HEAD TURN IN 1-EYED AND NORMALLY SIGHTED INDIVIDUALS DURING MONOCULARVIEWING

Objective: To determine the incidence and magnitude of head turn in pe rsons unilaterally enucleated at an early age and in normally sighted persons patched monocularly. Setting: The Hospital for Sick Children, Toronto, Ontario. Participants: Fifty-two unilaterally enucleated chil dren and adults without nystagmus (median age, 10 years) who were enuc leated at an early age (median age, 18 months) due to retinoblastoma a nd 28 normally sighted children and adults. Methods: Enucleated subjec ts were videotaped while walking 15 m toward a camera under 2 conditio ns: (1) fixation relaxed (just looking at the camera) and (2) fixation forced (trying to identify a small fixation target on the camera). Co ntrol subjects were tested in the fixation forced condition only. Head turn incidence and magnitude were independently rated. Three categori es of head turn were used: ''obvious'' (> 10 degrees), ''small'' (5 de grees-10 degrees), and ''no'' (0 degrees-4 degrees). Results: In the f ixation relaxed condition, 22 (42%) of 52 enucleated subjects exhibite d head turn; when fixation was forced, the incidence increased to 25 ( 58%) of 43 subjects. Head turn was virtually always in the direction o f the missing eye. Incidence and magnitude of head turn were unrelated to age at enucleation or number of years since enucleation. In the co ntrol group, there was no consistent finding of head turn across subje cts when 1 eye was patched. Conclusions: One-eyed children frequently exhibit head turn unrelated to the presence of nystagmus. The directio n of the head turn is ''adaptive'' because occlusion by the nose in th e lower contralateral field is reduced.