Asymptomatic physiologic hyperdeviation in peripheral gaze.

Asymptomatic hyperdeviation (HD) in peripheral gaze may be caused by muscle paresis, restrictive orbital diseases, cranial neuropathy, or skew deviation. The authors suspected that this finding was often physiologic and therefore examined 61 normal subjects with the Maddox rod. Forty-seven of 61 patients (77%) showed an HD of 2 prism diopters (PD) or greater in any field of gaze; 22 of these 47 patients (47%) showed an isolated left HD in right upgaze and right HD in left upgaze; an additional 15 of the 47 patients (32%) had either a right HD in left upgaze or a left HD in right upgaze. In only one patient was a vertical phoria evident in primary gaze. Ninety-four percent noted vertical diplopia where the deviation was found. In 40 of 47 patients (85%), a "V" pattern of less than 15 PD was detected. No HD in primary gaze on head tilt was elicited in those tested. Awareness of this highly prevalent physiologic HD, which follows the pattern of primary overaction of the inferior oblique muscle, may ward off erroneous neurologic diagnoses.