Normative Data for Nonstrabismic Binocular Vision Parameters in African Schoolchildren

With reported population differences in parameters of nonstrabismic binocular vision, the present study investigated and reports normative data among a sample of African children. PURPOSE: This study aimed to determine expected binocular visual function data among schoolchildren in the Central Region of Ghana. METHODS: The study used a prospective cross-sectional design and used a multistage cluster sampling approach. Eligible normal participants selected through the administration of Convergence Insufficiency Symptom Survey questionnaire (score <16) and preliminary vision screening underwent comprehensive binocular vision testing. Only data for participants who expressed no difficulty with the specific procedures were analyzed. RESULTS: A total of 1261 normal participants (11 to 17 years [mean, 14.75 ± 1.530 years]) were selected for comprehensive binocular vision testing in the normative data study. The means with ±1 standard deviation for normative data for the nonstrabismic binocular vision parameters include the following: accommodative target near point of convergence (NPC) break (6.10 ± 1.67 cm), NPC recovery (8.17 ± 1.67 cm), fixation light with red-green anaglyph (RG NPC) break (8.51 ± 2.43 cm), RG NPC recovery (10.95 ± 2.60 cm), cover test distance phoria (0.12 ± 0.79 exophoria), cover test near phoria (2.1 ± 2.3 exophoria), modified Thorington test near phoria (1.9 ± 2.5 exophoria), negative relative accommodation (+2.54 ± 0.75 D), positive relative accommodation (−2.58 ± 0.81 D), and the accommodative convergence over accommodation ratio (2.80 ± 1.07:1). Age (in years)-predicted normal linear regression equations for NPC break (5.13 + 0.07 × age), RG NPC break (10.00 − 0.10 × age), RG NPC recovery (12.83 − 0.13 × age), positive relative accommodation (2.05 + 0.04 × age), and the gradient accommodative convergence over accommodation ratio (3.97 − 0.08 × age) serve as a guide. CONCLUSIONS: The study provides expected data that optometrists may use with similar aged Black African populations.