Computer-assisted eye examination. II. Visual evoked response meridional refractometry.

ABSTRACT A visual evoked response (VER) or visual evoked potential (VEP) method was studied in order to test its feasibility for objective refraction. An alternating bar grating generated the VER which would directly include the measurement of astigmastism. It was discovered that latency as well as amplitude of the evoked response were affected by the image clarity. Sensitivity to focus was estimated to be ± 1 diopter with the amplitude criterion. The latency criterion appeared to be promising for quantitative analysis of blur. Comparison of our results were made with those of others, and differences discussed. It appears that the VER is not as sensitive to optical degradation of bar gratings as to checkerboards. Suggestions are made for improvement of the methods in order to obtain better sensitivity to focus changes.