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Rakie Cham, Caitlin O'Connell, Mark Redfern, Ian Conner, Gadi Wollstein, Kevin C Chan; Balance and brain connectivity in glaucoma. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1944.
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Patients with glaucoma are at an increased risk of falling. Brain processes needed for the integration of sensory information relevant for balance require attention-related resources and may be altered in patients with glaucoma. The purpose of this study was to examine if glaucoma impacts the interference between attention and balance, and to determine if the findings are linked with brain connectivity alterations.
Twelve adults with glaucoma were recruited (average age 65.7±8.9 years, visual field mean deviation (VF MD) worse eye -8.9±9.5 dB, VF MD better eye -2.4±3.3 dB). Balance was assessed while standing quietly on a fixed floor and on a floor rotating in such a way that minimizes proprioception. Balance was quantified using sway velocity (increased velocity reflecting worse balance). Participants completed these tests with and without a reaction time task requiring them to push a button when they hear tones; performance was assessed using the median response time (RT) to 45 stimuli in each condition. Diffusion tensor imaging scans of the brain obtained using magnetic resonance imaging (MRI) were collected for seven participants. Brain connectivity was assessed by fractional anisotropy (FA) in the optic radiation and superior & inferior occipito-frontal fascicles. Analysis consisted of a set of linear regressions (α=0.05).
Changes in balance performance due to the addition of a reaction time task was associated with retinal nerve fiber layer (RNFL) thickness, with balance worsening with thinner RNFL (p=0.05; Fig 1a; rotating floor). The effect of standing on a rotating floor on RTs was associated with RNFL thickness, with faster RTs found in subjects with thinner RNFL (p=0.004; Fig 1b). When standing on the rotating floor, RT decreased as FA decreased in the optic radiation and superior/inferior occipito-frontal fascicles (p=0.04, p=0.01, p=0.02, respectively; Fig 2).
The results suggest that patients with more advanced glaucoma may have difficulty prioritizing balance during challenging postural conditions. Brain connectivity alterations in patients with glaucoma may be related to attentional control of standing balance.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
a) Impact of RNFL thickness on change in balance when performing a reaction time task relative to no task (rotating floor condition shown). b) Impact of RNFL thickness on change in RT when standing on a rotating floor relative to unperturbed standing.
Association between FA and RT (rotating floor).
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