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A. Vale, J. G. Buckley, A. Scally, D. B. Elliott; Effect of Monocular Blur on Adaptive Gait. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1574.
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Monocular blur may cause a reduction in contrast sensitivity by binocular inhibition and has been shown to increase stereoacuity thresholds more than binocular blur of the same magnitude. When negotiating obstacles/steps under conditions of binocular blur subjects adopt a strategy of increasing toe clearance to reduce the risk of tripping, but as yet no studies have investigated if monocular blur will lead to a similar adaptation. The present study determined how toe clearance and stepping kinematics was affected by monocular blur or occlusion.
14 healthy subjects (age 25.8±5.64) with normal vision walked along the laboratory onto a raised surface. Trials were performed with optimal refractive correction, 2 dioptre blur over the dominant or non-dominant eye or the dominant eye occluded. Foot placement and limb kinematics were analyzed via 3D motion analysis.
Stereopsis was reduced to 257secs of arc (dominant eye blurred) and 153 secs of arc (non-dominant eye blurred). Analysis shows an 18% (p<0.001) increase in vertical toe clearance when the dominant eye is blurred but only a 10% increase (p<0.001) when the non-dominant eye was blurred. The trail (support) foot was placed further from the step (p<0.001) and knee and hip flexure increased when each eye was blurred or the dominant eye occluded.
We conclude that a relatively small amount of monocular blur (which leads to a reduction in stereopsis) can cause uncertainty in locating the step edge and increase vertical toe clearance to increase margins of safety. Blur in front of the dominant eye had a greater effect on step adaptations to blur in front of the non-dominant eye.
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