IOL group. One key difference between the two studies is the magnitude of preoperative corneal astigmatism, which ranged from 0.75 to 3.0 diopters in Zhong et al.’s study (1) compared to 0.6 to 1.1 diopters in the retrospective study (4). Taken together, these two studies show that femtosecond laser-assisted cataract surgery with arcuate keratotomy and femtosecond laser-assisted cataract surgery with toric IOL implantation have comparable efficacy in correcting low levels of regular corneal astigmatism.

Some differences between groups, all favoring the toric IOL group, did emerge in post hoc subgroup analyses that differentiated eyes based on the magnitude and direction of preoperative corneal astigmatism in Zhong et al.’s study (1). There was significantly more refractive astigmatism at the three-month postoperative assessment in the laser arcuate keratotomy group than in the toric IOL group in the subgroup of eyes with corneal astigmatism ranging from 1.5 to 3.0 diopters preoperatively (P=0.009) and in the subgroup of eyes with preoperative against the rule corneal astigmatism (P=0.04). There were also fewer eyes with ≥0.75 D of astigmatism at the 3-month postoperative assessment in the toric IOL group than in the laser arcuate keratotomy group. However, these are post hoc analyses, so additional studies are indicated to more conclusively evaluate whether femtosecond laser-assisted cataract surgery with toric IOL implantation is superior to femtosecond laser-assisted cataract surgery with arcuate keratotomy in eyes with moderate corneal astigmatism, in eyes with against the rule corneal astigmatism, and in prevention of large refractive errors after surgery.

One limitation in Zhong et al.’s study is the lack of patient-reported outcome measures in the study design. Investigators evaluating the efficacy of other refractive procedures have begun to incorporate patient-reported outcome measures into their studies (5). Future studies incorporating patient-reported outcome measures and directly assessing spectacle independence would be beneficial in assessing outcomes important to patients undergoing refractive surgery.

Lastly, what remains to be seen is the long-term efficacy of treating lower levels of astigmatism. Although findings from a recent meta-analysis indicate that femtosecond laser arcuate keratotomy continues to provide effective astigmatism correction up to a year after surgery (6), analysis of long-term outcomes is limited. Refractive outcome analysis for toric IOLs shows that while the rotational position of toric IOLs tends to remain stable after the 1-month postoperative period (7), astigmatic changes still may occur after the early postoperative period (8). As the eye ages, biomechanical corneal changes tend toward against-the-rule astigmatism (9). Although the constantly changing techniques of measuring and treating corneal astigmatism may be a limiting factor, further study to evaluate the long-term efficacy of lower levels of astigmatism correction would be informative for patients and surgeons.

Acknowledgments

This work solely represents the views of the authors and does not represent the view of the U.S. Department of Veterans Affairs or the United States Government.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Eye Science. The article did not undergo external peer review.

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://aes.amegroups.com/article/view/10.21037/aes-2026-1-0004/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

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