Prevalence and Age-Related Changes of Corneal Astigmatism in Patients Undergoing Cataract Surgery in Northern China

Effect of low-degree astigmatism on the objective visual quality

AIM

To evaluate the effect of low-degree astigmatism on objective visual quality through the Optical Quality Analysis System (OQAS).

METHODS

This study enrolled 46 participants (aged 23 to 30y, 90 eyes) with normal or corrected-to-normal vision. The cylindrical lenses (0, 0.5, 0.75, 1.0, and 1.25 D) were placed at the axial direction (180°, 45°, 90°, and 135°) in front of the eyes with the best correction to form 16 types of regular low-degree astigmatism. OQAS was used to detect the objective visual quality, recorded as the objective scattering index (OSI), OQAS values at contrasts of 100%, 20%, and 9% predictive visual acuity (OV100%, OV20%, and OV9%), modulation transfer function cut-off (MTFcut-off) and Strehl ratio (SR). The mixed effect linear model was used to compare objective visual quality differences between groups and examine associations between astigmatic magnitude and objective visual quality parameters.

RESULTS

Apparent negative relationships between the magnitude of low astigmatism and objective visual quality were observed. The increase of OSI per degree of astigmatism at 180°, 45°, 90°, and 135° axis were 0.38 (95%CI: 0.35, 0.42), 0.50 (95%CI: 0.46, 0.53), 0.49 (95%CI: 0.45, 0.54) and 0.37 (95%CI: 0.34, 0.41), respectively. The decrease of MTFcut-off per degree of astigmatism at 180°, 45°, 90°, and 135° axis were -10.30 (95%CI: -11.43, -9.16), -12.73 (95%CI: -13.62, -11.86), -12.75 (95%CI: -13.79, -11.70), and -9.97 (95%CI: -10.92, -9.03), respectively. At the same astigmatism degree, OSI at 45° and 90° axis were higher than that at 0° and 135° axis, while MTFcut-off were lower.

CONCLUSION

Low astigmatism of only 0.50 D can significantly reduce the objective visual quality.

Prevalence data for total corneal astigmatism in cataract patients

PURPOSE

To report the prevalence data for total corneal astigmatism (TCA) in cataract patients.

METHODS

The authors retrospectively collected and analyzed the preoperative biometric data of the patients who underwent cataract surgery in the Department of Ophthalmology, Peking University Third Hospital, from January 2019 to May 2023.

RESULTS

The mean age of the 10817 patients was 71 ± 10 years; the male/female ratio was 4653/6164. The mean TCA obtained by the IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany), the Abulafia-Koch (AK) formula, and the Barrett toric calculator was 1.11 ± 0.81 diopter (D), 1.13 ± 0.75 D, and 1.12 ± 0.74 D respectively, which was significantly greater than the mean standard keratometric (K) astigmatism (0.99 ± 0.75 D) obtained by IOLMaster 700. Against-the-rule (ATR) astigmatism was dominant in all the TCA measurements, and its proportion increased with age. TCA measurements by different methods exhibit high variability, with a total of 1574 (8.9%) data sets from 1016 (9.4%) patients showing a difference larger than 0.5 D in at least one pair of TCA measurements.

CONCLUSION

The use of TCA rather than K astigmatism significantly influenced the choice of intraocular lenses (IOLs) as more patients would be candidates for toric IOLs. It was essential to carefully compare and select TCA obtained with multiple methods for optimal postoperative visual quality.

Comparison of the effect of capsular bend on the rotational stability between 2 toric intraocular lenses

PURPOSE

To compare the effect of capsular bend on the rotational stability between 2 toric intraocular lenses (IOLs).

SETTING

Eye Hospital of Wenzhou Medical University, Hangzhou, Zhejiang Province, China.

DESIGN

Prospective study.

METHODS

Patients with preexisting astigmatism received AcrySof IQ (SN6AT) or TECNIS (ZCT/ZMT) toric IOL during cataract surgery. CASIA2 was used to record the toric IOL axial orientation and capsular bend index (CBI) at the 1-day, 1-week, 1-month, and 3-month interval postoperatively. The postoperative rotational stability and CBI of both models were compared.

RESULTS

A total of 58 eyes from 58 patients were enrolled in this study. The total misalignment of the TECNIS (ZCT/ZMT) group (6.96 ± 5.10 degrees, 7.41 ± 5.19 degrees, 6.93 ± 5.29 degrees, and 6.86 ± 5. 27 degrees) was significantly higher than that of the AcrySof IQ (SN6AT) group (3.55 ± 2.21 degrees, 4.00 ± 2.74 degrees, 3.72 ± 2.72 degrees, and 3.52 ± 2.50 degrees) at all follow-up intervals ( P < .05). The mean rotation of the TECNIS (ZCT/ZMT) group (2.66 ± 2.18 degrees) was significantly greater than that of the AcrySof IQ (SN6AT) group (1.65 ± 1.47 degrees) from 1 day to 1 week postoperatively ( P < .05). The capsular bend formation in the TECNIS (ZCT/ZMT) group was delayed compared with the AcrySof IQ (SN6AT) group ( P < .05, at the 1-week, 1-month, and 3-month interval). The TECNIS (ZCT/ZMT) group showed fibrosis in the peripheral anterior capsule, leading to its stretching away from the IOL surface, while the AcrySof IQ (SN6AT) group exhibited gentle adherence of the anterior capsule to the IOL surface.

CONCLUSIONS

The AcrySof IQ toric IOL (SN6AT) exhibited greater rotational stability than the TECNIS toric IOL (ZCT/ZMT), which may partially result from the delay in capsular bend formation of TECNIS at the 1-day to 1-week follow-up postoperatively.

Rotational stability of plate-haptic toric intraocular lenses in Asian eyes: risk period for intraocular lens rotation and its influencing factors

PURPOSE

To investigate the rotational stability of plate-haptic toric intraocular lenses (IOLs) during 3-month follow-up.

SETTING

Eye and ENT Hospital of Fudan University, Shanghai, China.

DESIGN

Prospective observational study.

METHODS

Patients with cataracts implanted with AT TORBI 709M toric IOLs were enrolled and followed at 1 hour, 1 day, 3 days, 1 week, 2 weeks, 1 month, and 3 months postoperatively. A linear mixed model of repeated measures was applied to investigate the time course of absolute IOL rotation change. The 2-week overall IOL rotation was analyzed in the age, sex, axial length (AL), lens thickness (LT), preexisting astigmatism, and white-to-white subgroups.

RESULTS

A total of 328 eyes of 258 patients were included. The rotation from the end of surgery to 1 hour and 1 day to 3 days was significantly smaller compared with the rotation from 1 hour to 1 day but more than that at other time intervals in the overall group. 2 weeks postoperatively, the mean uncorrected distance visual acuity and remaining positive cylinder were 0.19 ± 0.22 logMAR and 0.60 ± 0.44 diopters, respectively. Significant between-group differences in 2-week overall rotation were found in the age, AL, and LT subgroups.

CONCLUSIONS

Maximum rotation occurred within 1 hour to 1 day postoperatively, and the first 3 days postoperatively was a high-risk period for the plate-haptic toric IOL rotation. Surgeons should make the patients aware of this.

Effect of two different preoperative calculation schemes on visual outcomes of patients after toric intraocular lens implantation

PURPOSE

To compare the postoperative visual outcomes of two different preoperative corneal incision schemes in TECNIS toric intraocular lens (IOL) implantation.

METHODS

In this randomized controlled study, patients with preoperative corneal astigmatism greater than 1.0 diopter (D) were included. These patients were grouped according to the different preoperative schemes: steep-axis group and minimum-residual refractive astigmatism group. The outcome measurements were the residual refractive astigmatism, visual acuity, changes of corneal astigmatism, and high-order aberration at 1 month postoperatively.

RESULTS

This study consisted of 90 eyes (45 eyes steep-axis group, 45 eyes minimum-residual refractive astigmatism group). 1 month after surgery, the refractive astigmatism was statistically lower in the minimum-residual refractive astigmatism group compared with the steep-axis group (0.58 ± 0.40D vs 0.38 ± 0.37D, P = 0.021). The minimum-residual refractive astigmatism group had a smaller difference vector (0.56 ± 0.38D vs 0.36 ± 0.35D; P = 0.047) and a smaller prediction error (0.60 ± 0.44D vs 0.37 ± 0.35D; P = 0.004). In the steep-axis group, corneal astigmatism significantly decreased compared with preoperative value (1.65 ± 0.57D vs 1.17 ± 0.64D; P < 0.001). In the minimum-residual refractive astigmatism group, the changes of corneal astigmatism before and after surgery were not significant. Moreover, total aberration and second astigmatism in ocular aberration were lower in the minimum-residual refractive astigmatism group compared with the steep-axis group (1.86 ± 1.09 vs 1.37 ± 0.95; P = 0.035 and 0.47 ± 0.28 vs 0.31 ± 0.19; P = 0.015, respectively).

CONCLUSION

Minimum-residual refractive astigmatism incision had better astigmatism correction and more accurate prediction. The corneal astigmatism was stable 1 month after surgery. It might lead to better visual quality in the early postoperative stage. Trial registration number for prospectively registered trials: clinicaltrials.gov NCT04006912, 07/02/2019.

Correlation analysis between self-rated treatment effect and diagnosis and treatment of elderly poor cataract patientswith poor financial condition in rural areas of Ganzi Prefecture

OBJECTIVE

To analyze the correlation between self-rated treatment effect and diagnosis and treatment of elderly indigent cataract patients in rural areas of Ganzi Prefecture.

METHODS

In this retrospective study, senior cataract patients admitted in the Ganzi region from March 2018 to November 2021 were included. 495 indigent patients were classified into the poor group, including 400 cases who received surgical treatment and 95 who did not. The 318 patients that were not indigent were classified as the non-poor group. The basic demographic characteristics, treatment, self-assessed treatment effect, and the cost of surgery, blindness rate, and disability rate were compared between the two groups. The correlation between self-assessed treatment effect and treatment condition of patients in the poor group was analyzed by multi-factor unconditional logistic regression.

RESULTS

There were no significant differences in the basic demographic characteristics, self-assessed treatment effect, or postoperative blindness rate between the patients receiving surgery in both groups (P>0.05). The visual acuity of 400 patients after the operation was significantly higher than that before operation (P<0.05). The operation and other costs in the poor group were lower than those of the non-poor group (P<0.05). The elimination rate of disability in the non-poor group was significantly higher than in the poor group (P<0.05). Multivariate regression analysis showed that the level of the hospital, the location of the treatment institution, living alone, education level, and the number of visits were factors affecting the self-rated treatment effect of patients (P<0.05).

CONCLUSION

The self-rated treatment effect of elderly indigent cataract in rural Ganzi Prefecture was closely related to the level of the hospital, the location of treatment institutions, living alone, education level, and the number of visits. Health poverty alleviation programs should be strengthened.

Propensity-matched comparison of postoperative stability and visual outcomes of toric intraocular lens with or without a capsular tension ring and updated meta-analysis

PURPOSE

To assess the contribution of capsular tension ring (CTR) to postoperative stability and visual outcomes of a plate-haptic toric intraocular lens (IOL).

METHODS

This prospective cohort study was performed among patients underwent toric IOL (AT TORBI 709 M) implantation with or without CTR at the Eye and ENT hospital between April 2020 and November 2021. Propensity score matching (PSM) was performed to balance baseline factors. Postoperatively, uncorrected distance visual acuity (UCVA) and residual astigmatism, as well as IOLs' rotation, tilt, and decentration, were analyzed. Grouped multiple linear regression analysis was used to model predictive factors of rotation in each group. Additionally, a meta-analysis of data from 4 publications (284 eyes) and current study was performed to evaluate the effect of CTR co-implantation on toric IOL rotation.

RESULTS

After PSM, 126 eyes from each group were included for further analysis. Postoperatively, UDVA was 0.31 ± 0.38 logMAR and 0.27 ± 0.36 logMAR in the CTR and NCTR groups, respectively (P = 0.441), and residual astigmatism was 0.75 ± 0.52 D and 0.86 ± 0.65 D, respectively (P = 0.139). The rotation of toric IOL was significantly smaller in the CTR group than in the NCTR group (4.63 ± 6.27 vs. 10.93 ± 16.05 degrees, P < 0.001). The regression models of the two groups and the coefficients of LT were significantly different (P < 0.001 and P = 0.001, respectively). Furthermore, the meta-analysis confirmed that CTR co-implantation reduced toric IOL rotation (MD, - 1.59; 95% CI, - 3.10 to - 0.09; P = 0.038).

CONCLUSION

CTR enhances rotational stability of toric IOL by reducing the impact of LT, and CTR co-implantation is recommended in patients with lens thickness (LT) ≥ 4.5 mm, white-to-white (WTW) ≥ 11.6 mm, or high preexisting astigmatism.

Prediction of corneal astigmatism based on corneal tomography after femtosecond laser arcuate keratotomy using a pix2pix conditional generative adversarial network

Purpose

This study aimed to develop a deep learning model to generate a postoperative corneal axial curvature map of femtosecond laser arcuate keratotomy (FLAK) based on corneal tomography using a pix2pix conditional generative adversarial network (pix2pix cGAN) for surgical planning.

Methods

A total of 451 eyes of 318 nonconsecutive patients were subjected to FLAK for corneal astigmatism correction during cataract surgery. Paired or single anterior penetrating FLAKs were performed at an 8.0-mm optical zone with a depth of 90% using a femtosecond laser (LenSx laser, Alcon Laboratories, Inc.). Corneal tomography images were acquired from Oculus Pentacam HR (Optikgeräte GmbH, Wetzlar, Germany) before and 3 months after the surgery. The raw data required for analysis consisted of the anterior corneal curvature for a range of ± 3.5 mm around the corneal apex in 0.1-mm steps, which the pseudo-color corneal curvature map synthesized was based on. The deep learning model used was a pix2pix conditional generative adversarial network. The prediction accuracy of synthetic postoperative corneal astigmatism in zones of different diameters centered on the corneal apex was assessed using vector analysis. The synthetic postoperative corneal axial curvature maps were compared with the real postoperative corneal axial curvature maps using the structural similarity index measure (SSIM) and peak signal-to-noise ratio (PSNR).

Results

A total of 386 pairs of preoperative and postoperative corneal tomography data were included in the training set, whereas 65 preoperative data were retrospectively included in the test set. The correlation coefficient between synthetic and real postoperative astigmatism (difference vector) in the 3-mm zone was 0.89, and that between surgically induced astigmatism (SIA) was 0.93. The mean absolute errors of SIA for real and synthetic postoperative corneal axial curvature maps in the 1-, 3-, and 5-mm zone were 0.20 ± 0.25, 0.12 ± 0.17, and 0.09 ± 0.13 diopters, respectively. The average SSIM and PSNR of the 3-mm zone were 0.86 ± 0.04 and 18.24 ± 5.78, respectively.

Conclusion

Our results showed that the application of pix2pix cGAN can synthesize plausible postoperative corneal tomography for FLAK, showing the possibility of using GAN to predict corneal tomography, with the potential of applying artificial intelligence to construct surgical planning models.

Predictors of Femtosecond Laser-Assisted Arcuate Keratotomy Efficacy for Astigmatism Correction in Cataract Surgery

PURPOSE

To evaluate the predictors related to the efficacy of epithelium- and Bowman membrane-penetrating femtosecond laser-assisted arcuate keratotomy (FSAK) in the treatment of preoperative astigmatism in patients with cataracts and to clarify the predictive role of the incision-to-limbus distance.

METHODS

This retrospective study included patients who underwent femtosecond laser-assisted cataract surgery combined with FSAK using the LenSX platform (Alcon Laboratories, Inc) at Beijing Aier-Intech Eye Hospital from March 2017 to December 2021. The Lenstar LS900 (Haag-Streit, Inc) was used to measure the horizontal corneal diameter, and ImageJ software (National Institutes of Health) was used to measure the vertical corneal diameter and incision-to-limbus distance. Finally, the measured values were converted. Changes in corneal astigmatism before and 3 months after surgery were analyzed using Alpins vector analysis. Correlation analysis and regression analysis were used to evaluate the factors associated with surgically induced astigmatism (SIA) in preoperative ocular biometric parameters.

RESULTS

The study included 94 eyes of 94 patients. The mean target induced astigmatism was 1.36 ± 0.44 diopters (D), SIA was 0.82 ± 0.43 D, and mean difference vector was 0.70 ± 0.40 D. Pearson correlation analysis and univariate regression analysis showed that preoperative corneal astigmatism, arcuate keratotomy arc length, incision-to-limbus distance, and astigmatism type were significant predictors of SIA. Multiple variable regression analysis included parameters such as age, arcuate keratotomy arc length, and incision-to-limbus distance and established a multiple regression model of SIA (all P < .01).

CONCLUSIONS

The incision-to-limbus distance was a significant independent predictor of SIA, and inclusion of this parameter may further improve the accuracy of the nomogram. [J Refract Surg. 2022;38(8):480-486.].

Comparison of Visual Outcomes Between Toric Intraocular Lenses and Clear Corneal Incisions to Correct Astigmatism in Image–Guided Cataract Surgery

Purpose

To compare the astigmatism correction effects of toric intraocular lenses (IOL) and clear corneal incisions during image-guided cataract surgery.

Methods

All patients with regular corneal astigmatism of 0.75–1.5 D underwent cataract surgery and astigmatism correction using the Callisto eye image-guided system. One group had implantation of an AcrySof toric IOL. Another group had implantation of aspheric IOL with 3.0 mm single clear corneal incision (SCCI) on the steep axis. Uncorrected and best-corrected spectacle visual acuity, refraction, and toric IOL axis were evaluated at 1, 4, and 12 weeks postoperatively.

Results

Sixty-eight eyes of 68 patients were included. The mean residual refractive cylinder was 0.34 ± 0.40 D in the toric group and 0.64 ± 0.57 D in the SCCI group. There were no significant differences in residual refractive cylinder, spherical equivalent, uncorrected distance visual acuity (UDVA), and best-corrected spectacle visual acuity (BCSVA) between groups. The percentage of the residual cylinder within ± 0.50 D was 75 and 56% for toric and SCCI cases, respectively (p &gt; 0.1). The mean surgical induced astigmatism vector was 0.61 ± 0.29 D in the SCCI group and 1.04 ± 0.38 D in the toric group. The mean magnitude of error was negative (−0.54 ± 0.48 D) and the correction index was &lt;1.0 (p &lt; 0.05) in SCCI group. At 3 months, all toric IOL alignment errors were within 5 degrees from the intended axis.

Conclusions

Both toric IOL and SCCI can correct low and medium astigmatism effectively with the help of a precise image-guided system.