To analyze the relationship between the developmental eye movement (DEM) test results and the vocabulary size in Chinese children with developmental dyslexia.

A cross-sectional study was conducted.A total of 1 243 fifth grade students from 10 primary schools were enrolled from September to December 2019 in Tianjin, among which there were 664 males and 579 females, with the average age of (10.68+ 0.53) years old.The Chinese vocabulary test and intelligence test were carried out.Eighty-five dyslexic children with subaverage vocabulary size were selected as the experimental group and 54 normal children were selected as the control group.The DEM test was conducted in the two groups, and the vertical time, the horizontal adjustment time, the ratio of horizontal to vertical time and the total number of errors were recorded and analyzed.The differences in positive rate of dyslexia, various DEM test indicators between different genders and different groups were analyzed.The correlations between vocabulary size and vertical time, horizontal adjustment time, the ratio of horizontal to vertical time and the total number of errors were analyzed.This study protocol adhered to the Declaration of Helsinki and was approved by an Ethics Committee of School of Optometry, Tianjin Vocational Institute (No.ysgxyll001). Written informed consent was obtained from the guardian of each subject.

The total positive rate of dyslexia was 6.83%(85/1 243), and the positive rate of 9.33%(62/664) in boys was higher than 3.97%(23/579) in girls, with a significant difference between them(χ²=13.974, P<0.001). There were no statistically significant differences in age, vocabulary size, vertical time, horizontal adjustment time, and the ratio of horizontal to vertical time between different genders in the control group (all at P>0.05). The vocabulary size of girls in the experimental group was larger than that of boys, showing a statistically significant difference (t=-2.259, P=0.027). There was no significant difference in age, vertical time, horizontal adjustment time, and the ratio of horizontal to vertical time (all at P>0.05). The vertical time and horizontal adjustment time of the experimental group were longer than those of the control group, and the differences were statistically significant (t=-4.848, -4.297; both at P<0.001). There was no statistically significant difference in the ratio of horizontal to vertical time between the two groups (t=0.126, P=0.900). The total number of errors was 0(0, 1) in the experimental group, which was higher than the control group 0(0, 0), with a significant difference between them (H=1.979, P=0.001). The vocabulary size of students in the two groups was negatively correlated with the vertical time, horizontal adjustment time and the total number of errors (r=-0.397, P<0.001;r=-0.355, P<0.001; r_s=-0.180, P=0.034), and was not obviously correlated with the ratio of horizontal to vertical time (r=0.038, P=0.656).

The DEM test scores of Chinese children with developmental dyslexia are higher than those of normal children, and there is no difference between different genders.The lower the scores of vocabulary size test, the higher the scores of DEM test.

Dyslexia; Child; Language test; Vocabulary size; Developmental eye movement test; Detection rate; Chinese