China Axial Length Study (CALS)

Axial Length Study of Children and Adolescents in Ten Provinces of China

The primary objective of this multi-center, observational study is to establish the reference ranges of axial length in Chinese children and adolescents.

30,000 children aged 3-18 years were examined with cycloplegia to collect their ocular parameters and were all followed up for three years with annual visits.

Study Overview

• Status: Recruiting
• Conditions: Myopia; Child Development; Axial Length

• Study Type: Observational
• Enrollment (Estimated): 30000

Contacts and Locations

• Study Contact: Name: Xun Xu, MD; Phone Number: 86 021-53555032; Email: drxuxun@sjtu.edu.cn
• Study Contact Backup: Name: Xiangui He, PhD; Phone Number: 86 15000755422; Email: xianhezi@163.com

Study Locations

• China
  • Shanghai, China
    • Recruiting
    • Shanghai Eye Disease Prevention and Treatment Center
    • Contact: Xiangui He; Phone Number: 8602153555032; Email: xianhezi@163.com
  • Shanghai Municipality
    • Shanghai, Shanghai Municipality, China, 200040
      • Recruiting
      • Shanghai Eye Disease Prevention & Treatment Center
      • Contact: Xun Xu, MD; Phone Number: 86-13386259538; Email: drxuxun@tom.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 3 years to 18 years (Child, Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Students aged from 3 to 18 years old were recruited from schools to enroll the study.

Description

Inclusion Criteria:

• Aged 3 to 18 years
• Have been lived in the research areas for at least one year, and will not move to other places in the following two years
• Parents or guardians sign an informed consent form, and children over 6 years old need oral consent to participate

Exclusion Criteria:

• Mental diseases, unable to cooperate to complete the eye assessment
• Ophthalmic diseases, inability to cooperate to complete the inspection

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
Myopes; To collect the ocular data among myopic children.
Non-myopes; To collect the ocular data among non-myopic children.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Axial length	Axial length in millimeter was examined by IOL Master	2023-2026

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Axial length elongation	The elongation in millimeter was the difference between two annual visits.	2023-2026

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comparison of visual acuity outcomes obtained by VA charts with different optotypes among children	This outcome measure evaluates differences in uncorrected visual acuity (UCVA) results obtained using HOTV and Tumbling E logMAR charts among children aged 3-15 years.	Baseline vision testing at enrollment (single study visit)

Collaborators and Investigators

• Sponsor: Shanghai Eye Disease Prevention and Treatment Center
• Collaborators: Tongji Hospital; Sichuan Provincial People's Hospital; Shandong University of Traditional Chinese Medicine; People's Hospital of Ningxia Hui Autonomous Region; Affiliated Hospital of Inner Mongolia Minzu University; First Affiliated Hospital of Kunming Medical University; The First Affiliated Hospital of Guangxi Traditional Chinese Medical University; Xinjiang Hospital of Traditional Chinese Medicine

Study record dates

Study Major Dates

• Study Start (Actual): March 10, 2023
• Primary Completion (Estimated): December 31, 2026
• Study Completion (Estimated): December 31, 2026

Study Registration Dates

• First Submitted: March 5, 2023
• First Submitted That Met QC Criteria: March 5, 2023
• First Posted (Actual): March 15, 2023

Study Record Updates

• Last Update Posted (Actual): December 18, 2025
• Last Update Submitted That Met QC Criteria: December 11, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Eye Diseases; Refractive Errors; Myopia
• Other Study ID Numbers: NO.CALS20220101

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No