Validity of vision screening tests by teachers among school children in Mashhad, Iran

To determine the sensitivity and specificity of vision screening in Iranian schools where teachers have provided screening services for over 10 years.

In a cross-sectional study, using random cluster sampling, 1163 school children were selected from 14 clusters. Data of vision tests performed by teachers were derived from 847 student records and compared with data obtained by optometrists. Measurement of the uncorrected visual acuity was done using the E chart by both the teachers and the optometrists. Examinations performed by optometrists were regarded as gold standard in this study and the sensitivity and specificity of the examinations performed by teachers were evaluated against them. Uncorrected visual acuity worse than 20/25 in the better eye was considered as the cut-off point for students' visual impairment.

The sensitivity and specificity of the screening tests performed by the teachers were 37.5% and 92.0%, respectively. The positive and negative predictive values were 25.0% and 95.4%, respectively. There was no significant difference in the validity of the vision test between males and females (P = 0.093 for sensitivity and P = 0.052 for specificity).

Our findings showed that teachers missed a significant number of children with vision impairment and the examinations performed by teachers lacked the required sensitivity for case detection. The number of false negative results should be minimized through continued investment in accurate screening processes.