Barbara Boughton

October 30, 2009

October 30, 2009 (San Francisco, California) — Unexplained vision loss — particularly when it arises with symptoms such as difficulty reading and writing — can be a sign of an unusual type of dementia called visual variant of Alzheimer's disease.

Although the condition is uncommon, it is important that ophthalmologists be aware of the disease and its clinical signs so they can make appropriate referrals, according to research presented here at the American Academy of Ophthalmology Joint Annual Meeting With the Pan-American Association of Ophthalmology.

"Many of the patients we studied had already seen 2 or 3 ophthalmologists and still did not have a diagnosis," said Pierre-François Kaeser, MD, an ophthalmologist at the Jules Gonin Eye Hospital in Lausanne, Switzerland.

The disease can be difficult to diagnose because standard eye exams, such as visual acuity, slit lamp, and fundus examination, are often normal, although the visual field can be altered, he explained. Ophthalmologists play an important role in identifying the disease because they're often the first physicians to probe for the reasons behind these patients' visual loss, Dr. Kaeser noted.

Unexplained visual loss should prompt ophthalmologists to administer several easy and quick office tests that can help strengthen the suspicion of visual variant of Alzheimer's disease. If abnormal, patients should be referred to a neurologist or neuro-ophthalmologist.

In their study, Dr. Kaeser and colleagues performed a retrospective chart review that covered cases from 2002 to 2008, and found 10 with unexplained visual loss. They performed complete neuro-ophthalmologic assessments on all 10 patients, including vision tests, neuropsychological testing, and cerebral imaging, such as magnetic resonance imaging (MRI), positron emission tomography (PET), or single photon emission computed tomography (SPECT). They also assessed simultanagnosia and the patients' abilities on simple cognitive tests, including mental calculations, writing, and reading abilities.

Most of the patients sought medical care because they had trouble reading; others also had difficulty writing, and 2 reported a visual blur. Three patients described difficulties with memory. When the researchers used tests such a slit lamp, visual acuity, fundus, and color naming, the results were normal. However, visual field testing showed homonymous visual fields in 8 of 10 patients, and tests involving Ishihara plates were abnormal. Results indicated that most of the patients had dyslexia, dysgraphia, and simultanagnosia, and 6 of 10 exhibited signs of dyscalculia. Seven of 10 patients had altered scores on the Mini-Mental State Examination, and MRIs of all 10 patients indicated parieto-occipital cortical atrophy. On functional imaging, such as SPECT and PET, 7 patients showed hypometabolism or hypoperfusion in the parieto-occipital region.

Dr. Kaeser suggested that ophthalmologists can help identify those with visual variant of Alzheimer's disease by administering several simple office tests along with ophthalmologic exams. These include tests of simple arithmetic, writing, and the ability to read one's own handwriting, and the assessment of the ability to recognize complex images.

Visual variant of Alzheimer's disease tends to have a different course than that seen in typical Alzheimer's disease patients. Patients tend to be younger, usually in late-middle age, have mild or no cognitive dysfunction early in the disease, and have visual symptoms that can't be explained by an ocular abnormality.

The disease was first identified in the late 1980s by D. Frank Benson, MD, in a paper in the Archives of Neurology (1988;45:789-793), which reported 5 cases at a clinic at the University of California-Los Angeles. Although memory and personal insight were retained by most of these patients until late in the course of their disease, visual agnosia, alexia, and acalculia were severe. In 1 patient, difficulties surfaced when he could no longer read what he produced in his job as a bank executive; another patient — a college-educated published author — first noticed that she made errors when she was typing. Her handwriting also deteriorated. The eventual diagnoses were psychologically difficult for these patients, since they retained insight into their visual and cognitive difficulties and the progressive nature of their disease, Drs. Benson and fellow authors wrote.

Neuro-ophthalmologist Benjamin Osborne, MD, assistant professor of neurology and ophthalmology at Georgetown Hospital in Washington, DC, agreed that visual variant of Alzheimer's disease is rare, but noted that he has seen 3 instances in the past 4 years in his practice. "Unfortunately, there are no good treatments for either the Alzheimer's disease or the vision loss," said Dr. Osborne. However, it's important to educate the family and the patient about the disease so they can adapt to visual difficulties, including problems with visual field and driving, Dr. Osborne noted. Occupational therapy and other social services are often vital in helping these patients and their families deal with the vision loss, he said.

Dr. Kaeser and Dr. Osborne have disclosed no relevant financial relationships.

American Academy of Ophthalmology Joint Annual Meeting With the Pan-American Association of Ophthalmology (AAO-PAAO): Abstract PO171. Presented October 25, 2009.

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