The effect of grating orientation on resolution acuity in patients with nystagmus.

The acuity card procedure is an effective method for the assessment of grating acuity in preverbal and nonverbal patients. However, the effect of nystagmus on this acuity assessment has not been well-described. We studied the effect of grating orientation on the measurement of resolution acuity in a group of nystagmus patients, a group of patients with albinism and nystagmus, and a normal control group. The resolution acuity was significantly (P < or = .01) better with horizontal grating orientation in both the nystagmus and the albino groups, but grating orientation did not affect resolution acuity in the control group. This study suggests that grating orientation must be taken into account when using the acuity card procedure in patients with nystagmus.