Material and Method: Sixty-three students identified as having a visual acuity of poorer than 20/40 screening by a research assistant underwent a complete assessment including a visual acuity test, orthoptic examination, refraction, and cover tests were enrolled in the present study. Corneal light reflex photographs were obtained using a compact camera. The subject was photographed head-on, the photos were taken at a distance of one (near) and six (distance) meters, and each image was measured twice using the Adobe Photoshop software program. The CCLRR was the ratio of the summated bilateral distances between the central corneal light reflex (CCLR) and nasal limbus to the summated bilateral corneal diameters. Normal range of CCLRR was estimated based on a hypothetical normal range defined by mean + 1.58 standard deviations.

Results: The present study included 63 students with a best correct visual acuity of better than 20/40 and a mean age of 9.18 (SD 1.72) years, comprising 36 males (57.1%) and 27 females (42.9%). The alternate prism cover test (APCT) at near/at distance, a certified diagnosis, revealed 29 (46.05%)/54 (85.7%) orthophoria, 29 (46.05%)/6 (9.5%) exophoria, 4 (6.3%)/1 (1.6%) intermittent exotroria, 0 (0%)/2 (3.2%) exotropia, and 1 (1.5%)/0 (0%) esotropia. The mean of stereopsis was 59.05 + 50.47 (range of 40 to 400) seconds of arc. The normal range of CCLRR at near/at distance was 0.446 to 0.484/0.421 to 0.482, while the indeterminate groups at near were 0.435 to 0.445, and 0.485 to 0.495, and at distance 0.403 to 0.420 and 0.483 to 0.500. The cases that had lower or higher ratios should be considered as suspected strabismus.

Conclusion: Normal range of CCLRR in Thai children is established.

Keywords: Central corneal light reflex, Screening, Children