Abstract
Purpose:
To evaluate the impact of glaucoma-related vision loss on static and kinematic balance using wireless inertial sensors.
Methods:
Balance assessment was performed in 194 glaucoma patients and controls using a wireless inertial sensor system (Opal kinematic system, APDM Inc.). Sensors detected measures of total sway area (area spanned by the acceleration signal per second), RMS sway (root mean square of the acceleration signal series), 95% ellipse sway (area covering the acceleration signal with 95% probability), and jerk (time derivative of acceleration) during eyes-open standing on a foam surface to assess static balance in the absence of proprioceptive inputs. Sensors were also worn during timed up and go testing to detect trunk range of motion, angular velocity of turns, stride length, cadence (steps per minute), double-support time, and time to complete the task. Linear regression models were used to determine the association between balance parameters and glaucoma severity as determined by visual field (VF) loss while controlling for age, sex, and race.
Results:
Subjects averaged 70.6 ± 7.4 years of age with better-eye mean deviation averaging -4.6 ± 7.0 decibels. In tests of static balance with eyes open on a foam surface, worse better-eye VF loss was associated with greater total sway area (β = 0.00034 m2/s5, 95% CI = 0.00011 to 0.00057 , p = 0.004), RMS sway (β = 0.0010 m/s2, 95% CI = 0.000064 to 0.0020, p = 0.037), 95% ellipse sway area (β =0.0023 m/s4, 95% CI = -0.000042 to 0.0047, p = 0.054), and jerk (β = 0.015 m2/s5, 95% CI = 0.0033 to 0.013 , p = 0.004). In timed up and go testing, greater better-eye VF loss significantly predicted the presence of decreased stride length (β = -0.18% of stature, 95% CI = -0.32 to -0.043, p = 0.011). No statistically significant association was observed for other measures of static and kinematic balance.
Conclusions:
Adults with greater glaucoma disease severity demonstrate worse balance while standing, possibly as a result of reduced visual inputs. Adults with more severe glaucoma also exhibit decreased stride length during walking. Future work should determine which of these parameters, if any, are associated with glaucoma-related mobility deficits, i.e. falls, fear of falling, and activity restriction.