|dc.description.abstract||Falls among older adults is a serious problem facing our aging population. It is estimated that one in every three older adults aged 70+ fall every year; some of these experience multiple falls. Thirty five percent of fallers aged 65 - 70 years experience severe injuries, and this rises to 76% in the 80+ age group. Falls can cause deterioration of health, loss of independence, or even death. The first purpose of this thesis (Experiment 1) was to examine the possible link between balance, mobility, fear of falling, and aspects of vision including binocular vision (BV) status and visual attention, measured with a useful field of view test (UFV) and the Attended Field of View (AFOV). In this cross section study I was interested in measures of vision, which have been less studied or not been considered before, specifically tests of BV and visual attention. These were chosen, as previous research had shown that BV disorders are very common in older adults, and that there is an association between a number of functional tasks and visual attention. Associations with balance and mobility would be a significant finding because BV disorders are often treatable and visual attention is trainable.
Balance and mobility were assessed using the One Legged Stance test (OLST), the 5 Meter Walk test (5MWT) and the Sit to Stand test (STST). Fear of falling was measured with the Falls Efficacy Scale-International (FES-I). Visual measures included distance, intermediate and near visual acuity (VA), contrast sensitivity, stereoacuity, BV measurements, UFV and AFOV. Seventy-two adults aged 70 and older took part in the study (mean age 80.3 ± 5.9 years). The results showed that abnormal BV, poor intermediate VA and errors on the UFV were all significant predictors of reduced performance in mobility and balance. Univariate regression showed that reduced performance on the OLST and the STST was significantly correlated with abnormal BV and intermediate VA. The 5MWT and the FES-I were also predicted by poor intermediate VA. In addition, the OLST, STST and the 5MWT were all associated with the UFV errors. Multiple regression models included the following: OLST performance was related to BV and eye movement disorders, stereoacuity and UFV errors, STST was related to intermediate VA and 5MWT was related to distance VA.
The association between balance and visual attention led me to hypothesize that training visual attention may improve balance and thereby reduce falls. Falls prevention programs typically include vision, exercise, environment modification, education intervention or a combination of these interventions grouped together. The most effective programs may be those that have a multifactorial approach. However, the impact of visual attention training aimed at improving balance and/or mobility has not yet been studied. Therefore, the second purpose of this thesis (Experiment 2) was to investigation of whether visual attention training can improve balance and/or mobility in older adults, with the goal that this may transfer to reducing falls.
Experiment 2 was a randomized controlled trial (RCT) in which 15 participants were randomly assigned to a visual attention training group and 15 to a control group. Visual attention training was undertaken with versions of a selective attention useful field of view test (UFV) and attended field of view (AFOV) test. The training sessions were 45 minutes duration, undertaken twice a week for three weeks. The outcome measures were sway using a force plate platform (AMTI AccuGAIT; 200 Hz), the mini Balance Evaluation Systems Test (mini-BESTest), the One Legged Stance test (OLST), the 5 Meter Walk test (5MWT), the Sit to Stand test (STST), the Timed Up and Go test without (TUG) and with a concurrent cognitive task (TUGco). It was found that visual attention significantly improved after training (p< 0.01). However, a mixed ANOVA (2x groups, 2x visits, 5x trials) showed no main effect of visit or group or any interaction for any of the force plate platform parameters; medial lateral (ML) or anterior posterior (AP) center of pressure (CoP) standard deviation, ML and AP CoP maximum sway, ML and AP CoP range of sway and the cumulative path length for sway (p>0.05 in all cases) in eyes open and eyes closed conditions. A mixed ANOVA (2x group, 2x visits) of the changes over time for the other balance and mobility assessment tools also showed no improvement after the visual attention training (Mini-BESTest, p=0.25: 5MWT, p=0.28: OLST, p=0.31: STST, p=0.029: TUG, p=0.08: TUGco, p=0.21).
To conclude, a variety of measures of visual function were shown to be related to poor performance in balance and mobility tasks. Poor BV, distance and intermediate VA and visual attention were among these measures. It is important that eye care practitioners who work with older adults be aware of these associations, question older adults about a history of falls or walking and balance problems, and ensure that the vision of older people is optimally managed. Although visual attention itself was improved by the training, there was no improvement in either mobility or balance and no difference between the intervention and the control groups post visual attention training. It was concluded that UFV and AFOV visual attention training alone is not effective to improve balance and mobility; a training program that includes movement and visual attention may be needed to obtain improvement in balance and mobility. Since a substantial portion of the older adult population fall every year the results of this study are important as it supports the notion that a multi-component approach is still the recommended route to reduce the risk of falls.||en