Aim: To measure and analysis axial length (AL)/corneal radius of curvature (CRC) ratio and other refractive parameters, provide a medical reference range for refractive development evaluation and earlier visual impairment screening of 3 to 4y kindergarten students.
Methods: Between April and June 2017, a total of 4350 participants aged 3- to 4-year-old (8700 eyes) from 10 cluster random sampling kindergartens in Shanghai, Pudong District were involved. According to the measurement and analysis of the unaided visual acuity (VA), AL, CRC, AL/CRC ratio, astigmatism and other refractive parameters, the data distribution and reference range were obtained.
Results: Uncorrected VA of examined children was 0.23±0.08 (logMAR, mean±SD) [95% confidence interval (CI) range ≤0.36]; AL was 22.10±0.79 mm (95%CI 20.55-23.65); CRC was 7.86±0.26 mm (95%CI, 7.35-8.37); AL/CRC ratio was 2.81±0.12 (95%CI, 2.57-3.05). The median of astigmatism was -0.5 D, a total of 56.3% had astigmatism <-0.50 D, 85.3%<-1.00 D, 6.7%>-1.50 D; 71% were astigmatism with the rule. Eye-specific analyses were conducted. Statistical difference of VA was in right and left eyes. There were no significant differences between two eyes of AL, CRC, AL/CRC ratio and astigmatism (P>0.05).
Conclusion: VA and AL/CRC ratio reference could be used to assess refractive development in children and screening uncorrected refractive errors or amblyopia. Astigmatism needs to be considered in the diagnosis.
Keywords: axial length/corneal radius of curvature ratio; children; reference; refractive development; visual impairment.