There was no immediate improvement in mobility performance of visually impaired adults after orientation and mobility training. Familiarity with the route may play an important role in measured improvement of mobility performance after orientation and mobility training.
Our study suggests that: practitioners should be alert to potential mobility difficulties when the visual field is less than about 1.2 sr (70° diameter); assessment for mobility rehabilitation may be warranted when the visual field is constricted to about 0.23 to 0.63 sr (31 to 52° diameter) depending on the nature of their visual field loss and previous history (at risk); and mobility rehabilitation should be conducted before the visual field is constricted to 0.05 sr (15° diameter; critical).
Foveal detection of a Gabor patch (target) is facilitated by collinear, displaced high-contrast flankers. Polat and Sagi reported that the same phenomenon occurred in the periphery, but no data were presented [Proc. Natl. Acad. Sci. 91 (1994) 1206]. Others have found no facilitation in a limited number of conditions tested. To resolve this apparent conflict, we measured lateral facilitation in the near-periphery using a range of stimulus parameters. We found facilitation for a range of target-flanker distances for peripheral eccentricities up to 6 degrees , but the magnitude of the effect was less than found in central vision. Facilitation varied across subjects and with spatial frequency. Flanker contrast had no effect over the range evaluated (10-80%). Equal facilitation was found for two global arrangements of the stimulus pattern. Facilitation was found using a temporal, but not a spatial two-alternative forced-choice paradigm, accounting for the different results among previous studies. This finding supports previous indications of the role of attention in altering such facilitation. The value of facilitation from lateral interactions for persons with central vision impairment, who have to shift their attention to a peripheral locus constantly, needs to be examined.
Background: As vision plays a significant role in mobility performance, it is usual to refer low vision patients, particularly those who complain of mobility difficulties, for orientation and mobility (O&M) training to help them maintain safe independent travel. Our study aimed to determine whether there was a relationship between measures of vision and self‐reported mobility, and the applicability of a patient‐based mobility assessment in patients with heterogeneous causes of visual loss. Method: We assessed the high and low contrast visual acuity, visual field and scanning ability of 30 patients with low vision. A validated mobility questionnaire was used to assess the participants’ perceived visual ability for independent mobility. Results: Vision was significantly correlated with self‐reported mobility performance, however, visual field was a significant predictor accounting for 56.5 per cent of the variance. The instrument was well constructed with valid content and high reliability scores. Conclusions: Self‐reported mobility performance together with measures of vision could be used as a guide to refer patients for O&M training. The patient‐based assessment instrument was valid to measure perceived visual ability for independent mobility in patients with heterogeneous causes of visual loss.
Background: If visually impaired people had their sight fully restored, it is assumed that they would walk at their optimal speeds. Previous mobility studies have used preferred walking speed (PWS) to measure walking efficiency of visually impaired adults. Therefore, the actual speeds that visually impaired people adopt on a route can be expressed as a percentage of their preferred walking speed (PPWS). There have been two approaches used in previous studies for determining preferred walking speed. the sighted guide technique (SG), which requires a subject to walk with a sighted guide and regard the latter as a perfect mobility aid, with the subject setting the preferred (optimal) walking pace. the non‐sighted guide technique (NonSG), which requires a subject to walk alone along an unobstructed straight path for a certain distance, adopting the preferred (optimal) walking speed. There is some debate on which technique is the better. This study was conducted to determine if there is any difference between the two techniques for determining visually impaired subjects' preferred walking speeds. Methods: Fourteen visually impaired adult subjects were recruited. PWS was determined by recording the time taken for a subject to walk an unobstructed, straight 20‐metre corridor path using each technique. Results: There was no significant difference in PWS using the sighted guide and non‐guided techniques. Conclusions: Either the SG or NonSG techniques can be used to determine PWS for a heterogeneous group of visually impaired subjects.
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