Four Shades of Gray: Understanding the Effect of Visual Contrast on Step Edges to Improve Safety

Abstract

Stair falls during descent are a dangerous and costly occurrence. Contrasting tread edge highlighters have been shown to improve measures of stair safety, however the necessary contrast magnitude of these aids has not been investigated. Data from thirteen older adults (age; 67.7 ± 5.5 years) were analyzed as individuals completed stair descent trials under normal and low lighting conditions, blurred and normal vision, and four different contrast levels between the tread edge highlighter and the staircase. Cadence, foot-to-step clearance, and degree of foot overhang were determined for all conditions, and were significantly affected by contrast level. Blurred vision was observed to be a greater factor influencing biomechanical measures of fall risk than low ambient lighting. Results suggest higher contrast highlighters improve measures of safety, even more so during simulated vision impairment, and that at least 50% contrast difference may be necessary to provide adequate visual information for safer stair ambulation.