Emmetropia is associated with better best-corrected visual acuity (BCVA) and stereoacuity, according to research published in the Journal of the American Association for Pediatric Ophthalmology and Strabismus. The report also revealed that exophoria does not interfere with stereopsis, but esophoria and anisometropia do.
Researchers retrospectively analyzed study data from 5491 healthy individuals (75.8% men or boys; mean age, 17.6±0.9 years). Overall 2355 participants had myopia (42.9%), 640 (11.6%) had hyperopia, and the rest were emmetropic. A total of 2006 participants (36.5%) had astigmatism, with 619 having oblique astigmatism (axis between 30°-60° or 120°-150°). A total of 598 participants (10.9%) had anisometropia (interocular spherical equivalent [SE] difference of ≥1 D).
Investigators determined that emmetropia correlated with better best-corrected visual acuity while astigmatism and high hyperopia were associated with poorer best-corrected visual acuity. Among 331 participants (6%) with heterophoria greater than 8Δ, 300 (90.6%) had exophoria and 31 (9.4%) had esophoria.
Exophoria prevalence was higher among participants with myopia, but it was not associated with stereoacuity. Esophoria and anisometropia were associated with worse stereoacuity, and patients with emmetropia and no astigmatism had the best stereopsis.
“Low hyperopia, astigmatism, and anisometropia, even if corrected, mildly reduced monocular and binocular visual performance,” according to the researchers. “In contrast, myopia and exophoria did not reduce monocular or binocular performance.”
Study limitations include potential geographical bias and the strict inclusion of individuals who were healthy and young.
Armarnik S, Kozlov Y, Yahalomi T, et al. The influence of refractive state and heterophorias on visual acuity and stereoacuity in healthy young adults. J AAPOS. Published online July 18, 2022. doi:10.1016/ j.jaapos.2022.04.008