This was a single-surgeon, retrospective study of patients undergoing femtosecond laser-assisted cataract surgery with arcuate incisions for the reduction of astigmatism. Arcuate incision anatomy was calculated using the LaserArcs online nomogram. The primary endpoint of this study was the percent reduction in absolute magnitude of astigmatism in the subject population based upon the absolute difference of postoperative manifest refraction. Postoperative manifest cylinder was the exploratory endpoint.
All patients had undergone a preoperative manifest refraction, and keratometry was determined using an IOLmaster V (Carl Zeiss Meditec, Oberkochen, Germany) with software version 5.2.1 to 5.4 or a LenStar LS900 (Haag-Streit, Bern, Switzerland) version 4.2.1 to 4.4.0, which are comparable instruments for the purposes of corneal power measurement.12 (link) Posterior corneal astigmatism and central topography were both included in these calculations. Biometry data was manually uploaded to the online LaserArcs software for calculation, and a graphical printout (Figure 1) was generated for use in surgery.

The LaserArcs software graphical output. Reprinted with permission from LaserArcs.

All arcuate incisions were made to an 8.0 mm diameter at a depth 80% of the corneal thickness as measured by the OCT corneal depth measurement of the LenSx (Alcon, Ft Worth) femtosecond laser. Laser arcuate incisions were not further manipulated or opened by the surgeon. The femtosecond laser was also used to create an anterior capsulotomy of 5.5 mm and for lens fragmentation. No other incisions were made with the femtosecond laser. No toric lens implants were used in study eyes, and an attempt was made to include about 30% of patients receiving multifocal implants with preoperative cylinder less than 0.7 D, so the study could evaluate the common scenario of correcting astigmatism with a multifocal implant where a sufficiently low toric power is not available. All postoperative refraction data was collected one month after surgery.
A sample size estimation was performed using results from an independent data set of 400 eyes and determined that 50 unilateral eyes would provide >90% statistical power to demonstrate a clinically meaningful percent reduction of astigmatism with a target reduction of 60%. All enrolled subjects were required to be 22 years of age or older and had cataracts but otherwise healthy eyes, not exhibiting any significant ocular morbidity that would be expected to influence outcome measures. All patients had preoperative keratometric astigmatism greater than 0.25 D and were implanted with a non-toric IOL, and all patients’ laser astigmatic keratotomy was planned using the LaserArcs nomogram. Patients with visually significant co-morbidities that could affect their visual outcome after surgery, like corneal, retinal, or optic nerve disease, were excluded, and all patients had a preoperative corneal topography screening for ectasia, higher-order aberrations, or other abnormalities and would be excluded from treatment if significant corneal pathology were identified. Patients with surgical complications either during or after surgery (capsule tears, iris trauma, decentered IOL, cystoid macular edema, etc.) that would, in the judgment of the investigator, influence the outcome measures of the study, and patients with previous refractive surgery prior to cataract surgery were also excluded.
Prior to collection of retrospective data, this study was registered on ClinicalTrials.gov as NCT 05278442. It was also approved by WCG IRB (Puyallup, Washington) as protocol 20220599 and adhered to both the Declaration of Helsinki and good clinical practices as defined by the U.S. Food and Drug Administration. A waiver of written informed consent was provided by the IRB. Reasonable requests for de-identified patient data relating to the study findings will be available through the corresponding author for 5 years following the publication date.