Subjective refraction of the peripheral field using contrast detection acuity.
BACKGROUND: Although peripheral resolution acuity is relatively unaffected by uncorrected refractive error, recent investigations of peripheral vision indicate that contrast detection is optically limited. It should be possible, therefore, to perform a subjective refraction in the peripheral visual field using a contrast detection task. METHODS: For a range of trial lenses, contrast detection acuities for vertical and horizontal gratings were measured with a two-interval forced-choice paradigm. Lens powers that maximized detection acuity were taken as the subjective refraction estimates. These powers were compared with objective refractions determined with retinoscopy and autorefractometry. RESULTS: Contrast detection acuity varied significantly with lens power at all retinal locations tested. Defocusing by one diopter from the optimum lens power reduced detection acuity by about a factor of two at 20 degrees eccentricity, and slightly less in the far periphery. Objective retinoscopy and autorefractometry agreed with subjective measurements for most conditions tested. CONCLUSIONS: Contrast detection acuity in the peripheral visual field varies with refractive blur, demonstrating the feasibility of performing subjective refraction in the periphery for a contrast detection task. Results suggest that visual fields measured with standard perimetry, which is based on contrast detection, may be affected by uncorrected peripheral refractive errors.