Vision Problems and Variant AD

Contributed by: Michael Rafii, M.D., Ph.D - Director of the Memory Disorders Clinic at the University of California, San Diego. ______________________________________

In a minority of Alzheimer's patients the disease shows up first as problems with vision rather than memory or other cognitive functions. But diagnosis can be difficult because standard eye exams are often inconclusive for these patients.

Neuro-ophthalmologists Pierre-Francois Kaeser, MD, and Francois-Xavier Borruat, MD, Jules Gonin Eye Hospital, Switzerland, examined and followed 10 patients with unexplained vision loss who were ultimately diagnosed with the visual variant of Alzheimer's disease (VVAD). Their study -- presented at the 2009 Joint Meeting of the American Academy of Ophthalmology and the Pan-American Association of Ophthalmology (PAAO) -- describes clinical clues that may improve ophthalmologists' ability to detect VVAD and refer patients for further tests. When patients receive neurological assessment, treatment and family counseling early in the disease, outcomes may be better for all concerned.

VVAD patients differ from typical Alzheimer's patients in a number of ways. At the time they report visual problems, many are younger than those for whom memory loss is the tell-tale sign. In Dr. Kaeser's study the median patient age was 65, and only 3 of 10 reported memory loss. In comprehensive neuro-ophthalmic exams even though most patients' visual acuity was adequate, all but one had difficulty with reading, 8 of 10 with writing, and 6 of 10 with basic calculations. The visual field was altered in 8 of 10 patients.

All had trouble identifying colored numbers despite being able to name colors correctly, and, importantly, 8 of 10 patients had difficulty recognizing and interpreting components of a complex image (simultagnosia). This is an early indicator of the brain damage that prevents later-stage Alzheimer's patients from recognizing people they know and navigating familiar surroundings. MRI and PET scans revealed neurological changes consistent with VVAD in all study patients. Though VVAD patients' first symptoms are visual, Alzheimer's memory and personality impairments eventually occur in most.

Interestingly, in the neurology field VVAD is referred to as Posterior Cortical Atrophy (PCA), because the posterior, or back of the brain, shrinks. When pathologists examine the brain tissue from these patients, they see amyloid plaques in the occipital lobe, which is in the posterior part of the brain, and resposible for vision.