Benefit of Bi-Ocular Visual Stimulation for Postural Control in Children with Strabismus

Abstract

Vision is important for postural control as is shown by the Romberg quotient (RQ): with eyes closed, postural instability increases relative to eyes open (RQ = 2). Yet while fixating at far distance, postural stability is similar with eyes open and eyes closed (RQ = 1). Postural stability can be better with both eyes viewing than one eye, but such effect is not consistent among healthy subjects. The first goal of the study is to test the RQ as a function of distance for children with convergent versus divergent strabismus. The second goal is to test whether vision from two eyes relative to vision from one eye provides better postural stability. Thirteen children with divergent strabismus and eleven with convergent strabismus participated in this study. Posturtography was done with the Techno concept device. Experiment 1, four conditions: fixation at 40 cm and at 200 cm both with eyes open and eyes covered (evaluation of RQ). Experiment 2, six conditions: fixation at 40 cm and at 200 cm, with both eyes viewing or under monocular vision (dominant and non-dominant eye). For convergent strabismus, the groups mean value of RQ was 1.3 at near and 0.94 at far distance; for divergent, it was 1.06 at near and 1.68 at far. For all children, the surface of body sway was significantly smaller under both eyes viewing than monocular viewing (either eye). Increased RQ value at near for convergent and at far for divergent strabismus is attributed to the influence of the default strabismus angle and to better use of ocular motor signals. Vision with the two eyes improves postural control for both viewing distances and for both types of strabismus. Such benefit can be due to complementary mechanisms: larger visual field, better quality of fixation and vergence angle due to the use of visual inputs from both eyes.

Postural stability and visual impairment: Assessing balance in children with strabismus and amblyopia

“…Equal and optimal visual acuity, binocular vision (stereopsis), and vergence eye movements should all contribute to postural stability. Unfortunately, the contributions of the various elements of vision to balance control are not fully confirmed [ 15 – 20 ]. There is conflicting evidence regarding the effect of monocular viewing on postural control [ 15 , 17 , 19 ].…”

“…Unfortunately, the contributions of the various elements of vision to balance control are not fully confirmed [ 15 – 20 ]. There is conflicting evidence regarding the effect of monocular viewing on postural control [ 15 , 17 , 19 ]. Previous reports showed that balance could be affected by mild visual disorders [ 21 , 22 ].…”

Visual and vestibular functioning, and age and surgery effects on postural control in healthy children with vertical strabismus

“…Legrand and colleagues reported improving effects of ocular surgery on postural control 2 months after surgery 5 and following re-alignment of the eyes with prisms and with eye surgery, 6 demonstrating that improving binocular vision determines significant postural control gain. Gaertner and colleagues 7 confirmed benefits of binocular vision on postural control in strabismic children. To the best of our knowledge, even if visual–vestibular interactions mature very early in infancy, no previous studies have investigated visual and vestibular functioning in children with strabismus.…”

Walking strategies in subjects with congenital or early onset strabismus

“…However, a binocular visual stimulation plays an important role in postural control of patients with strabismus (Gaertner et al, 2013b).…”