Visual Midline Shift Syndrome (VMSS)
What is visual midline shift syndrome?
Some dizzy patients have problems perceiving their position in space. This can make them think their body midline has shifted to one side or the other. It is very difficult to coordinate your movements when you think everything has moved over to one side.
What causes visual midline shift syndrome?
Visual midline shift syndrome is caused by a mismatch between visual and spatial information processed by the brain. It often appears in patients who’ve had a stroke and can occur in up to 50% of patients with concussion (mild traumatic brain injury). If left untreated, patients with VMSS will have balance problems and postural dysfunction.
Diagnosis of visual midline shift syndrome
A regular eye exam takes about 20 to 30 minutes to determine if you need a pair of glasses. Extensive functional vision tests by a developmental optometrist can detect VMS and other functional vision issues.
Treatment of visual midline shift syndrome
VMSS is easy for a developmental optometrist to correct with the use of yoked prism and/or therapy. Yoked prisms are a pair of bilateral prisms that are “yoked” (oriented with the base in the same direction).
Their effect is basically to shift space. For example, right-yoked prism pushes everything you see over to the left. Yoked prism can be added to shift space either left or right, or up or down.
Johal S. Balance and dizziness: the visual connection. 2016. Talk presented to Balance & Dizziness Canada.