The effect of orientation and mobility training on vision and mobility performance in visually impaired adults

A number of studies have investigated various visual functions of visually impaired subjects and how their visual functions relate to the subjects' ability to travel in their environment. Most studies have shown that visual field and contrast sensitivity are the most important visual factors in determining how well visually impaired subjects travel in their environment. From the outcome of the studies, some aspects of vision are known to play important roles in mobility performance of visually impaired subjects. However, in all these studies, researchers have used visually impaired subjects with differing degrees of mobility skills. The mobility performance measured in previous studies may differ among subjects depending on the level of their mobility skills rather than differences in visual function. One of the main factors which may affect subjects' mobility skills is whether or not they have had orientation and mobility (O&M) training. Anecdotal evidence reported by mobility instructors and visually impaired clients suggests that O&M instruction does improve independent travel skills. In view of the limitations of previous studies, the current study attempted to determine the effect of O&M training on vision and mobility performance of visually impaired adults. Vision and mobility performance of a group of visually impaired subjects were examined before and after O&M training. As the same group of subjects were investigated, the effects of other factors which influenced their mobility skills may be controlled. Based on the best predictors of mobility performance, vision criteria for O&M training referral were recommended. Methods. Vision and mobility performance of 2 groups of visually impaired subjects with various ocular diseases were assessed: the experimental group T who were referred and received mobility training and the control group NT with no previous mobility training and were not referred for training. Visual performances were measured binocularly as high and low contrast visual acuities, letter and edge contrast sensitivities and kinetic visual fields. The subjects' mobility performance was measured on an indoor mobility course: 1) walking efficiency was assessed as percentage preferred walking speed (PPWS) 2) mobility incidents were assessed as errors made during travel on the course. Vision and mobility performances were measured before training and approximately 4 weeks after completion of training for group T whilst group NT was assessed at two visits with a similar time period between visits as for group T. A questionnaire was administered to each group at both visits and six months after the second visit. Results. Walking efficiency of group T improved with short-term practice immediately following O&M training but there was no improvement due to long-term practice or training. On the other hand, there was no improvement in error score either due to practice or training immediately after O&M training. Error score of all subjects improved as a result of prior experience. Self-reported mobility performance did not improve immediately after O&M training but improved six months after training. Stepwise multiple regression analysis showed that visual field was a significant predictor before and after O&M training; it accounted for 20.4 percent and 31.2 percent of the variance in PPWS and error score respectively before training whilst accounting for 20.0 percent and 16.8 percent of the variance in PPWS and error score respectively after training. Stepwise multiple regression analysis of groups T and NT together showed that LCV A and inferior remaining visual field were best predictors of PPWS and error score respectively; PPWS began to deteriorate when LCVA was 6/150 or worse whilst error score began to decline when inferior remaining visual field was 45 degrees radius or less (between the field extent of 225 and 315 degrees). Conclusions. Mobility performance of visually impaired adults may be improved following O&M training, however, further research needs to be conducted to ascertain the level of improvement in performance over time. Visual field was shown to play a significant role in mobility performance of visually impaired adults regardless whether or not they have had O&M training, however, further research is required to ascertain the role of LCV A in walking efficiency. Tentative criteria for O&M training referral were recommended: LCVA 61150 or worse and/or inferior remaining binocular visual field of 45 degrees or less using the target IV 4 E.\ud \ud However, further research is needed to ascertain if these criteria are applicable to other visually impaired groups