[A study on visual development among preschool children].

Objective: To evaluate the visual development and prevalence of amblyopia, strabismus among preschool children.
Methods: A random sample survey was performed in 4 610 preschool children from both urban and rural, aged 3 to 6 years. Participants underwent eye examination including visual acuity, refractive status, eye position, strabismus and amblyopia.
Results: Percentage of visual acuity above 1.0 was 28.4%, 39.3%, 46.2% and 76.5% in children of 3, 4, 5 and 6-year-old group, respectively. The mean visual acuity of each group was 0.63 ± 0.19 in 3-years old, 0.69 ± 0.16 in 4-year-old, 0.71 ± 0.22 in 5-year-old, 0.79 ± 0.29 in 6-year-old. Rural children have better vision acuity compared with those from urban. Hypermetropic was frequent refractive errors. Manifeststrabismus was found in 2.21%, with exotropia being more prevalence than esotropia; detection rate of recessive strabismus was 33.52%, mainly being exophoria; Based on current diagnostic criteria, the prevalence of amblyopia were 2.93% in 6 year-old group, 4.81% in 5-year-old group, 16.21% in 4-year-old group, 33.33% in 3-year-old group.
Conclusion: Vision acuity is increasing with age in preschool population. A diagnosis standard of amblyopia suitable for each age group should be established to substitute the current one which has a high visual standard for amblyopia. Refractive error, strabismus and amblyopia are the leading causes of visual impairment among preschool-aged children, which represent the focus of prevention of blindness in preschool children.