C E K Chandler¹, C M Dickinson², J Sznapka¹, R A Harper¹
¹Manchester University, Ophthalmology, Manchester, United Kingdom; ²UMIST, Optometry & Neuroscience, Manchester, United Kingdom
Purpose
To validate and to estimate test-retest reliability for an orientation and mobility (O&M) course to be used as an outcome measure of low vision rehabilitation and autofocus bioptic device use in subjects with visual impairment.
Method
16 normally sighted subjects (0.00 logMAR or better) were recruited (mean ages=24 years, range 22-28). The O&M course comprised a high-density obstacle course with 10 tasks (e.g. identification of a food item on a shelf). Time, collision frequency, and accuracy for task completion were recorded. All 16 subjects completed the course without simulated impairment. 8 subjects were then assessed using 'foil' spectacles to simulate contrast/acuity loss (acuity ~0.4 logMAR). The other 8 subjects were assessed using 3mm binocular pin-hole goggles to simulate field loss to 12.5°. Subjects were re-tested for both conditions 1 week later.
Results
A three-factor repeated measures ANOVA was conducted. A significantly longer time was found when subjects had contrast/acuity impairment (mean = 13.65, F=324.11, p<0.05) than without impairment (mean = 6.54). A significantly longer time was also found when subjects had marked field impairment (mean = 15.40, F=207.67, p<0.05) than without impairment (mean = 6.94). Field impairment caused a significant increase in time taken compared with contrast/acuity simulation (F= 165.69, p<0.05). A significant order effect was not found for test-retest visits.
Conclusion
The course differentiates between performance for normally sighted individuals and those with visual impairment, and between different types of impairment. The measures appear stable over time, thereby facilitating use as an outcome in subsequent research.
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