Purpose: We propose that eyelid squint can reduce the impact of several conditions known to cause eyestrain such as uncorrected refractive error, accommodative dysfunction, presbyopia, and glare. Clinicians commonly accept that squint improves visual acuity (VA) in the presence of refractive error, and even though the benefit of eyelid squint in bright light seems self-evident, data are not available to support either benefit. The purpose of this study was to measure the effect of eyelid squint on VA in the presence of refractive blur and on visual field sensitivity.