Sensory reweighting in central visual field loss

Aging leads to vestibular deficits that contribute to older adults’ visual field dependence for perception and postural control. These age-related vestibular changes, combined with vision loss and oculomotor changes, may explain the higher fall risk and mobility issues of individuals with age-related central visual field loss (CFL). 

In a first study, we examined whether the age-related increase in visual field dependence persists despite CFL, or whether a reweighting occurs to leverage vestibular and somatosensory cues. Using a subjective visual vertical task, adapted for individuals with CFL, we tested older adults with monocular and binocular CFL and age-matched controls. We indeed observed that visual field dependence persisted in the CFL groups, despite reduced/less reliable vison. Additionally, those with binocular loss were significantly more visual field dependent than control participants, likely due to due to the spared peripheral retina. These findings are important when considerating appropriate mobility rehabilitation and aids for this population given the association between visual field dependence and fall risk. 

Indeed, those who upweight visual cues tend to be more fall-prone, in part due to changes in body coordination. Vestibular signals drive optimal head stabilization when moving. In a second study, we examined head stabilization via motion capture in individuals with CFL and controls during a functional mobility task, to assess whether vestibular input is appropriately leveraged in CFL. Results varied across individuals, with poorer vision correlating with reduced control (greater head accelerations). These findings suggest, again, issues of sensory reweighting that can be addressed via targeted training.