Objective: To evaluate the prevalence of visual impairment of children aged four to six years in Khon Kaen City Municipality,
Thailand.
Material and Method: The visual acuity test was performed on 1,286 children in kindergarten schools located in Khon Kaen
Municipality. The first test of visual acuity was done by trained teachers and the second test by the pediatric ophthalmologist.
The prevalence of visual impairment of both tests was recorded including sensitivity, specificity, likelihood ratio, and predictive
value of the test by teachers. The causes of visual impairment were also recorded.
Results: There were 39 children with visual impairment from the test by the teacher and 12 children from the test by the
ophthalmologist. Myopia is the single cause of visual impairment. Mean spherical equivalence is 1.375 diopters (SD = 0.53). Median spherical equivalence is 1.375 diopters (minimum = 0.5, maximum =4). The detection of visual impairment by
trained teachers had a sensitivity of 1.00 (95% CI 0.76-1.00), specificity of 0.98 (95% CI 0.97-0.99), likelihood ratio for a
positive test 44.58 (95% CI 30.32-65.54), likelihood ratio for a negative test 0.04 (95% CI 0.003-0.60), positive predictive
value of 0.31 (95% CI 0.19-0.47), and negative predictive value of 1.00 (95% CI 0.99-1.00).
Conclusion: The prevalence of visual impairment among children aged four to six year old is 0.9%. Trained teachers can be examiners for screening purpose.

Keywords: Preschool visual screening, Visual impairment, Amblyopia, Ambyopia screening, Prevalence of visual impairment, Children