Characteristics of exploratory eye movements in elderly people: possibility of early diagnosis of dementia

Background: Visual cognitive dysfunction is one of the most important signs indicating the early stage of dementia. Thus, visual testing could be used as an aid to the clinical diagnosis of dementia. In the present study, exploratory eye movement was measured to evaluate visual cognitive function in elderly subjects, including those with dementia. Methods: We analyzed responsive search scores (RSS) from exploratory eye movements of 300 subjects who were examined with an eye mark recorder while viewing S shaped figures. Subjects were divided into three groups (dementia, intermediate, healthy) from the values of the Revised Hasegawa Dementia Scale (HDS-R), the Mini-Mental State Examination (MMSE) and the Clinical Dementia Rating. We further divided the intermediate groups into two subgroups, the high score and low score groups, based on RSS. In 202 subjects, Z-scores of voxel-based specific regional analysis system for Alzheimer's disease (VSRAD) were obtained from magnetic resonance imaging (MRI). Results: RSS of the dementia group were significantly lower than those in the intermediate and healthy groups, in order: dementia < intermediate < healthy groups. RSS of the low score intermediate group was significantly lower than that of the high score intermediate group. There was no significant difference between the low score intermediate and dementia groups, or between the high score intermediate and healthy groups. No significant differences of either HSD-R or MMSE were observed between the low score and the high score intermediate groups. The Z-score of VSRAD using MRI in the low score intermediate group was significantly higher than that in the high score intermediate group. Conclusions: These findings suggest that RSS using an eye mark recorder is a useful psychophysiological marker to evaluate the early stage of dementia as well as at-risk elderly people.