The authors present the findings of a prospective cohort study. Three hundred and five stroke survivors were recruited consecutively. The following exclusion criteria were applied; aphasia, cognitive impairment, visual inattention, ocular motor nerve palsy and neuromuscular disease. Fifty age-matched controls were also recruited. The testing procedure involved six steps; slow binocular vergence, fast binocular vergence, slow monocular vergence right and left eye and fast monocular vergence right and left eye. For all steps each eye was assessed separately on a three-point grading scale. Stroke survivors exhibited deficits in all steps of the testing procedure compared on the age-matched controls. Age was added as a covariate due to the apparent effect of increasing age on vergence dysfunction. Parietal lobe lesions were found to have an association with deficits on monocular slow and fast vergence. Two associations with the side of the lesion were reported. Right-sided lesions were associated with deficits of fast monocular vergence of the right eye and occipital lobe lesions resulting in homonymous hemianopia were associated with deficits of fast vergence of the ipsilesional eye. Participants with small vessel white matter disease were reported to have deficits with fast binocular vergence. The authors hypothesis from their findings that slow and fast vergence systems are anatomically separated. Some limitations are acknowledged in reference to assessment method and make-up of the sample. The authors conclude the vergence deficits have limited localising value. Further research is required to enable conclusions to be made with regard to midbrain lesions.
Assessment of slow and fast vergence in stroke survivors
Reviewed by Lauren Hepworth
Bedside assessment of vergence in stroke patients.
CONTRIBUTOR
Lauren R Hepworth
University of Liverpool; Honorary Stroke Specialist Clinical Orthoptist, Northern Care Alliance NHS Foundation Trust; St Helen’s and Knowsley NHS Foundation Trust, UK.
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