Vision and refraction screening in children aged 2 and 3 years old in the Haidian district of Beijing

Objective To investigate the criteria for vision and refraction screening in 2- and 3-year-old children. Methods This was a cross- sectional study of 3 804 children (7 656 eyes) aged 2 and 3 years old from kindergartens in the Haidian district who were selected for vision testing and refractive measurement. Distance vision was tested by the child symbols chart and refraction was measured with the Welch Allyn SureSight with noncycloplegy. Medians M (P25, P75) were used to describe visual acuity and refraction. The children were divided into seven groups based on their sphere and cylinder refraction and the distribution of refraction results was compared between any two groups. Visual acuity lower than 0.4 was considered abnormal. The incidence of abnormal vision in different groups was compared. The children were divided into three groups according to their refraction: normal vision ≥0.6; low vision=0.5; abnormal vision≤0.4, then an analysis of the incidence of refractive error in different vision groups was performed. Comparison of visual acuity in different refractive groups using rank sum test; the incidence of visual acuity and refractive abnormalities was compared using chi square test. Results The M (P25, P75) values for visual acuity were 0.6(0.6, 0.6) in 2-year-olds and 0.6(0.6, 0.8) in 3-year-old children. The visual acuity of 3-year-old children was higher than that of 2-year-old children and the difference was statistically significant(Z=- 10.10, P 0.05). There was a statistically significant difference for sphere refraction(χ2=89.22, P 0.05); while the + 3.00 D or more group was significantly lower (Z=3.53, P 0.05). When the cylinder was - 1.75 D or higher, visual acuity was significantly lower than normal levels (Z=3.31, 4.73, 4.97, P<0.01). When the sphere was higher than +3.00 D and the cylinder was more than -1.75 D, then the abnormal rate of visual acuity was significantly higher than normal levels (χ2=142.20, P<0.01). The abnormal rate of refraction was also significantly higher in the group with abnormal vision(χ2=240.82, P<0.01). Conclusion Refraction screening of 2- and 3- year- old children is helpful in detecting amblyopia early. The criteria for refraction screening: sphere + 3.00 D or higher and cylinder -1.75 D or more. Key words: Refractive errors; Vision screening; Symbols chart; Referral criteria