The Normal Range of Central Corneal Light Reflex Ratio in Thai Children
Supaporn Tengtrisorn MD*
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand
Objective : To determine the range of central corneal light reflex ratio (CCLRR) in Thai children.
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
