Objective:To compare cooperation degree and visual acuity difference between Lea Symbols chart and ETDRS chart in Chinese preschool children.

Methods:A prospective self-control study design was performed.Two hundred and forty-one children aged from 42 months to 78 months in Quanzhou Quangang Experimental Kindergarten were enrolled and the mean age was (61.9±10.3) months.Among them, 132 pre-school children had normal refractive index.All children completed comprehensive ophthalmological examinations and measurement of monocular visual acuity using Lea Symbols chart and ETDRS chart.All monocular visual acuity scores were recorded in LogMAR form.This study followed the Declaration of Helsinki and this study protocol was approved by Medical Ethics Committee of The Second Affiliated Hospital of Fujian Medical University (No.2017[62]). Written informed consent was obtained from all guardians before entering the study.

Results:The cooperation degrees of Lea Symbols chart and ETDRS chart were 96.7% and 95.0% in 42-78 months of children, respectively, with no significant difference between the two visual acuity tables (χ²=1.669, P>0.05). The visual acuity measured by Lea Symbols chart was positively correlated with that measured by ETDRS chart (r_s=0.726, P<0.001). The measurement consistency of the two chart was good (Kappa=0.531). Among 132 normal refractive children, the visual acuity level measured by Lea Symbols chart was higher than that measured by ETDRS chart (W=-7.461, P<0.001); the measurement consistency of the two visual acuity chart was good (Kappa=0.467). There was no significant difference between the two charts in measuring the binocular vision difference (W=-0.889, P=0.374); the visual acuity levels of boys measured by Lea Symbols chart and ETDRS chart were higher than those of girls, and the difference was statistically significant (U=-3.352, -4.679; both at P<0.001); the visual acuity values measured by Lea Symbols chart and ETDRS chart were negatively correlated with age (r_s=-0.423, -0.437; both at P<0.001); the visual acuity measured by Lea Symbols chart was higher than that measured by ETDRS chart in different age groups, and the differences were statistically significant (all at P<0.001).

Conclusions:The measurement of visual acuity by Lea Symbols chart and ETDRS chart can be achieved with a high cooperation degree in 42 months and older children.The visual acuity measured by Lea Symbols chart is higher than that measured by ETDRS chart.In the preschool children's vision screening, we should pay attention to the difference between the two kinds of visual charts, and be careful to judge the abnormal vision.