Eye movement abnormalities during reading in patients with Alzheimer disease

Objective: This goal of this study was to evaluate reading ability by asses sing eye movements during reading among patients with Alzheimer disease (AD ) compared with normal elderly controls. Background: Reading is disturbed i n patients with AD. These patients may have changes in reading ability earl y in the course of their disease before clinical alexia or abnormalities ar e apparent on standard reading tasks. Method: Reading competence was evalua ted by recording eye movements during reading in 14 patients with mild to m oderate clinically probable AD and 14 age- and education-matched controls. Results: All patients with AD could recognize letters and words and could u nderstand written material of similar difficulty. Despite successful readin g comprehension among the patients with AD, their oculographs showed slowed reading and irregular eye movements. Compared with controls, the patients with AD did not differ in saccadic duration; however, they had significantl y longer fixation times, more forward saccades per line of text, and more s accadic regressions. In addition, increased reading difficulty significantl y correlated with a scale of dementia severity in the patients with AD. Con clusions: This pattern of eye movements corresponds to increased text diffi culty and probably represents difficulty with lexical-semantic access in AD . These results suggest that disordered eye movements can signal difficulti es in reading ability in AD even before complaints of reading difficulty or abnormalities on reading tests and may be a means of identifying linguisti c impairment early in this disorder.