Grating and recognition acuities of young amblyopes.

The visual acuities of 36 young amblyopes were determined by (a) conventional recognition tests (near and distance) and (b) an adapted grating acuity card procedure. Considerable agreement between the estimates of acuity obtained with each method was demonstrated, which was generally less than, or equal to, the mean difference between adjacent Snellen lines (4.5 c deg-1). Estimates of grating acuity obtained with vertical gratings did not differ significantly from those obtained with horizontal gratings. There was no difference between the subjects' ability to detect the grating (acuity) and accurately to discriminate target orientation (horizontal or vertical). The results of the experiment are discussed in relation to previous findings of a discrepancy between grating and recognition acuities in amblyopia, and the clinical use of the acuity card procedure.