Low-cylinder-power toric IOLs effectively reduced residual astigmatism and improved uncorrected vision in eyes with mild astigmatism, demonstrating their clinical value and extending candidacy beyond conventional toric ranges.
Abstract
Purpose:
To evaluate the effectiveness of astigmatism correction using low-cylinder-power monofocal toric intraocular lenses (IOLs) in eyes with mild corneal astigmatism.
Setting:
Tertiary care center in Osaka, Japan.
Design:
Single-center ambispective observational cohort study.
Methods:
Eyes were categorized into the T2 group (toric IOL with 1.0 diopter [D] cylinder power at the IOL plane), nontoric IOL (T0) group, or Tx group (T3 or higher toric IOLs; ≥1.5 D cylinder power). Eyes with irregular corneal astigmatism or prior ocular surgery were excluded. 3-month outcomes included uncorrected distance visual acuity (UDVA), refractive and subjective astigmatism, and vector analysis.
Results:
75 eyes (25 per group, 46 patients) were analyzed. At 3 months, the T2 group showed significantly lower mean refractive astigmatism (0.45 ± 0.25 D) and subjective astigmatism (0.28 ± 0.34 D) than the T0 group (0.92 ± 0.31 D and 0.69 ± 0.33 D; both P = .000), with better UDVA (logMAR −0.05 ± 0.12 vs 0.08 ± 0.15; P = .002). In paired-eye analyses, T0 eyes had greater refractive astigmatism (0.92 ± 0.32 D) and subjective astigmatism (0.69 ± 0.33 D) than their Tx fellow eyes (0.53 ± 0.33 D; P < .001 and 0.39 ± 0.32 D; P = .002). T2 achieved astigmatism correction comparable with that of Tx in mild-astigmatism eyes. Tx eyes trended toward better UDVA than their T0 fellows (P = .060).
Conclusions:
Low-cylinder-power toric IOLs effectively corrected astigmatism and improved visual outcomes in eyes with mild corneal astigmatism, a population previously excluded from toric IOL implantation.
Toric intraocular lenses (IOLs) reduce residual postoperative astigmatism and improve uncorrected visual function by correcting corneal astigmatism with a cylindrical power incorporated into the optic.1 Toric IOLs were first introduced in Japan in 2011 with the monofocal AcrySof IQ Toric IOL (SN6AT, Alcon Laboratories, Inc.), which was initially available only in cylinder powers T3 through T9, without a T2 option (Table 1). This limitation reflects the prevailing view that toric IOLs are primarily intended for correcting moderate corneal astigmatism (1.5 to 2.0 diopters [D]) and high corneal astigmatism (>2.0 D).2–4 Notably, T2 toric IOLs remain unavailable in the United States.
Table 1.
Cylinder power of each toric IOL model at the IOL plane and the corneal plane
| Model | Cylinder power (D) at the IOL plane | Cylinder power (D) at the corneal planea |
| T2 | 1.00 | ≈0.65 |
| T3 | 1.50 | ≈0.98 |
| T4 | 2.25 | ≈1.47 |
| T5 | 3.00 | ≈1.96 |
| T6 | 3.75 | ≈2.45 |
| T7 | 4.50 | ≈2.94 |
| T8 | 5.25 | ≈3.43 |
| T9 | 6.00 | ≈3.92 |
The cylinder power at the corneal plane differs according to the IOL calculation formula applied
Most patients with cataract present with relatively low levels of corneal astigmatism, most commonly between 0.5 D and 1.5 D.5,6 In Japan, T2 toric IOLs became commercially available in April 2023 for presbyopia-correcting IOLs and in June 2024 for monofocal IOLs. Concurrently, both the manufacturer's web-based toric calculator and biometric devices such as the IOLMaster 700 (Carl Zeiss Meditec AG) were updated to include T2 in their toric calculation algorithms.7 These upgrades enabled candidacy determination, alignment axis, and predicted residual astigmatism for toric IOLs, which now include the T2 model.
Despite this recent introduction, to date, the real-world clinical effectiveness of T2 toric IOLs in correcting low corneal astigmatism has not been systematically evaluated. A subset of patients previously categorized as candidates for nontoric IOLs (T0) by earlier calculators are now deemed eligible for T2 by the updated Barrett toric calculator. Although some clinicians consider low-level astigmatism clinically tolerable without correction, others argue that even minimal uncorrected astigmatism can degrade postoperative visual quality.8 Moreover, measuring low astigmatism accurately is challenging, raising concerns regarding reproducibility and potential errors in toric planning.9 These uncertainties underscore the need to systematically evaluate the clinical performance of T2 toric IOLs in routine practice.
We investigated the impact of introducing T2 toric IOLs by (1) comparing outcomes of T2 vs T0 in eyes retrospectively determined to be T2-eligible, (2) performing paired-eye analyses of T0 vs ≥T3 toric IOLs (Tx) to assess tolerance of uncorrected low astigmatism within the same patients, and (3) evaluating astigmatism correction of T2 vs Tx using a vector analysis.
In this study, the Alcon Clareon T2 model, representing a low-cylinder-power toric monofocal IOL (1.0 D cylinder at the IOL plane), was evaluated. For clarification, the term “mild corneal astigmatism” in the title and Abstract corresponds to what is referred to as “low corneal astigmatism” in the main text; for consistency, the term “low” is used throughout the article.
METHODS
Ethics Approval
This study was conducted in accordance with the tenets of the Declaration of Helsinki and approved by the Institutional Review Board of our institution (approval no. 2024022802, approved on February 28, 2024) (Yukioka Hospital, Osaka, Japan). As this was a single-center ambispective observational cohort study without a prospective interventional component, trial registration was not required according to the institutional and national guidelines. The protocol was reviewed and approved by the institution ethics committee.
Patient Consent Statement
Written informed consent was obtained from all the participants before surgery.
Patients
This study included patients who underwent small-incision phacoemulsification with implantation of a monofocal IOL (Clareon Monofocal IOL, CNW0T0, 2, 3, 4, 5, 6, Alcon Laboratories, Inc.) performed by a single surgeon. The model code's final digit denotes the toric model: “0” indicates a nontoric (T0), whereas “2” and higher indicate toric IOLs.
The T2 group comprised 25 eyes from 21 consecutive patients (10 men [12 eyes], 11 women [13 eyes]; mean age 76.3 ± 5.6 years) who underwent T2 implantation between June 2024 and May 2025. Astigmatism types were classified as against-the-rule (61 to 120 degrees; 19 eyes), with-the-rule (0 to 30 degrees or 151 to 180 degrees; 0 eyes), or oblique (all other axes; 6 eyes).
The T0 group comprised 25 eyes that had received a nontoric IOL (T0) before the introduction of T2, although according to retrospective recalculation with the updated Barrett toric calculator (see the Toric Calculator subsection), they would have been recommended for T2 implantation.
To minimize potential temporal bias, surgical technique, surgical devices, and measurement protocols were identical between the T0 and T2 groups.
The Tx group consisted of the fellow eyes of the T0 group in which ≥T3 toric IOLs had been implanted (23 against-the-rule, 2 oblique).
Eyes with clinically significant corneal disease, irregular astigmatism, moderate-to-severe glaucoma, retinal disease, prior ocular trauma, or previous intraocular surgery were excluded to avoid confounding visual and refractive outcomes.
Keratometry and Axial Length Measurement
Preoperative keratometric values were obtained using the IOLMaster 700 (Carl Zeiss Meditec AG). Postoperative keratometry was measured with an autorefractor-keratometer (TONOREF III, Nidek Co., Ltd.). Irregular astigmatism was excluded using wavefront aberrometry (KR-1W, Topcon Medical Japan Co., Ltd.) and anterior segment OCT (CASIA2, Tomey Corp.). Axial length was measured using the IOLMaster 700. IOL power was calculated with the Barrett Universal II formula targeting emmetropia. A corneal refractive index of 1.3375 was applied, with IOL constants LF = 1.94 and DF = 5.0.
Toric Calculator
Toric planning, including model selection, was performed with the Barrett toric calculator embedded in the IOLMaster 700, integrated with the intraoperative guidance system.
Change in corneal astigmatism (SIACornea, as defined by Abulafia et al.) was set at 0.11 D (centroid value) based on prior institutional outcomes.10 Toric IOL model selection followed the calculator's recommendations: For against-the-rule astigmatism, model minimized residual astigmatism even if axis flipping occurred; for with-the-rule and oblique astigmatism, no flipping was applied. The T0 group was retrospectively determined to be T2-eligible using the updated calculator algorithm.
Surgical Technique
All procedures were performed through a 2.4 mm transconjunctival single-plane sclerocorneal incision.11 Reference images and keratometric data from the IOLMaster 700 were transmitted through institutional local area network to the operating microscope (Lumera 700 with RESCAN 700 OCT, Carl Zeiss Meditec AG). The intraoperative guidance system (CALLISTO eye, Carl Zeiss Meditec AG) was used to identify the incision site (0 degree for the left eye, 180 degrees for the right eye), IOL center, and toric alignment axis. All IOLs were implanted within the capsular bag, and intraoperative complications did not occur.
Postoperative Evaluation
Patients were followed up for 3 months postoperatively. Although the data collection period naturally differed between the T0 and T2 eras, surgical technique and measurement protocols were identical across groups. Postoperative refraction was measured using the autorefractor-keratometer described above.
Comparative Outcome Analyses Across T0, T2, and Tx Groups
Comparison of T2 vs T0
Outcomes were compared between the T2 group, in which eligibility was prospectively determined using the updated calculator, and the T0 group, in which cases were retrospectively identified as T2-eligible. Postoperative uncorrected distance visual acuity (UDVA), spherical equivalent, refractive astigmatism, and subjective astigmatism were analyzed.
Paired-Eye Evaluation of T0 vs Tx
For patients who received T0 in 1 eye and ≥T3 toric IOL in the fellow eye, postoperative UDVA, spherical equivalent, refractive astigmatism, and subjective astigmatism were compared within the same patient to evaluate the tolerance of uncorrected low astigmatism.
Astigmatism Correction With T2 vs Tx
Astigmatism correction with T2 was compared with that of ≥T3 toric IOLs using the Astigmatism Double-Angle Plot Tool (ASCRS).12 Preoperative corneal astigmatism and postoperative refractive astigmatism were converted to the corneal plane and analyzed for cumulative distribution, mean absolute values, and centroids.
Statistical Analyses
The sample size calculations indicated that at least 23 eyes per group were required to detect a ≥0.25 D difference in postoperative refractive astigmatism, assuming a standard deviation of 0.30 D, 95% confidence, and 80% power. Accordingly, 25 eyes were included per group. Left-eye data were mirrored to account for enantiomorphism.
Statistical analyses were performed with JMP v. 17.10 (SAS Institute, Inc.). Paired t tests were applied for within-participant comparisons between T0 and Tx, whereas the Welch 2-sample t test and Fisher exact test were used for comparisons between T2 and T0. A P value less than 0.05 was considered statistically significant. Some outcomes, such as percentage distributions of astigmatism reduction, are presented descriptively without formal statistical testing.
RESULTS
Overall, 75 eyes from 46 patients were analyzed. The T2 group included 25 eyes (33%) from 21 consecutive patients, T0 group comprised 25 eyes (33%), and Tx group consisted of the 25 fellow eyes (33%) to those in the T0 group.
Safety and Overall Outcomes
No intraoperative or postoperative complications were encountered, including clinically significant axis misalignment or patient dissatisfaction. All eyes achieved a postoperative corrected distance visual acuity of 20/30 or better.
Baseline Characteristics
Tables 2 and 3 summarize baseline demographic and ocular characteristics.
Table 2.
Baseline characteristics: T2 group vs T0 group
| Parameter | Total (n = 50) | T2 group (n = 25) | T0 group (n = 25) | P valuea |
| Age (y) | 75.8 ± 7.7 (51.0, 90.0) | 76.3 ± 5.6 (67.0, 88.0) | 75.3 ± 9.4 (51.0, 90.0) | .638 |
| Sex | .140 | |||
| Women | 32 (64) | 13 (52) | 19 (76) | |
| Men | 18 (36) | 12 (48) | 6 (24) | |
| Axial length (mm) | 24.04 ± 0.99 (21.47, 26.39) | 24.25 ± 1.09 (21.47, 26.39) | 23.83 ± 0.85 (22.58, 26.17) | .139 |
| IOL power (D) | 19.8 ± 3.0 (11.5, 27.5) | 19.3 ± 3.4 (11.5, 27.5) | 20.4 ± 2.5 (14.5, 24.5) | .203 |
| Preop corneal astigmatism (D) | 0.471 ± 0.169 (0.163, 0.941) | 0.460 ± 0.185 (0.163, 0.941) | 0.483 ± 0.156 (0.217, 0.802) | .627 |
| Postop corneal astigmatism (D) | 0.559 ± 0.366 (0.000, 1.860) | 0.507 ± 0.319 (0.000, 1.340) | 0.610 ± 0.407 (0.060, 1.860) | .324 |
Data are mean ± SD (min, max); n (%)
Welch 2-sample t test and Fisher exact test
Table 3.
Baseline characteristics: T0 group vs Tx group
| Parameter | Total (n = 50) | T0 group (n = 25) | Tx group (n = 25) | P valuea |
| Model of toric IOL | — | |||
| T0 | 25 (50) | 25 (100) | 0 (0) | |
| T3 | 13 (26) | 0 (0) | 13 (52) | |
| T4 | 6 (12) | 0 (0) | 6 (24) | |
| T5 | 5 (10) | 0 (0) | 5 (20) | |
| T6 | 1 (2.0) | 0 (0) | 1 (4.0) | |
| Laterality | — | |||
| Right | 25 (50) | 9 (36) | 16 (64) | |
| Left | 25 (50) | 16 (64) | 9 (36) | |
| Axial length (mm) | 23.79 ± 0.85 (22.31, 26.17) | 23.83 ± 0.85 (22.58, 26.17) | 23.75 ± 0.87 (22.31, 25.92) | .178 |
| IOL spherical power (D) | 20.5 ± 2.4 (14.5, 24.5) | 20.4 ± 2.5 (14.5, 24.5) | 20.5 ± 2.4 (14.5, 24.5) | .425 |
| Preoperative corneal astigmatism (D) | 0.899 ± 0.561 (0.217, 2.465) | 0.483 ± 0.156 (0.217, 0.802) | 1.314 ± 0.509 (0.330, 2.465) | <.001 |
| Postoperative corneal astigmatism (D) | 0.878 ± 0.512 (0.060, 2.150) | 0.610 ± 0.407 (0.060, 1.860) | 1.145 ± 0.470 (0.320, 2.150) | <.001 |
Data are mean ± SD (min, max); n (%)
Paired t test
In the comparison between the T2 and T0 groups, no significant differences were observed in mean age (76.3 ± 5.6 years vs 75.3 ± 9.4 years; P = .638), sex distribution (52% vs 76% women; P = .140), axial length (24.25 ± 1.09 mm vs 23.83 ± 0.85 mm; P = .139), IOL power (19.3 ± 3.4 D vs 20.4 ± 2.5 D; P = .203), or preoperative corneal astigmatism (0.46 ± 0.19 D vs 0.48 ± 0.16 D; P = .627) (Table 2).
In the paired-eye comparison of T0 vs Tx, mean axial length (23.83 ± 0.85 mm vs 23.75 ± 0.87 mm; P = .178) and IOL power (20.4 ± 2.5 D vs 20.5 ± 2.4 D; P = .425) were not significantly different (Table 3). By definition, all T0 eyes had received nontoric IOLs, whereas Tx eyes had received T3 (52%), T4 (24%), T5 (20%), or T6 (4%). The mean preoperative corneal astigmatism was significantly greater in the Tx group compared with the T0 group (1.31 ± 0.51 D vs 0.48 ± 0.16 D; P < .001).
These findings indicate that the study groups were generally comparable in demographic and biometric parameters except for corneal astigmatism, which was higher in the Tx group due to design.
Comparison of T2 vs T0
At 3 months, postoperative refractive astigmatism was significantly lower in the T2 group (0.45 ± 0.25 D) than in the T0 group (0.92 ± 0.31 D; P = .000). Subjective astigmatism was likewise lower in the T2 group (0.28 ± 0.34 D) than in the T0 group (0.69 ± 0.33 D; P = .000). UDVA (logMAR) was significantly better in the T2 group (−0.05 ± 0.12) than in the T0 group (0.08 ± 0.15; P = .002) (Table 4).
Table 4.
Comparative outcomes: T2 group vs T0 group
| Variables | T2 group mean | T0 group mean | Difference of means | Standard deviation | 95% CI lower limit | 95% CI upper limit | T value | P value |
| Postop UDVA (logMAR) | −0.05 | 0.08 | −0.13 | 0.04 | −0.20 | −0.05 | −3.23 | .002 |
| Postop spherical equivalent (D) | 0.03 | 0.05 | −0.02 | 0.09 | −0.20 | 0.16 | −0.22 | .825 |
| Preop corneal astigmatism (D) | 0.46 | 0.48 | −0.02 | 0.05 | −0.12 | 0.07 | −0.49 | .627 |
| Postop refractive astigmatism (D) | −0.45 | −0.92 | 0.47 | 0.08 | 0.31 | 0.63 | 5.84 | .000 |
| Postop subjective astigmatism (D) | −0.28 | −0.69 | 0.41 | 0.09 | 0.22 | 0.60 | 4.38 | .000 |
Paired-Eye Comparison of T0 vs Tx
For patients who received a nontoric IOL (T0) in one eye and a toric IOL of ≥T3 (Tx) in the fellow eye, preoperative corneal astigmatism was significantly higher in the Tx eyes (1.31 ± 0.51 D) compared with the T0 eyes (0.48 ± 0.16 D; P < .001), as expected (Table 3).
At 3 months, the mean spherical equivalent did not differ between groups (0.05 ± 0.33 D in T0 vs 0.12 ± 0.30 D in Tx; P = .454). However, the mean refractive astigmatism (0.92 ± 0.32 D vs 0.53 ± 0.33 D; P < .001) and subjective astigmatism (0.69 ± 0.33 D vs 0.39 ± 0.32 D; P = .002) were both significantly lower in Tx eyes. UDVA was better in Tx eyes (0.04 ± 0.18) than in T0 eyes (0.08 ± 0.15), which showed a trend toward statistical significance (P = .060) (Table 5).
Table 5.
Comparative outcomes: Tx group vs T0 group
| Variables | Tx group mean | T0 group mean | Difference of means | Standard deviation | 95% CI lower limit | 95% CI upper limit | T value | P value |
| Postop UDVA (logMAR) | 0.04 | 0.08 | −0.04 | 0.11 | −0.09 | 0.00 | −1.97 | .060 |
| Postop spherical equivalent (D) | 0.12 | 0.05 | 0.06 | 0.43 | −0.11 | 0.24 | 0.76 | .454 |
| Preop corneal astigmatism (D) | 1.31 | 0.48 | 0.83 | 0.51 | 0.62 | 1.04 | 8.07 | <.001 |
| Postop refractive astigmatism (D) | −0.53 | −0.92 | 0.40 | 0.41 | 0.23 | 0.56 | 4.87 | <.001 |
| Postop subjective astigmatism (D) | −0.39 | −0.69 | 0.31 | 0.45 | 0.12 | 0.49 | 3.39 | .002 |
Astigmatism Correction With T2 vs Tx
In the T2 group, preoperative corneal astigmatism was ≤0.25 D in 16%, ≤0.50 D in 60%, ≤0.75 D in 92%, and ≤1.0 D in 100% of the eyes (Figure 1, A). By contrast, the Tx group had corresponding percentages of 0%, 4%, 8%, and 32%, respectively (Figure 1, B).
Figure 1.
Comparison of astigmatism correction between T2 and ≥T3 toric IOLs. A: Cumulative distribution of preoperative corneal astigmatism and postoperative refractive astigmatism (corneal plane) in the T2 group. The vertical axis represents the cumulative percentage of eyes, and the horizontal axis represents the magnitude of astigmatism. The red area shows preoperative corneal astigmatism, and the blue area shows postoperative refractive astigmatism (converted to the corneal plane). Postoperatively, 56% of eyes had ≤0.25 D, 76% had ≤0.50 D, and 96% had ≤0.75 D refractive astigmatism. B: Cumulative distribution of preoperative corneal astigmatism and postoperative refractive astigmatism (corneal plane) in the Tx group. The vertical axis represents the cumulative percentage of eyes, and the horizontal axis represents the magnitude of astigmatism. The red area shows preoperative corneal astigmatism, and the blue area shows postoperative refractive astigmatism (converted to the corneal plane). Postoperatively, 36% of eyes had ≤0.25 D, 68% had ≤0.50 D, and 92% had ≤0.75 D refractive astigmatism. C: Double-angle plots of preoperative corneal astigmatism and postoperative refractive astigmatism in the T2 group. The square ■ indicates the centroid, the red ellipse indicates its 95% confidence ellipse, and the blue ellipse represents the mathematical 95% confidence ellipse encompassing all eyes. Both ellipses are small preoperatively and postoperatively, with the centroid located closer to the coordinate origin (0, 0) postoperatively. The positive x-axis represents against-the-rule astigmatism, the negative x-axis represents with-the-rule astigmatism, and the y-axis represents oblique astigmatism. Each ring corresponds to 1.0 D. D: Double-angle plots of preoperative corneal astigmatism and postoperative refractive astigmatism in the Tx group. Unlike the T2 group, both the overall 95% confidence ellipse (blue) and centroid ellipse (red) are larger preoperatively; however, both decreased in size postoperatively, with the centroid shifting closer to the coordinate origin (0,0).
Postoperatively, refractive astigmatism in the T2 group was reduced to ≤0.25 D in 56%, ≤0.50 D in 76%, and ≤0.75 D in 96% of the eyes (Figure 1, A). In the Tx group, the respective proportions were 36%, 68%, and 92% (Figure 1, B).
In the double-angle vector analysis, the 95% confidence ellipses for both the entire sample and the centroid were small for the T2 group, with the centroid shifting closer to the coordinate origin (0,0) postoperatively (Figure 1, C). For the Tx group, the preoperative ellipses were larger, although postoperatively both the overall and centroid ellipses decreased in size, with the centroid also shifting closer to the origin (Figure 1, D). Figure 1 summarizes the quantitative parameters such as centroid shift magnitude and ellipse area.
DISCUSSION
This study demonstrated that low-cylinder-power toric IOL (T2 model) implantation significantly reduced postoperative refractive and subjective astigmatism compared with nontoric IOLs (T0) in eyes identified as eligible for a low-cylinder-power toric IOL, resulting in superior UDVA. In the paired-eye analyses, the eyes implanted with a nontoric IOL (T0) exhibited greater residual astigmatism and worse visual function compared with their fellow eyes implanted with higher-cylinder-power toric IOLs (≥T3). In addition, the vector-based analysis showed that the pattern and magnitude of astigmatism correction achieved with the T2 model were comparable with those observed with higher-cylinder-power toric IOLs, with postoperative centroids and confidence ellipses similarly shifting toward the coordinate origin. Taken together, these findings confirm that the low-cylinder-power toric IOL addresses an unmet clinical need by providing effective correction for low levels of corneal astigmatism.
Before the availability of a low-cylinder-power toric IOL, many eyes with low corneal astigmatism received a nontoric IOL, leaving residual astigmatism that could compromise postoperative visual quality. This study results not only corroborated this trend but also demonstrated that low-cylinder-power toric IOL implantation offers clear benefits in such cases. Notably, 96% of the T2 eyes achieved ≤0.75 D postoperative refractive astigmatism, as determined by Astigmatism Double-Angle Plot analysis, underscoring the clinical efficacy of a low-cylinder-power toric IOL in low-astigmatism eyes.
The recommended range for T2 application has generally been considered for 0.75 to 1.50 D corneal astigmatism, and this range remains widely accepted.5,13 However, with the release of the updated Barrett toric calculator in the IOLMaster 700, T2 candidacy has been extended to eyes with corneal astigmatism as low as 0.163 to 0.941 D (Table 2). This is broader and more aggressive than earlier thresholds, particularly for eyes with against-the-rule astigmatism, where even the Baylor nomogram recommends toric correction starting from 0.40 D.14 The present outcomes support this expanded indication, which showed favorable visual results with low-cylinder-power toric IOL implantation in such eyes.
Epidemiological studies have reported that approximately 20% to 25% of patients with cataract present with ≤0.50 D corneal astigmatism, 15% to 20% with ≥1.50 D, and the remaining 50% to 60% fall within the intermediate range 0.50 to 1.50 D.15,16 A randomized fellow-eye comparison study evaluated visual outcomes in eyes with 0.75 to 1.50 D corneal astigmatism, although the mean preoperative astigmatism in that study was relatively higher than that in our cohort (1.16 D in the toric group and 1.11 D in the nontoric group).5 The American Academy of Ophthalmology also recommends toric IOLs for eyes with ≥0.75 D preoperative corneal astigmatism.17 Contrastingly, our study used the updated toric calculator, which identified candidacy for toric IOL implantation at lower corneal astigmatism levels than those previously reported. The present findings demonstrated low-cylinder-power toric IOL's effectiveness for low corneal astigmatism levels from multiple perspectives.
This study has inherent limitations. First, although mirror-image adjustments were applied to left-eye data, intereye correlations and patient-specific binocular visual processing could not be fully accounted. Nevertheless, the paired-eye comparison between the T0 and Tx groups provided a clinically meaningful model for assessing individual tolerance to astigmatism, demonstrating that residual astigmatism was consistently greater in the T0 eyes than in the Tx eyes. Second, the comparison between T0 and T2 was not randomized. Nonrandomized, historically defined comparators may limit the validity and generalizability of the findings. As T2 was expected to be superior for low astigmatism correction, randomization would not have been ethically feasible; therefore, the historical T0 group was used as a comparator. Third, our study reports outcomes at 3 months postoperatively. Although this interval is generally sufficient to capture refractive stability, it does not allow evaluation of long-term toric IOL rotation or stability, which are particularly relevant in toric lens studies. The Clareon toric IOL is relatively new and published evidence currently extends only into the early postoperative period; however, the available data indicate rotational stability comparable with the AcrySof toric platform.18 Multiple studies have demonstrated stable alignment for 1 to 2 years, and vector-based analyses of AcrySof toric IOLs have shown durable refractive stability for 5 to 8 years.19–21 These findings support the expectation that the early rotational stability observed in this study is consistent with the established behavior of this IOL platform, although continued Clareon-specific follow-up remains important. Fourth, different instruments were used for preoperative (IOLMaster 700) and postoperative (autorefractor-keratometer) keratometry. As these devices rely on distinct optical principles and measurement zones, small systematic differences in corneal astigmatism values can occur. However, this limitation applied equally to all study groups, and the primary refractive outcomes were based on manifest refraction rather than postoperative keratometry; therefore, it does not affect interpretation of the main findings. Nevertheless, caution is warranted when comparing preoperative and postoperative corneal astigmatism values. Finally, no with-the-rule cases were included, reflecting the case distribution at our institution. Future studies with larger, randomized cohorts, including a broader spectrum of astigmatism subtypes and extended follow-up periods to assess rotational stability and durability of refractive outcomes, are warranted.
Toric IOLs were originally developed to correct moderate-to-high corneal astigmatism (≥1.50 D). Owing to the introduction of low-cylinder-power toric IOL, the lower boundary of toric correction has effectively been extended, and this study demonstrated that even lower levels of astigmatism can be effectively treated. Expanding the indication for low-cylinder-power toric IOL may therefore improve visual outcomes in a large proportion of patients with cataract worldwide.
The low-cylinder-power toric IOL was effective in reducing residual astigmatism and improving UDVA in eyes with low levels of corneal astigmatism. These findings highlight the clinical value of low-cylinder-power toric IOL implantation in patients who were previously outside the candidacy range for toric IOLs. Broader application of toric correction at lower astigmatism levels may significantly improve functional vision for a large proportion of patients with cataract. Further studies with larger cohorts are warranted to confirm these results and refine the indications for low-cylinder-power toric IOLs.
WHAT WAS KNOWN
Toric IOLs correct moderate-to-high corneal astigmatism (≥1.50 D) and improve uncorrected visual outcomes.
Low corneal astigmatism (<1.50 D) was often left uncorrected with nontoric lenses because the availability of a low-cylinder-power toric IOL varied greatly across countries and remains unavailable in the United States.
The effectiveness of low-cylinder-power toric IOL in real-world practice for low astigmatism has not been systematically evaluated.
WHAT THIS PAPER ADDS
Implantation of a low-cylinder-power toric IOL significantly reduced postoperative refractive and subjective astigmatism compared with nontoric lenses in eyes that would have been eligible for a low-cylinder-power toric IOL.
UDVA was significantly better in eyes implanted with low-cylinder-power toric IOLs compared with nontoric lenses.
Low-cylinder-power toric IOLs provided effective correction of low corneal astigmatism, expanding the clinical range of toric correction.
Footnotes
Presented at the 37th Asia-Pacific Association of Cataract and Refractive Surgeons (APACRS) Annual Meeting, Ahmedabad, India, August 2025.
Disclosures: None of the authors have any financial or proprietary interest in any material or method mentioned.
First author:
Yoshihiko Ninomiya, MD
Department of Ophthalmology, Yukioka Hospital, Osaka, Japan
Contributor Information
Yayoi Muraguchi, Email: yk.yukioka.ort@gmail.com.
Mutsumi Fuchihata, Email: mutsumifuchihata@gmail.com.
REFERENCES
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