Alzheimer's and Vision Problems, The Alzheimer's Library
"More than 60 percent of the people with Alzheimer's have a decline in one or more visual capacities. Problems most commonly occur in four areas: motion, depth, color and contrast. And like other Alzheimer's symptoms, not everyone with the disease will experience visual and perceptual problems to the same degree."
"It's important for caregivers to understand what people with Alzheimer's may be "seeing" when they look at an object and how that differs from what the caregivers see when they look at the same object. Once that knowledge is gained, steps can be taken to increase safety and lessen confusion."