Existing pediatric corneal reference values may have limited applicability across diverse populations because of geographic disparities, inconsistent measurement methods, and gaps in evidence. Corneal thickness, curvature, and diameter generally remained relatively stable after early childhood, although age-, sex-, and ethnicity-related differences varied across studies.
The investigators reviewed 28 studies involving more than 46,000 healthy children younger than 18 years, published between January 2000 and December 2024. Studies were identified through searches of Google Scholar, PubMed, institutional repositories, and reference lists. Eligible studies reported at least 1 corneal measurement in children without additional impairments or comorbidities. Of 520 records initially identified, 373 remained after duplicate removal, and 28 met the inclusion criteria.
The review examined central corneal thickness, corneal curvature, and corneal diameter, along with differences associated with age, sex, race or ethnicity, and geographic location. Central corneal thickness was the most frequently studied variable, assessed in 25 studies involving more than 28,000 children. Corneal curvature was evaluated in 9 studies involving more than 16,000 children, while corneal diameter was examined in 4 studies involving more than 10,000 children. The investigators also assessed differences in measurement technologies and reporting practices.
Central corneal thickness generally remained stable after early childhood, although findings on age-related changes were inconsistent. Some studies reported increases in corneal thickness until approximately age 11 years, whereas others reported decreases with age. Another study found the greatest central corneal thickness among children aged 5 to 9 years. Differences in age distributions, study populations, and measurement techniques may have contributed to the variation in findings.
Evidence of sex-related differences in central corneal thickness was similarly mixed. Several studies reported no statistically significant differences between boys and girls, while others found thicker corneas among boys. Studies examining racial and ethnic variation generally reported thinner corneas among Black children compared with White children. Differences were also observed among Chinese, Malay, Indian, Fars, and Turk children, although findings varied across study populations.
Corneal curvature appeared relatively stable during early childhood, although some studies reported changes during adolescence. Several studies found steeper corneas among girls compared with boys, although age-related findings were inconsistent. Only 1 study examined racial or ethnic differences in corneal curvature, limiting the available evidence on variation across populations.
Corneal diameter also showed relatively little variation across childhood. Most studies reported minimal age-related changes, although 1 study identified a small decrease between ages 7 and 14 years. Evidence of sex-related differences was limited, and none of the included studies evaluated racial or ethnic differences in corneal diameter.
Geographic representation was uneven. Of the 28 studies, 17 (61%) were conducted in Asia, compared with 4 in North America, 2 each in Europe, Africa, and South America, and 1 in Australia. The investigators identified limited representation of African populations, with the 2 African studies including substantially smaller samples than several studies from other regions. This imbalance limited the generalizability of the findings across geographically and ethnically diverse pediatric populations.
Measurement methods also differed considerably. Studies used ultrasound pachymetry, optical coherence tomography, Scheimpflug imaging, automated keratometry, and other technologies to assess corneal variables. Because these technologies use different measurement principles, reported values may not be directly comparable across studies. Reporting practices also varied, with some authors measuring 1 eye, others averaging measurements from both eyes, and some not specifying which eye was assessed.
The review had several limitations. Most included studies used cross-sectional designs, limiting the ability to assess corneal development over time. Differences in measurement technologies, age classifications, demographic reporting, and laterality complicated comparisons. The predominance of Asian study populations and limited representation of other regions further constrained generalizability. The review was also restricted to English-language publications, potentially excluding relevant evidence.
Pediatric corneal measurements should be interpreted in the context of the populations and measurement methods used to establish reference values. The authors emphasized the need for standardized measurement procedures, consistent reporting, and longitudinal investigations involving more geographically and ethnically diverse pediatric populations.
“Overall, this scoping review suggests that the interpretation of corneal variables in children is influenced by demographic, methodological, and geographic factors,” wrote lead study author Nonkazimulo Shabalala, of the University of Limpopo, Polokwane, South Africa, and colleagues.
The authors reported no conflicts of interest.
Source: Clinical Optometry
