Head turn in 1-eyed and normally sighted individuals during monocular viewing
H. C. Goltz, M. J. Steinbach and B. L. Gallie
Center for Vision Research, York University, Toronto, Ontario.
OBJECTIVE: To determine the incidence and magnitude of head turn in persons
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 children and
adults without nystagmus (median age, 10 years) who were enucleated at an
early age (median age, 18 months) due to retinoblastoma and 28 normally
sighted children and adults. METHODS: Enucleated subjects were videotaped
while walking 15 m toward a camera under 2 conditions: (1) fixation relaxed
(just looking at the camera) and (2) fixation forced (trying to identify a
small fixation target on the camera). Control subjects were tested in the
fixation forced condition only. Head turn incidence and magnitude were
independently rated. Three categories of head turn were used: "obvious"
(> 10 degrees), "small" (5 degrees-10 degrees), and "no" (0 degree-4
degrees). RESULTS: In the fixation relaxed condition, 22 (42%) of 52
enucleated subjects exhibited head turn; when fixation was forced, the
incidence increased to 25 (58%) of 43 subjects. Head turn was virtually
always in the direction of the missing eye. Incidence and magnitude of head
turn were unrelated to age at enucleation or number of years since
enucleation. In the control group, there was no consistent finding of head
turn across subjects when 1 eye was patched. CONCLUSIONS: One-eyed children
frequently exhibit head turn unrelated to the presence of nystagmus. The
direction of the head turn is "adaptive" because occlusion by the nose in
the lower contralateral field is reduced.
