This multicentre, single-arm clinical trial was approved by the Investigational Review Boards of Osaka Clinical Trial Hospital (For Chukyo Eye Clinic, Fujita Eye Clinic, and Roppongi Shiba Eye Clinic [Japan]) and Miyata Eyes Hospital (Japan). Written informed consent was obtained from each patient. The study adhered to the tenets of the Declaration of Helsinki and the ‘Ministerial Ordinance on Good Clinical Practice for Medical Devices’ (Ordinance of the Ministry of Health, Labour and Welfare No. 36, 2005). This study was registered at ClinicalTrials.gov (ID: NCT05255029).

This study was designed to assess the outcomes of the PODEYE TORIC IOL (POD T 49P) in groups categorised according to cylinder power: eyes with toric IOLs of cylinder powers of 1.50 D to 6.00 D and 1.00 D cylinders, respectively. Toric IOLs were implanted in the capsules of patients 20 years or older with cataracts from the Japanese population after cataract-removal utilising phacoemulsification and aspiration procedures. The exclusion criteria included ocular pathology influencing postoperative vision, except for cataracts, a history of previous ocular surgery, corneal abnormalities, previous corneal transplant, poor mydriasis, glaucoma, amblyopia, optic nerve atrophy or intraoperative complications.

Primary endpoints of the study included non-inferiority in uncorrected distance visual acuity (UDVA) in the use of PODEYE TORIC with a cylinder power of 1.50 to 6.00 D at 6 months postoperatively and superiority in refractive cylinder values in the use of the 1.00 D cylinder power model. The sample size for each endpoint was calculated as follows: 1) The mean UDVA was estimated as 0.07 logMAR with a 95% confidence interval (CI) of 0.054–0.086 logMAR according to our in-house data. To examine the non-inferiority of UDVA to AcrySof IQ toric IOLs (Alcon) with a standard deviation (SD) of 0.15 [13], 24 eyes or more were required under a margin of 0.10, one-sided significance level of 2.5%, and a power of 90%. Considering a 10% drop-out rate, the required sample size was 29. 2) Similarly, the SD of the refractive cylinder was estimated to be 0.5 D based on our in-house data and previous results [5]. To examine superiority to eyes with non-toric IOL, SN60WF IOL (Alcon) [5] was used with a difference of 0.3 D and SD of 0.5 D, a significance level of 2.5% (one-sided), and a power of 80%. A total of 24 eyes was required. Considering a 10% drop-out, the required sample size was 27. Then, based on sample size calculations, the total sample size was 56.

The implanted toric IOLs were the PODEYE TORIC model, and the material was a cross-linked, acrylate/methacrylate copolymer with a blue light absorber (refractive index of 1.53), with a biconvex, aspheric, optic diameter of 6.0 mm and an overall length of 11.4 mm. The IOL possessed haptics of a double C-loop design (Fig. 1), which symmetrically sustained the IOL with four haptics to ensure stability in the capsule. As toric IOLs, seven models with cylinder powers of 1.00, 1.50, 2.25, 3.00, 3.75, 4.50, 5.25, and 6.00D added to the posterior optics were available. The unique haptics consist of four C-loops for better centralisation.

PODEYE TORIC (POD T 49P) intraocular lens with double C-loop haptics (picture property of BVI)

Corneal astigmatism and axial length were measured preoperatively using keratometry and biometry, respectively. Biometry included swept-source optical coherence biometers; IOL Master 700 (Carl Zeiss Meditec AG) in 2 sites, ARGOS (Alcon) in a site, and OA-2000 (Tomey) in one site. Powers of IOLs were determined for emmetropia using the Barrett Universal II formula with the lens constant of 2.15. The toric model and axis position were determined using the Toric Calculator (available at http://www.physioltoric.eu), which is based on the Abulafia–Koch regression formula [14]. Surgically-induced astigmatism at each site was used. After cataract removal through incisions of 2.2 to 3.2 mm, the IOL was implanted in the capsule using a specific injector (Accuject, Medicel AG). The toric IOL axis was aligned at the calculated position using the surgical guidance system at each site. All the participants received standard regimens of preoperative, operative, and postoperative medication.

UDVA, corrected distance visual acuity (CDVA), and manifest refraction (sphere and cylinder) were recorded at 6 months postoperatively. UDVA and CDVA were measured using Landolt ring charts at a 5-m distance under photopic illumination (85–110 cd/m2) and converted to logMAR notation for analysis. During CDVA examinations, manifest refractions were recorded, and spherical equivalent (SE) values were calculated.

As misalignment of the toric IOL from the calculated position resulted in the degradation of the astigmatic correction, the IOL axis mark positions were measured 1 day and 3 months after surgery. After mydriasis, an anterior segment image of the implanted IOL was captured and the axis mark position was measured using Photoshop (Adobe).

The primary endpoints were non-inferiority in the UDVA and superiority in the refractive cylinder at 6 months postoperatively. 1) The non-inferiority in UDVA was examined using a toric IOL with a cylinder power of 1.50 to 6.00 D. Because bilateral implantations were included, mixed-effect models for repeated measures (MMRM) were used to calculate the least-squared mean and 95% CI at 6 months postoperatively. The non-inferiority of the AcrySof IQ toric IOL was examined if there was an upper limit of 95% CI <0.2 logMAR (estimated mean of 0.1 logMAR [13] and a margin of 0.1 logMAR). 2) The superiority of the refractive astigmatism in the use of a 1.00 D-cylinder toric IOL over a non-toric IOL was explored. Using MMRM, the least-squared mean and 95% CI of the refractive astigmatism were calculated. The superiority in which the upper limit of 95% CI should be <0.8 D (mean + SD) was examined. The absolute difference between the measured axis mark positions at different times post-surgery was calculated as the IOL rotation, and a median and ratio of <10° were obtained. P<0.025 and P <0.05 were considered as statistically significant for one-sided and two-sided analyses, respectively.