Impact of Visual Functions on Balance Performance in Students with Intellectual Disabilities

Allen M Y Cheong, BSc (Optom), PhD, FAAO

Abstract

Purpose

Students with intellectual disabilities (ID) are at higher risk of visual impairment because of higher prevalence of visual disorders. Recent studies have revealed poorer balance function in students with ID. However, it is unclear whether compromised vision further impairs their balance performance. In this study, we aimed to investigate the impact of visual functions on dynamic and static balance performance.

Methods

Ninety students with ID who were currently attending schools for students with special educational needs aged from 5 to 18 years old were recruited. Distance visual acuity (VA) for each eye was measured using Lea Symbols/ Grading Test or Cardiff Vision Test. Based on the acuity of the better-seeing eye, subjects were classified into normal vision (NV) or visually-impaired (VI, VA >0.48 logMAR) group. Dynamic balance function was measured by Timed-Up-and-Go test (TUG), where subjects were asked to 1) rise from a chair (positioned 3 m from a wall), 2) walk 3 m, 3) turn around, and 4) return to the chair and sit down. Static balance function was measured by instructing the subject to maintain an upright standing position as steady as possible on a force platform (AMTI BP400600) for 20 second. Postural sway in terms of total path length (cm) was measured at 4 non-randomized testing conditions, including 2 standing conditions (legs-together vs. tandem standing) and 2 visual-input conditions (fixate at a target vs. eyes-close). All balance measures were repeated for 3 times.

Results

Balance data for 45 subjects (18 VI and 27 NV) who had completed all measures were analysed using generalized estimating equations. Dynamic balance function in the VI group was slightly worse than the NV group (VI 11.5 vs. NV 11.1 sec, p=0.03). In contrast, postural sway in terms of path length in the VI group was significantly shorter than the NV (VI 68.1 vs. NV 82.8 cm, p=0.048). Combining two groups of subjects, the effects of standing and visual input played a significant role on the static balance, with significantly larger postural sway found in the tandem standing (p<0.001) and deprived visual input (p=0.01). Significant interaction effect of vision, standing condition and visual input illustrated that deprived visual information significantly interrupted the postural control in the NV group (p<0.001), but not in the VI group (p=0.15).

Conclusion

The students with NV performed better in the temporal domain in dynamic balance function. On the contrary, students with VI did not show further impairment under alternation of visual conditions. They may rely more on their somatosensory and/or vestibular inputs instead of vision to maintain their postural control. Further study on examining the effectiveness of multi-sensory training aimed at improving functions of these two sensory systems on balance function is needed.

Details

Year: 2019

Program Number: 195497

Resource Type: Scientific Presentation: Paper first choice, Poster second

Author Affiliation: The Hong Kong Polytechnic University

Co-Authors: Ho Yin Wong; Kai Yip Choi; Hoi Nga Cheung; Jung-Kai Tseng; Ching-Chung Chen; Chieh-Lin Wu; Helen Eng; George Woo

Co-Author Affiliation: n/a

Room: WE2