Abstract
Purpose
To evaluate anisometropia at age 7 years after bilateral secondary intraocular lens (IOL) implantation in children with pediatric aphakia and to identify factors associated with long-term refractive symmetry.
Design
A prospective observational cohort study.
Participants
This study was conducted from 2014 to 2023 at a single center. Of 251 eligible children, 158 (316 eyes) who underwent lensectomy before age 2 and secondary IOL implantation between ages 2 and 6 were included.
Methods
Participants were grouped by age at secondary IOL implantation: 2 to <3 years, 3 to <4 years, 4 to <5 years, and 5 to <6 years. Demographic and clinical data were collected, and refractive outcomes at postoperative 1 month and age 7 years were analyzed. All refractive outcomes were expressed as spherical equivalent (SE), calculated as the sphere plus half of the cylinder (SE = sphere + ½ cylinder).
Main Outcome Measures
Interocular anisometropia at age 7 years, defined as the absolute interocular difference in SE.
Results
At postoperative month 1, 77.2% of children had anisometropia <1.0 D. By age 7 years, this proportion decreased to 52.5%, and significant differences in anisometropia distribution were observed among age-at-implantation groups (P = 0.035). In multivariable analyses, earlier age at secondary IOL implantation (β = –0.260; 95% confidence interval [CI], –0.386 to –0.134; P < 0.001), greater interocular axial length difference at implantation (β = 0.330; 95% CI, 0.033–0.628; P = 0.030), and greater early postoperative anisometropia (β = 0.355; 95% CI, 0.079–0.631; P = 0.012) were independently associated with greater anisometropia at age 7 years.
Conclusions
Interocular anisometropia tends to increase during childhood after bilateral secondary IOL implantation and is influenced by implantation timing, interocular axial length asymmetry, and early postoperative refractive status. Minimizing early postoperative anisometropia may be important for optimizing long-term refractive symmetry, and delayed secondary IOL implantation may be considered in children with marked interocular axial length asymmetry.
Financial Disclosure(s)
The authors have no proprietary or commercial interest in any materials discussed in this article.
Keywords: Anisometropia, Pediatric cataract, Secondary intraocular lens implantation
Pediatric cataract remains a leading cause of childhood visual impairment worldwide, and early surgical intervention is critical to prevent amblyopia.1,2 In infants and young children, primary intraocular lens (IOL) implantation is often deferred because of ocular growth, refractive unpredictability, and concerns about postoperative complications.3 Consequently, many children are managed with aphakia initially and undergo secondary IOL implantation later in childhood. The optimal timing of secondary IOL implantation in pediatric aphakia remains controversial.4 Previous studies have primarily focused on visual acuity and complication rates, with limited data on long-term binocular refractive outcomes.5
Anisometropia is a major risk factor for amblyopia and impaired binocular vision in children.6 Significant anisometropia may also result in intolerance to spectacle correction and increase the risk of strabismus. However, the factors associated with anisometropia after bilateral secondary IOL implantation have not been well characterized. Understanding these factors may help inform the optimal timing of secondary IOL implantation and guide postoperative management.
In this study, we aimed to evaluate anisometropia at 7 years of age in children with bilateral aphakia who underwent bilateral secondary IOL implantation between ages 2 and <6 years. The findings may provide evidence to guide the optimal timing and perioperative management of secondary IOL implantation in pediatric cataract.
Methods
This prospective cohort study (Childhood Cataract Program of the Chinese Ministry of Health, CCPMOH) was conducted at Zhongshan Ophthalmic Center, Sun Yat-sen University, China, from January 2014 to January 2023. The study protocol was approved by the Institutional Review Board of Zhongshan Ophthalmic Center and adhered to the Declaration of Helsinki and STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) reporting guidelines.7 Written informed consent was obtained from the parents or legal guardians of all participants.
Participants
Children with bilateral pediatric cataract who underwent primary lensectomy before 2 years of age were screened for eligibility. Eligible eyes had dense central lens opacities (>3 mm) and no anterior or posterior segment abnormalities.
Exclusion Criteria: Patients were excluded if they (1) did not undergo secondary IOL implantation between 2 and 6 years of age; (2) presented with ocular malformations, including microphthalmia, microcornea, persistent fetal vasculature, or other significant anterior or posterior segment anomalies; (3) had elevated intraocular pressure or a diagnosis of glaucoma prior to cataract surgery; (4) experienced ocular trauma before the age of 7; (5) developed newly diagnosed vision-threatening conditions unrelated to cataract surgery during follow-up, such as inherited retinal disorders; or (6) lacked informed consent from legal guardians. Of 251 screened children, 158 met the inclusion criteria and were enrolled (Fig 1).
Figure 1.
Flowchart of study participants' inclusion and exclusion. COVID-19 = coronavirus disease 2019; IOL = intraocular lens.
Surgical Procedure
All surgeries were performed under general anesthesia by 2 experienced ophthalmologists (Y.L. and Weirong C.). Primary lensectomy consisted of lens aspiration or phacoemulsification, posterior capsulotomy, and anterior vitrectomy using a standardized technique. Secondary IOL implantation was preferentially performed in the capsular bag. The capsular bag was reopened using radiofrequency diathermy or a cystotome-based technique previously described. After removal of residual cortical material, a foldable IOL was implanted in the capsular bag.
Intraocular lens power selection followed the “rule of 7 – age in years” strategy8 to target mild postoperative hyperopia to account for ocular growth (+5.0 D at age 2, +4.0 D at age 3, +3.0 D at age 4, and +2.0 D at age 5). Intraocular lens power was calculated using the SRK/T formula. Intraocular lens models included Rayner 920H/970C (Rayner), SA60AT (Alcon), and PCB00/AR40e (Johnson & Johnson). As a standard protocol, the same IOL model was implanted in both eyes of each patient whenever possible to ensure intraindividual consistency. Postoperative therapy included topical corticosteroids, antibiotics, and nonsteroidal anti-inflammatory agents.
Data Collection and Outcome Measurement
Baseline demographic and clinical data were collected prospectively. The child's sex was reported by guardians. Preoperative evaluations included systemic and ocular history, slit-lamp examination, and intraocular pressure measurement using Goldmann applanation or Icare rebound tonometry (Icare TA01i; Icare Finland Oy). Before secondary IOL implantation, axial length (A-scan ultrasonography or IOL-Master 500/700; Carl Zeiss Meditec), anterior segment imaging, and corneal endothelial cell density (Topcon SP-2000P; Topcon) were assessed.
Participants were examined at 1 day, 1 week, and at 1, 3, 6, and 12 months postoperatively, and annually thereafter. Examinations included best-corrected visual acuity, slit-lamp biomicroscopy, intraocular pressure measurement, and documentation of adverse events and additional interventions. Visual acuity was assessed using grating acuity in younger children and ETDRS tumbling-E charts at 4 m in children aged ≥4 years.
Refraction was assessed using age-appropriate techniques: retinoscopy for children <4 years and subjective refraction for those aged ≥4 years, depending on cooperation. All refractive outcomes were expressed as spherical equivalent (SE), calculated as the sphere plus half of the cylinder (SE = sphere + ½ cylinder). Spectacles were prescribed within 1 month after surgery, targeting distance emmetropia with a +2.50 D near addition. Anisometropia was defined as the absolute interocular difference in SE.
Participants were categorized into 4 groups based on age at secondary IOL implantation (2 to <3, 3 to <4, 4 to <5, and 5 to <6 years). The primary outcome was anisometropia at age 7 years. Secondary outcomes included factors associated with anisometropia at age 7 years.
Statistical Methods
Statistical analyses were performed using SPSS software (SPSS Statistics for Macintosh version 26.0; IBM). Continuous and normally distributed variables were presented as mean ± standard deviation, whereas nonnormally distributed variables were summarized as median with interquartile range (IQR). Categorical variables were expressed as frequencies and percentages. Baseline demographic and ocular characteristics among the 4 groups defined by age at secondary IOL implantation were compared using the Kruskal–Wallis test for nonnormally distributed variables, and the χ2 test or Fisher exact test for categorical variables, as appropriate. Interocular anisometropia was defined as the absolute difference in SE between the 2 eyes. The distribution of anisometropia at postoperative month 1 and age 7 years across the 4 age groups was compared using Fisher exact test. To identify factors associated with anisometropia at age 7 years, multivariable linear regression analysis was performed with anisometropia at age 7 years as the dependent variable. Regression coefficients (β) with 95% confidence intervals (CIs) were reported. A 2-sided P value <0.05 was considered statistically significant.
Results
Baseline Characteristics and Clinical Information
A total of 158 children (316 eyes) with bilateral pediatric cataract were included in the final analysis. The median (IQR) age at primary lens extraction was 5.6 (4.0–7.8) months, and the median (IQR) age at secondary IOL implantation was 4.3 (3.1–5.3) years. Participants were stratified into 4 groups according to age at secondary IOL implantation: 2 to <3 years (n = 34), 3 to <4 years (n = 39), 4 to <5 years (n = 32), and 5 to <6 years (n = 53).
The mean axial lengths before secondary IOL implantation were 22.00 ± 1.9, 22.3 ± 1.7, 23.0 ± 1.8, and 23.1 ± 2.2 mm across the 4 groups, respectively. The median (IQR) absolute interocular axial length differences were 0.2 (0.1–0.4), 0.2 (0.1–0.5), 0.5 (0.1–0.9), and 0.3 (0.1–0.8) mm, with a significant between-group difference (P = 0.049). The mean keratometry before secondary IOL implantation were 43.9 ± 1.7, 44.2 ± 1.7, 44.6 ± 2.2, and 44.3 ± 2.6 D, respectively. The median (IQR) absolute interocular keratometric differences were 0.4 (0.1–1.0), 0.4 (0.2–0.8), 0.5 (0.2–0.7), and 0.6 (0.2–0.9) D, with no significant difference among groups (P = 0.11). Other baseline demographic and ocular characteristics are summarized in Table 1.
Table 1.
Demographic and Ocular Characteristics of Study Participants According to Age at Secondary IOL Surgery
| Group by Age at Secondary IOL Surgery |
P Value | |||||
|---|---|---|---|---|---|---|
| 2 to <3 Yrs | 3 to <4 Yrs | 4 to <5 Yrs | 5 to <6 Yrs | Total | ||
| N, study participants/eyes | 34/68 | 39/78 | 32/64 | 53/106 | 158/316 | NA |
| Sex, Male/Female (%) | 24 (70.6)/10 (29.4) | 25 (64.1)/14 (35.9) | 22 (68.8)/10 (31.2) | 32 (60.4)/21 (39.6) | 103 (65.2)/55 (34.8) | 0.50∗ |
| Age at lens extraction | ||||||
| <3 mo, study participants (%) | 1 (3.0) | 5 (12.8) | 2 (6.3) | 5 (9.4) | 13 (8.2) | NA |
| 3 to <6 mo, study participants (%) | 20 (58.8) | 14 (35.9) | 12 (37.5) | 25 (47.2) | 71 (45.0) | NA |
| 6 to <12 mo, study participants (%) | 13 (38.2) | 17 (43.6) | 12 (37.5) | 16 (30.2) | 58 (36.7) | NA |
| 12 to <24 mo, study participants (%) | 0 (0) | 3 (7.7) | 6 (18.7) | 7 (13.2) | 16 (10.1) | NA |
| Median (IQR) in months | 5.2 (4.1–7.3) | 6.0 (4.0–7.6) | 6.3 (4.5–9.5) | 5.6 (4.0–9.2) | 5.6 (4.0–7.8) | 0.50† |
| Age at secondary IOL implantation | ||||||
| Median (IQR) in yrs | 2.4 (2.2–2.7) | 3.4 (3.2–3.6) | 4.6 (4.4–4.8) | 5.5 (5.3–5.7) | 4.3 (3.1–5.3) | NA |
| Axial length at secondary IOL implantation | ||||||
| Mean ± SD, mm | 22.00 ± 1.9 | 22.3 ± 1.7 | 23 ± 1.8 | 23.1 ± 2.2 | 22.7 ± 2.0 | NA |
| Interocular difference in axial length at secondary IOL implantation (|R–L|) | ||||||
| Median (IQR), mm | 0.2 (0.1–0.4) | 0.2 (0.1–0.5) | 0.5 (0.1–0.9) | 0.3 (0.1–0.8) | 0.3 (0.1–0.7) | 0.049† |
| Mean keratometry at secondary IOL implantation | ||||||
| Mean ± SD, D | 43.9 ± 1.7 | 44.2 ± 1.7 | 44.6 ± 2.2 | 44.3 ± 2.6 | 44.3 ± 2.2 | NA |
| Interocular difference in mean keratometry at secondary IOL implantation (|R–L|) | ||||||
| Median (IQR), D | 0.4 (0.1–1.0) | 0.4 (0.2–0.8) | 0.5 (0.2–0.7) | 0.6 (0.2–0.9) | 0.5 (0.2–0.8) | 0.11† |
| IOL power (D), mean ± SD | 20.9 ± 5.3 | 20.1 ± 5.4 | 18.9 ± 5.1 | 19.7 ± 6.6 | 19.9 ± 5.8 | NA |
| IOL brand, eyes (%) | ||||||
| SA60AT | 58 (85.3) | 27 (34.6) | 23 (35.9) | 39 (36.8) | 147 (46.5) | NA |
| Rayner 970C | 2 (2.9) | 17 (21.8) | 11 (17.2) | 31 (29.2) | 61 (19.3) | NA |
| Rayner 920H | 4 (5.9) | 20 (25.6) | 25 (39.1) | 28 (26.4) | 77 (24.4) | NA |
| PCB00 | 0 (0) | 2 (2.6) | 2 (3.1) | 4 (3.8) | 8 (2.5) | NA |
| AR40e | 4 (5.9) | 12 (15.4) | 3 (4.7) | 4 (3.8) | 23 (7.3) | NA |
| Nystagmus, study participants (%) | 24 (70.6) | 27 (69.2) | 25 (78.1) | 46 (86.8) | 122 (77.2) | 0.17∗ |
| Strabismus, study participants (%) | 20 (58.8) | 20 (51.3) | 23 (71.9) | 39 (73.6) | 102 (64.6) | 0.11∗ |
| Strabismus surgery, study participants (%) | 3 (8.8) | 0 (0) | 2 (6.3) | 1 (1.9) | 6 (3.8) | 0.16‡ |
IOL = intraocular lens; IQR = interquartile range; NA = not applicable; SD = standard deviation.
Chi-squared test.
Kruskal–Wallis test.
Fisher exact test.
Interocular Anisometropia at Postoperative Month 1 and Age 7 Years
At postoperative month 1, 122 children (77.2%) had an interocular SE difference between ≥0 and <1.0 D, 35 children (22.2%) had a difference between ≥1.0 and <2.5 D, and 1 child (0.6%) had a difference ≥2.5 D. The distribution of interocular SE differences across groups is shown in Table 2, Figure 2, and Figure S1 (available at www.ophthalmologyscience.org), with no significant between-group differences (P = 0.169).
Table 2.
Anisometropia at 1 Mo Postoperatively and at Age 7 Yrs
| Group by Age at Secondary IOL Surgery |
||||||
|---|---|---|---|---|---|---|
| 2 to <3 Yrs (n = 34) | 3 to <4 Yrs (n = 39) | 4 to <5 Yrs (n = 32) | 5 to <6 Yrs (n = 53) | Total (n = 158) | P Value | |
| Postoperative month 1 | ||||||
| 0 D less than or equal to SE difference <1 D, study participants (%) | 23 (67.6) | 32 (82.1) | 22 (68.8) | 45 (84.9) | 122 (77.2) | 0.169∗ |
| 1 D less than or equal to SE difference <2.5 D, study participants (%) | 10 (29.4) | 7 (17.9) | 10 (31.3) | 8 (15.1) | 35 (22.2) | |
| SE difference ≥2.5 D, study participants (%) | 1 (2.9) | 0 (0) | 0 (0) | 0 (0) | 1 (0.6) | |
| Age 7 years | ||||||
| 0 D less than or equal to SE difference <1 D, study participants (%) | 15 (44.1) | 17 (43.6) | 20 (62.5) | 31 (58.5) | 83 (52.5) | 0.035∗ |
| 1 D less than or equal to SE difference <2.5 D, study participants (%) | 11 (32.4) | 20 (51.3) | 11 (34.4) | 20 (37.7) | 62 (39.2) | |
| SE difference ≥2.5 D, study participants (%) | 8 (23.5) | 2 (5.1) | 1 (3.1) | 2 (3.8) | 13 (8.2) | |
IOL = intraocular lens; SE = spherical equivalent.
The bold value represents statistical significance (P < 0.05).
Fisher exact test.
Figure 2.
The violin plots of anisometropia at postoperative month 1 and at age 7 years across the different age groups. The bold horizontal dashed line in the center represents the median, while the upper and lower dashed lines indicate the 75th and 25th percentiles, respectively.
At age 7 years, 83 children (52.5%) had an interocular SE difference between ≥0 and <1.0 D, 69 children (39.2%) had a difference between ≥1.0 and <2.5 D, and 13 children (8.2%) had a difference ≥2.5 D. The distribution of interocular SE differences across groups is presented in Table 2 and Figure 2, and significant between-group differences were observed (P = 0.035).
Factors Associated with Anisometropia at Age 7 Years
In multivariable linear regression analyses, age at secondary IOL implantation (β = –0.260; 95% CI, –0.386 to –0.134; P < 0.001), interocular axial length difference at secondary IOL implantation (β = 0.330; 95% CI, 0.033–0.628; P = 0.030), and postoperative month 1 anisometropia (β = 0.355; 95% CI, 0.079–0.631; P = 0.012) remained independently associated with anisometropia at age 7 years (Table 3). Sex, interocular keratometry difference, nystagmus, strabismus, and glaucoma-related adverse events were not independently associated with anisometropia.
Table 3.
Factors Associated with Anisometropia at Age 7 Yrs
| Variables | β (95% CI) | P Value∗ |
|---|---|---|
| Age at secondary IOL surgery, yrs | –0.260 (–0.386 to –0.134) | <0.001 |
| Sex (male vs. female) | 0.244 (–0.060 to 0.549) | 0.115 |
| Interocular difference in axial length at secondary IOL implantation (|R–L|, mm) | 0.330 (0.033–0.628) | 0.030 |
| Interocular difference in mean keratometry at secondary IOL implantation (|R–L|, D) | 0.088 (–0.125 to 0.300) | 0.416 |
| SE difference at 1 mo (D) | 0.355 (0.079–0.631) | 0.012 |
| Nystagmus (yes vs. no) | 0.228 (–0.163 to 0.619) | 0.251 |
| Strabismus (yes vs. no) | 0.162 (–0.191 to 0.515) | 0.367 |
| Glaucoma-related adverse events (yes vs. no) | 0.009 (–0.393 to 0.411) | 0.965 |
CI = confidence interval; IOL = intraocular lens; SE = spherical equivalent.
Bold values represent statistical significance (P < 0.05).
Multivariable linear regression.
Other Outcomes (Best-Corrected Visual Acuity and Complications)
In our previous publication,5 we reported that best-corrected visual acuity at age 7 years and reinterventions were comparable across all age groups. With the exception of glaucoma-related adverse events, which increased with older age at secondary IOL implantation, no significant differences were observed in other postoperative complications.
Discussion
In this cohort study of children with bilateral pediatric cataract undergoing secondary IOL implantation between 2 and <6 years of age, we observed that interocular anisometropia increased over time and differed significantly among implantation age groups by age 7 years. Earlier age at secondary IOL implantation, greater interocular axial length asymmetry at the time of implantation, and greater early postoperative anisometropia were independently associated with greater anisometropia at age 7 years. In contrast, interocular keratometric asymmetry, sex, nystagmus, strabismus, and glaucoma-related adverse events were not independently associated with long-term anisometropia. These findings indicate that the timing of secondary IOL implantation cannot be determined by chronological age alone and should instead be individualized based on interocular biometric symmetry.
The optimal timing of secondary IOL implantation in pediatric aphakia remains controversial.9 Previous studies have primarily focused on visual acuity outcomes and complication rates, while refractive symmetry has received less attention.5,10,11 The Infant Aphakia Treatment Study12,13 and other longitudinal cohorts demonstrated substantial ocular growth and refractive change during early childhood, supporting delayed IOL implantation to reduce myopic shift and postoperative complications.14 However, these studies did not specifically evaluate interocular refractive symmetry as a primary outcome.
Our findings extend prior work by demonstrating that later secondary IOL implantation is associated with reduced long-term anisometropia, suggesting that ocular growth stabilization and improved biometric predictability may contribute to more symmetric refractive outcomes.15 This observation highlights the importance of considering binocular refractive symmetry in surgical timing decisions.
Several mechanisms may explain the association between implantation age and anisometropia. Younger children exhibit rapid and asymmetric axial elongation during early ocular development, which may amplify interocular differences in refractive outcomes after IOL implantation. Delaying IOL implantation allows axial growth to slow and become more symmetric, thereby improving refractive predictability.
Furthermore, interocular axial length difference at the time of secondary IOL implantation was an independent predictor of anisometropia at age 7 years, underscoring the role of baseline biometric asymmetry in determining long-term refractive outcomes. This finding suggests that biometric symmetry should be considered when planning bilateral secondary IOL implantation, particularly in children with asymmetric ocular growth. In cases with substantial interocular axial length asymmetry, delaying secondary IOL implantation may be a reasonable strategy to reduce the risk of long-term anisometropia.
Early postoperative anisometropia was also strongly associated with anisometropia at age 7 years, indicating that early refractive outcomes may serve as a surrogate marker for long-term refractive symmetry. This finding supports the need for close monitoring of refractive status and binocular visual development, as well as early and proactive optical intervention during the critical period of visual development.
These results have important clinical implications. First, they suggest that the timing of secondary IOL implantation should not follow a fixed age-based threshold but should be tailored according to individual biometric characteristics. Second, interocular axial length asymmetry may be a useful parameter for risk stratification of postoperative anisometropia, potentially guiding surgical planning and postoperative management. Third, early postoperative anisometropia may help identify children who require closer follow-up of refractive status and more careful monitoring of binocular visual development.
The strengths of this study include the relatively large cohort of bilateral pediatric cataract patients, standardized age-based stratification of secondary IOL implantation, and comprehensive assessment of interocular biometric and refractive parameters. The bilateral paired-eye design and multivariable regression analyses allowed us to account for interocular correlation and multiple confounders.
Several limitations should be acknowledged. First, the timing of secondary IOL implantation was not determined according to a fixed protocol in this study and was influenced by multiple factors, including parental preferences, potential difficulties with spectacle use, and adherence to amblyopia treatment. Second, although we prioritized the use of identical IOL models for both eyes to ensure intraindividual consistency, 9 of 158 patients (5.7%) received different IOL types due to some reasons. While these IOLs shared similar optical designs, we cannot entirely rule out the influence of lens material or design variations on refractive outcomes. Third, this was a single-center cohort study, which may limit the generalizability of the findings; further validation in populations from different regions and ethnic backgrounds is warranted. Fourth, although multiple covariates were adjusted for in the analyses, residual confounding cannot be excluded, particularly regarding the complex interactions between refractive status, visual development, and conditions such as strabismus. Fifth, the current analysis focused on the 7-year endpoint rather than the year-by-year refractive trajectory. As this is an ongoing prospective cohort, future work will be directed toward modeling the annual velocity of anisometropia development to identify potential sensitive periods for refractive shifts. Additionally, parental refractive status was not evaluated in this study. While a familial predisposition to anisometropia has been suggested in some populations, our findings focus primarily on the clinical and biometric predictors within a cohort specifically undergoing surgery for congenital cataracts, where surgical timing and ocular growth typically play a more dominant role. Finally, although visual acuity outcomes were reported previously, incorporation of binocular visual function measures, such as stereopsis, would further enhance the clinical relevance of our findings.
Conclusion
Interocular anisometropia after bilateral secondary IOL implantation tends to increase during childhood and is influenced by the timing of implantation, interocular axial length asymmetry, and early postoperative refractive status. The timing of secondary IOL implantation should therefore be individualized rather than determined solely by chronological age, and delayed implantation may be considered in children with substantial interocular axial length asymmetry. Efforts should be made to achieve early postoperative refractive symmetry between the 2 eyes. In children who develop early anisometropia, closer monitoring of binocular visual function and timely intervention may be warranted to support optimal visual development.
Manuscript no. XOPS-D-26-00301.
Footnotes
Supplemental material available atwww.ophthalmologyscience.org.
Disclosure(s):
The Article Publishing Charge (APC) for this article was paid by Guangzhou Major Difficult and Rare Diseases Project.
All authors have completed and submitted the ICMJE disclosures form.
The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Supported by the National Natural Science Foundation of China (82271066) and Guangzhou Major Difficult and Rare Diseases Project (2024MDRD05). The funding organizations had no role in the design or conduct of this study.
HUMAN SUBJECTS: Human subjects were included in this study. This prospective cohort study was conducted at Zhongshan Ophthalmic Center, Sun Yat-sen University, China, from January 2014 to January 2023. The study protocol was approved by the Institutional Review Board of Zhongshan Ophthalmic Center and adhered to the Declaration of Helsinki and STROBE reporting guidelines. Written informed consent was obtained from the parents or legal guardians of all participants.
No animal subjects were used in this study.
Author Contributions:
Conception and design: Hu, Qin, Liu, Lin, Weirong Chen
Data collection: Hu, Wan Chen, Qin, Hui Chen, Zhou, Zhang, Ye, Xia
Analysis and interpretation: Hu, Wan Chen, Qin
Obtained funding: Weirong Chen
Overall responsibility: Hu, Wan Chen, Weirong Chen
Supplementary Data
References
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