Shang K, et al. - Because strabism can lead to sustained adduction or abduction, researchers studied the effects of long-lasting unilateral horizontal strabismus on the morphology of optic disc. The study sample consisted of 70 patients (mean age was 26 ± 19 years) with unilateral constant horizontal strabismus lasting for more than 2 years. According to this observational cross-sectional study, the disc ovality index [defined as ratio of minimal-to-maximal optic disc diameter] did not vary markedly among esotropic eyes, exotropic eyes, and non-strabismic eyes in a non-highly myopic group. It indicates that a prospective backward pull of the optic nerve on the optic disc structures in adduction or abduction did not significantly influence the disc shape and vertical disc rotation.