Binocular visual acuity interaction in children: summation and inhibition

To compare binocular visual acuity with the monocular visual acuity of the better eye and investigate the factors contributing to binocular interaction.

Retrospective observational study.

We enrolled 332 children. They were divided into 3 groups according to binocular interaction: group A (binocular equivalency), group B (binocular summation), and group C (binocular inhibition).

Monocular visual acuity, binocular visual acuity, and stereoacuity were evaluated. The main outcome measures were the prevalence rates of binocular interaction and factors associated with binocular interaction, including monocular visual acuity of the better eye, interocular difference of monocular visual acuity, and stereopsis.

Of 332 children, binocular summation and equivalency were noted in 218 (65.7%) and 95 (28.6%), respectively, and binocular inhibition in 19 (5.7%). The binocular visual acuity and monocular visual acuity of the better eye in group B were better than those in groups A and C, respectively (p = 0.000). There was a significant correlation between monocular visual acuity of the better eye and binocular visual acuity in groups B and C (r = 0.884, p = 0.000; r = 0.797, p = 0.000, respectively). The interocular difference of monocular visual acuity in group B (0.05 ± 0.07) was smaller than that in group C (0.13 ± 0.06) (p = 0.000). The proportion of children with good stereopsis was 74.3% in group B but only 31.6% in group C (p = 0.001).

About 66% of 332 patients had better binocular visual acuity than monocular visual acuity of the better eye. Our results suggest that the monocular visual acuity of the better eye, interocular difference of monocular visual acuity, and stereopsis affect binocular interaction.