Visual impairment in Alzheimer's disease: a critical review.

Visual impairment is a common symptom of Alzheimer's disease (AD). Recent studies have demonstrated the potential of visual interventions to improve the functioning of AD patients. Therefore, clarification of the profile of visual deficits in AD and possible mechanisms underlying these deficits are needed. This review focuses on three areas as mechanisms for the visual impairment in AD: 1) the broad-band pathway deficit; 2) glaucoma; and 3) the relative dysfunction of the ventral and dorsal streams of vision. While much research has been produced with regard to these areas, methodological flaws and lack of continuity between studies has led to conflicting findings. Nevertheless, recent imaging research suggests that the loss of retinal ganglion cells in AD may play an important role in the visual deficit in AD. This review looks to critically evaluate current research and highlight the need to investigate recent significant findings in primary vision research in understanding the impairment of vision in AD.