Impaired vertical phoria adaptation in patients with cerebellar dysfunction.
OBJECTIVE
To determine whether phoria adaptation to a vertical prism disparity is altered in patients with cerebellar dysfunction.


METHODS
With a computer-aided haploscope, adaptive responses of fusion-free eye position to a 10- or 30-minute period was measured in subjects wearing a 3-prism diopter vertical prism over one eye. Thirteen patients with well-documented cerebellar diseases who did not have manifest ocular misalignment or limited versional eye movement and age-matched healthy subjects participated.


RESULTS
The mean +/- SD percentage of vertical phoria adaptation was 13% +/- 22% and 20% +/- 16% for the 10- and 30-minute adaptations, respectively. These levels were significantly smaller than the respective ones in the age-matched control group (P < 0.001, repeated measures MANOVA). Seven (54%) of 13 patients, including two with genetically confirmed pure cerebellar lesions (spinocerebellar ataxia type 6), showed markedly reduced responses to both the 10- and 30-minute adaptations. In all three patients with acute cerebellar ataxia, the adaptive response was improved at the same time as remission of cerebellum-associated neurologic deficits.


CONCLUSIONS
Phoria adaptation to vertical binocular disparity is frequently impaired in patients with cerebellar dysfunction. These results bolster the hypothesis that phoria adaptation is a cerebellar-dependent response.
Kono
Reika
R
Department of Ophthalmology, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700-8558, Japan.
Hasebe
Satoshi
S
Ohtsuki
Hiroshi
H
Kashihara
Kennichi
K
Shiro
Yoshihiko
Y
D000221:Adaptation, Ocular / Q000502:physiology*; D000328:Adult; D000368:Aged; D002526:Cerebellar Diseases / Q000175:diagnosis / Q000503:physiopathology*; D005133:Eye Movements; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013285:Strabismus / Q000503:physiopathology*; D015357:Vision Disparity / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology