Patients with VVAD experience visual comprehension problems, which can’t be fixed with glasses or surgery.
Where are those darn car keys? Why can’t I remember her name? Fears of Alzheimer’s disease have us all second-guessing even the most routine of memory lapses. Indeed, impaired memory is one of the classic early signs of Alzheimer’s disease.
But in a few people, memory problems aren’t the first sign of trouble. Instead, the first sign of Alzheimer’s disease is a problem with vision, or more accurately, a problem with visual comprehension. A person in the early stages of Alzheimer's disease may end up in an ophthalmologist’s office complaining, "I can’t see,” or even, "I can see, but I can’t read or write.” Depth perception may be off, leading to falls and other accidents.
People with these symptoms may have what’s known as the visual variant of Alzheimer's disease, or VVAD. While VVAD is relatively uncommon today, it is expected to become more prevalent as the U.S. population ages and more people develop Alzheimer’s disease. Because the visual comprehension problems come first in VVAD, ahead of those related to memory, people who are affected may consult an ophthalmologist first, thinking that they just need new glasses or even cataract surgery.
Whenever a person claims that he or she "can’t see,” an ophthalmologist begins by assessing the person’s visual acuity and visual fields. While some people with VVAD do show some degree of visual field loss, others have normal eye exams. In a study of eight patients with VVAD, for instance, only half had any visual field loss. Moreover, the person’s visual acuity may be as good as 20/20. In other words, the problem is not that people with VVAD can’t see what’s in front of them, it’s that their brains aren’t accurately processing the information.
Once an ophthalmologist suspects VVAD, the individual will be referred to a neurologist for further evaluation and treatment. While the visual symptoms may be the initial -- or in rare cases, the only -- sign of Alzheimer’s disease, it does appear that most people with VVAD go on to develop the classic symptoms of Alzheimer’s disease, including impaired memory and personality changes.
It’s also important to note that many people with Alzheimer’s disease who first experience memory problems typically develop visual problems later on. For instance, these Alzheimer’s disease patients often develop problems with contrast sensitivity or visual attention. Contrast sensitivity involves the ability to detect different shades of gray. It’s an important consideration with nighttime driving, for instance, but it also helps us "read” complex surfaces.
Visual attention has several components: It refers to our ability to detect and identify objects in space, to pay attention to two things at once, and to tune into one type of information while ignoring other less important types of information. Problems with contrast sensitivity and visual attention play a role in the early stages of Alzheimer’s disease, such as problems with driving a car. Later on, they contribute to such well-known problems as being unable to recognize faces or navigate familiar places. As with VVAD, it’s important for family members to understand that the person’s visual problems are part of the Alzheimer’s disease and can’t be fixed with glasses or surgery.
