Gender differences and the risk of falls in individuals with profound vision loss

Individuals with visual impairments must place a greater demand on somatosensory (the ability of the somatic senses to detect body position and maintain an upright and stable stance) and vestibular (the ability of the sensory system of the inner ear to detect rotation and acceleration to maintain a stable and up-right stance) information to establish patterns of movement when positions in space are compromised by the lack of vision or by minimal vision (Horvat, Ray, Ramsey, Miszko, Keeney, & Blasch, 2003) Previous data from the University of Texas Arlington Postural Control Laboratory indicated that vision loss results in reduced postural control (Ray, Horvat, Croce, Mason, & Wolf, 2008). The movement of individuals with visual impairments depends on the use of sensory information other than vision to initiate changes in the center of gravity and base of support prior to a movement. Although most individuals require vision to maintain postural stability, others can maintain an upright position accurately without visual information (Williams, 1983). However, balance with vision is more efficient and skillful than balance without vision, especially in changing conditions (Williams, 1983). Common problems that are associated with visual impairments are the use of other sensory and vestibular information to establish and connect movement patterns and to adjust to positions in space (Spirduso, 1995). Standing balance is diminished because the loss of vision affects the vestibular system via the lack of visual feedback (Judge, Davis, & Ounpuu, 1996; Maeda, Nakamura, Otomo, Higuchi, & Motohashi, 1998). Adults with visual impairments experience a loss of balance and mobility, which presents a barrier to independence and is associated with the fear of falling (Crews & Campbell, 2001; Rosen, 1997; Skaggs & Hopper, 1996). The purpose of the study reported here was to determine the extent to which visual status, age, gender, body mass index (BMI), and the strength of quadriceps and hamstrings contribute to compromised postural control in adults with visual impairments. Establishing these relationships is an important prerequisite to identifying at-risk subpopulations and the future development of evidence-based therapeutic prescriptions that are aimed at maintaining or improving postural stability in these adults. METHODS Participants Sixty-five adults (aged 20-65) were recruited from the Dallas-Fort Worth chapters of the American Foundation for the Blind, National Federation of the Blind, and Lighthouse for the Blind of Fort Worth. The participants were divided into three categories (low vision, medium vision, and sighted) using the classification system of the International Blind Sports Association (2008). Participants in the low vision category had up to light perception, but an inability to see shapes, consistent with the partial sight permitted in the B1 sports classification of athletes who are blind. Participants in the medium vision category were able to recognize hand movements up to and including 2/60 (20/600) acuity, or a visual field limited to less than 5 degrees. Participants in the sighted category were those with typical age-related vision loss, a corrected vision that exceeded 20/32, and no visual field loss. These three levels represent a functionally relevant transformation of LogMAR (logarithm of the minimum angle of resolution) acuities and visual fields. Height and weight were collected from all the participants to calculate their BMIs. Visual classifications, sample sizes, BMIs, determinants, and demographic characteristics are presented in Table 1. The institutional review board at the Dallas VA Medical Center approved this study, and informed consent was obtained from the participants. Measure of postural stability The Sensory Organization Test (SOT) of the NeuroCom Equitest System (NeuroCom International, Clackamas, Oregon) provides information on the use of sensory input or a combination of inputs to maintain postural stability. …