EFFECTS OF REFRACTIVE ERROR ON DETECTION ACUITY AND RESOLUTION ACUITYIN PERIPHERAL-VISION

Purpose. To evaluate the effect of refractive error on detection acuit y and resolution acuity in peripheral vision. Methods. Detection acuit y, defined as the highest spatial frequency for which luminance gratin gs can be discriminated from a uniform field, and resolution acuity, d efined as the highest spatial frequency for which spatial patterns are perceived veridically, was determined for vertical and horizontal gra tings located at 20 degrees, 30 degrees, and 40 degrees of eccentricit y. Resolution was also measured for tumbling-E discrimination at these locations. Refractive state of the eye for test targets was manipulat ed by introducing an ophthalmic trial lens into the line of sight for the stimulus while holding accommodative state fixed. Results. Detecti on acuity in the periphery varied significantly with the amount of opt ical defocus, whereas acuity for grating resolution or letter discrimi nation was unaffected by defocus over a large range (up to 6 D). These results are consistent with the working hypothesis that detection acu ity in the periphery is limited by contrast insufficiency under normal viewing conditions, but resolution is limited by ambiguity because of neural undersampling. Conclusions. The large depth of focus for resol ution acuity measured for peripheral vision indicates that spatial res olution is likely to remain sampling-limited even when peripheral refr active errors are not fully corrected, thus relaxing the methodologic requirements for obtaining noninvasive estimates of neural sampling de nsity of the living eye in a clinical setting.