Material and Method: A cross-sectional analytical study was conducted in four provinces representing four geographic regions of Thailand. Three hundred fifty four students who had visual acuity of less than 20/40, assessed by their school teachers and completed an eye examination with orthoptic measurement were included. Two digital images were taken, using a flash, with each student looking at a target at distances of 1 m and 6 m. The central corneal light reflex ratio (CCLRR) from the digital image was automatically calculated from an image analysis algorithm for strabismus screening. The study compared the computer results from the digital images with the results of the strabismus examinations.

Results: Pre-test probability for strabismus in preschool and school children post visual screening was about 15%. The likelihood ratio for high-risk, intermediate-risk, and low-risk from the photographs were 17.44, 1.51, and 0.76, respectively. Post-test probability for high-risk, intermediate-risk, and low-risk from the photographs were 75%, 21%, and 12%, respectively.

Conclusion: It is possible to develop a computer system for strabismus screening. The likelihood ratio for high-risk from the photographs was 17.44.

Keywords: Strabismus, Screening, Computer, Probability, Likelihood ratio