The eye displays considerable individuality in recovering from ocular procedures — especially following cataract surgery, as intraocular lenses (IOLs) settle in. In some cases, residual astigmatism with nontoric IOLs may also be a consideration. A trial suggests that a rotationally stable toric IOL can provide predictable visual outcomes without necessitating further strategies, such as eyeglasses, refractive laser “touch-up,” or a sulcus-fixated supplementary IOL. Results of the prospective study, conducted December 2014 to November 2017 are published in BMC Ophthalmology.

The trial reviewed the use of the Aktis NS60YT (Nidek), a 1-piece toric IOL with anchor-wing haptic design (ClinicalTrials.gov Identifier: NCT03242486). Findings show that, at 6 months postoperative, 90% of eyes in the trial achieved visual acuities with spherical addition of 0.1 logMAR or better. This indicates that patients can achieve equivalent or better postoperative VA with the NS60YT in comparison with commercially available toric IOLs.

The trial enrolled 64 eyes of 53 patients (mean age 68.6±9.5 years with ≥1.0 D of regular corneal astigmatism). Lens cylinder powers assessed were 1.50 D, 2.25 D, 3.00 D, and 4.50 D. “Twelve months after surgery, the outcomes of the current study indicate a sphere-corrected VA of less than 0.1 logMAR in only one eye (2%), and 0.1 logMAR or better in the other 60 eyes (98%),” the investigation explains, adding that results indicate “excellent cylinder correction.”


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Of total participant eyes, 59% achieved residual subjective cylindrical power of less than 0.50 D, and 89% obtained less than 1.00 D. Mean rotation change of the IOL between visits from 1 day to 12 months postoperative was 1.9° to 2.5°. Rotation averaged 5.0±4.4° at 6 months, and 5.3±4.3° at the trial’s conclusion. For 89% of eyes, insertion axis to final axis was less than 10°, and in 8% the lens did not show any rotation. 

Prior studies with other single-piece IOLs have found a typical 6-month rotation beyond the target axis of between 2° to 9°. The current analysis concurs with previous research examining one-piece toric IOLs in that if they rotate, it is relatively soon after surgery and then the lens stabilizes.

Rotational stability of the NS60YT is promoted by the 90° orientation of anchor-wing haptics, creating endurance to withstand compression from capsular contraction, as well as width between haptic shoulders calculated from average capsular diameter, according to the report. 

Four eyes experienced mild opacification of the posterior capsule, 2 eyes developed secondary cataract, and IOP was raised in 4 eyes. Overall, the lens is “safe and effective,” according to investigators. At the 6-month follow-up, 62 eyes of 52 patients completed all study protocols, and 61 eyes of 51 participants finished at 12 months. Participant satisfaction was surveyed at 6 months postoperative, with 52% very satisfied, 40% satisfied, 3% neither satisfied nor dissatisfied, 5% dissatisfied, and 0% very dissatisfied.

Visual acuity with spherical addition was the primary objective evaluated in this study, because many cataract patients in Japan opt for a degree of post-op myopia compared with emmetropia, the paper noted. Limitations of the trial include no assessment for the difference between intended IOL insertion axis and actual insertion axis, as well as only 5 eyes presenting with high astigmatism for testing the 4.50 D lens. Also, this study was based on a 2014 design using only the anterior corneal surface to determine astigmatism without encompassing posterior corneal curvature. 

Disclosure: The study was supported by Nidek Co., LTD. Several study authors disclosed affiliations with the biotech, pharmaceutical, and/or medical device industries. Please see the original reference for a full list of authors’ disclosures.

References

Sugita I, Ogawa T, Ichikawa K, et al. Rotational stability and clinical outcomes of a new one piece toric intraocular lens with anchor-wing haptics. BMC Ophthalmol. 2022;22(26):1–10. doi:10.1186/s12886-021-02240-7