Global axial length centile charts: the new standard for myopia management?

Monitoring axial length provides valuable insight into ocular growth and is an important tool for assessing myopia development and progression. However, without appropriate context, that number alone cannot tell us whether a child’s ocular growth is within or outside the expected range. Comparing axial length measurements against centile charts provides this important clinical context. A new published paper from the International Consortium for Refractive Error and Myopia in Children (CREAM-kids) has pooled data from East Asia, Europe and Australia for the first time, including data from 20 paediatric cohort studies, with over 147,000 individual patients and almost 600,000 axial length measurements.¹  Along with their evident value for research, these new global axial length centile charts can help clinicians identify fast axial elongation, track growth trajectories over time and support clinical decision-making in myopia management.

As axial length has become an increasingly important measure in myopia management, having appropriate reference data can provide valuable context for interpreting an individual child’s measurements. Global axial length centile charts¹  provide a reference framework for interpreting a child’s axial length in relation to peers of the same age, sex and geographic region. Similar in concept to paediatric height and weight charts, they show how axial length is distributed across childhood and adolescence, allowing an individual child’s measurement and ocular growth trajectory to be compared with the wider population. 

The axial length centile charts plot the 3rd, 15th, 50th, 85th and 97th centiles, aligned with World Health Organization (WHO) methodology, and provide a picture of how axial length varies with age across different populations. Separate curves are provided by sex and region, covering ages 6–18 years for East Asian children and 6–21 years for European and Australian children. Across the dataset, axial length measurements ranged from 16.11 to 30.16 mm.

Boys have longer eyes than girls, but similar growth rates

Boys had longer axial lengths than girls across all regional groups, with an average difference of 0.54 mm in East Asian children and 0.46 mm in European and Australian children. Despite these differences in absolute axial length, the rates of axial growth were similar between boys and girls.

East Asian children have longer eyes to start with

East Asian children had longer axial lengths than European and Australian children across every centile. In fact, the East Asian 50th centile approximately aligned with the 85th centile for European and Australian children. For girls aged 7 years, the median axial length was 22.67 mm in East Asia compared with 22.35 mm in Europe and Australia, a difference of 0.32 mm. By age 18, these values were 24.36 mm and 23.31 mm respectively, widening the difference to 1.05 mm. At the 97th centile, the regional difference increased from 0.50 mm at age 7 to 1.27 mm at age 18.

East Asian pre-teen children show the fastest eye growth

The charts also reveal differences in the timing and rate of ocular growth. These regional differences were most apparent between 7 and 13 years of age, when East Asian children showed faster axial elongation across the centiles. At the 50th centile, for example, axial growth in boys was 0.24 mm/year in East Asia compared with 0.13 mm/year in Europe and Australia. From ages 14–18 years, axial growth slowed substantially in both regions and the difference between them narrowed; at the 50th centile, growth slowed to 0.05 mm/year in East Asian boys and 0.03 mm/year in European and Australian boys.

These differences by age, sex and region highlight why appropriate reference data are important when interpreting an individual child’s axial length. The centile charts allow clinicians to place a child’s measurement within this broader context, comparing their axial length and ocular growth with peers of the same age, sex and region. In this way, the charts can provide a useful benchmark for interpreting axial length measurements and following ocular growth over time. For a child with myopia, tracking along the same or towards a reduced centile growth curve over time could likely indicate a favourable myopia management result.²  Clinical judgement is required, though, given that a specific axial centile line may combine both emmetropic and myopic eyes and so could under-estimate myopic eye growth in some children.³  In practice, children requiring myopia control are generally within the highest centile groups (>85^th Centile), where there is little mixing with emmetropic eyes. Importantly, refractive error centile curves do not suffer from the same problem as axial length centile curves as refractive category is built into those curves.⁴ 

It is important to note that these charts are region-specific, not ethnicity-specific. For example, a child of East Asian ethnicity living in Australia would be most relevant to the European + Australian charts, not the East Asian charts. The paper states that “ethnicity-specific centile charts were not developed as… the effect of ethnicity on axial length likely varies across regions, and the centile charts are intended for universal use within a region, without being complicated by an assessment of an individual’s ethnicity.” This approach is said to align with WHO growth reference standards. 

There is another important distinction in how the charts should be interpreted. These are reference centile charts, not growth standards. Like the WHO growth references for school-age children, they describe how axial length is actually distributed in school and population-based cohorts of myopic and non-myopic children. A child’s centile is therefore a comparison with their peers rather than a diagnosis in itself, and its clinical value comes from identifying a child’s current status and tracking how that position changes over time.

Centile data is increasingly being incorporated into clinical software to support interpretation at the individual patient level. Ocumetra’s mEYE® Suite integrates axial length and refraction centile charts⁵  into its myopia management platform. Its underlying global database extends beyond the published charts, with additional European and North American data, so a child’s axial length and refraction measurements can be benchmarked against relevant reference data and plotted over time to track progression (see image below). This visual approach turns a single measurement into something parents can readily understand. Rather than hearing that their child’s eye is “24.5 mm long”, parents can see where their child sits relative to peers of the same age, how they are changing over time, and what that trajectory may mean for future myopia. This helps the practitioner explain the child’s individual risk, make a clear case for early intervention, and later show whether treatment is working, which supports informed decision making and ongoing engagement with the management plan.

Centile charts turn an isolated measurement into a meaningful comparison with peers of the same age, sex and region, and transform repeated measurements into a trajectory that can guide management decisions and help parents understand their child’s risk. They describe population distributions rather than defining healthy or unhealthy growth, so are best interpreted alongside refraction, refraction centile charts and clinical judgement. Clinicians should also check that any centile charts they use are built on large, representative reference data that reflects the children they see, as charts derived from small or narrow samples may misclassify a child’s growth.  As global centile charts are integrated into some clinical tools such as Ocumetra’s mEYE® Suite, they make robust population reference data accessible and practical for everyday myopia management.