Eye tracking dysfunction in Alzheimer-type dementia.

Performance on visual tracking tasks was measured in groups of Alzheimer-type dementia, pseudodementia of depression, and elderly normal controls. Smooth pursuit tracking errors were identified by counting the number of catch-up saccades required to compensate for failure of the smooth pursuit system. The group with Alzheimer-type dementia had significantly worse (p less than 0.0001) smooth pursuit tracking than either pseudodementia subjects or elderly normal controls. A strong correlation (r = 0.74, p less than 0.005) was found in Alzheimer patients between severity of visual tracking abnormality and severity of dementia.