Not Crazy Just Seeing Things
WILLIAM TOWNSEND, OD
Mrs. G presented
to our office with a history of severe geographic macular degeneration. This 83-year-old
established patient was otherwise alert, well-oriented and in remarkably good health.
I began to question her about the primary reason for her visit, she calmly
said, "My kids think I'm crazy, and they want to have me committed." She went on
to describe seeing "people who aren't there, trees and branches that don't exist
and patterns on the walls." Visual acuities were 10/300 OU and confrontation fields
were full, but FDT showed a central scotoma. All other neurological tests were normal.
Dilated fundus examination showed 2.5 disc diameter areas of RPE dropout consistent
with geographic AMD. The optic nerves and other fundus features were unremarkable.
We diagnosed Mrs. G with Charles Bonnet Syndrome (CBS), first
described in 1760 by Swiss philosopher Charles Bonnet, whose visually impaired grandfather
described seeing animals and buildings that Bonnet couldn't see. An estimated 13
percent of patients who have AMD experience some degree of CBS. Sensory deprivation
(living alone), diminished cognitive abilities, stroke, aging and depression can
exacerbate the disease. CBS occurs when people who have vision loss see objects
that they intellectually know aren't real. The onset usually occurs soon after an
episode of vision loss or worsening of existing visual impairment.
Two primary patterns of visual hallucination may affect individuals
who have CBS. First is the occurrence of repetitive patterns such as mosaics or
tree branches. Second is the appearance of people or faces, either normal in size
or reduced. Our patients have reported seeing animals or even dragons as part of
The precise etiology of CBS is unknown, but clinicians theorize
that it occurs in response to sensory stimulation. A similar situation exists in
individuals who have lost limbs. They complain of pain, cold or tingling in limbs
that have been amputated.
It's important to differentiate between CBS and other conditions
that present with visual hallucinations. Between eight percent and 40 percent of
patients undergoing long-term treatment for Parkinson's disease will have visual
hallucinations. They're also the most common type of hallucination in dementia,
a syndrome characterized by multiple cognitive deficits and severe memory loss.
Alpha-adrenergic anti-hypertensives such as clonidine, the anti-convulsant
carbamazepine, analgesics such as pentazocine and fentanyl, and anti-vertigo drugs
such as diphenidol may cause hallucinations. Selective serotonin re-uptake blocker
antidepressants (SSRI) and some histamine-2 blockers used to treat gastric disease
may also generate hallucinations.
Space-occupying lesions in the brain, particularly occipital lobe
tumors, may cause hallucinations. When patients present with visual hallucinations
not associated with seizures, make every effort to rule out an occipital lobe lesion.
Making the Diagnosis
When patients present with complaints of visual hallucinations,
it's vital to establish whether the cause is organic or benign. If patients recognize
that their experience isn't real, but rather imagined, this suggests CBS. Careful
evaluation of the individual's mental status, ability to verbalize, comprehend and
think rationally can help you determine if the likely cause of visual hallucinations
is CBS or another, more threatening condition.
Dr. Townsend is in private
practice in Canyon, Texas, and is a consultant at the Amarillo VA Medical Center.
E-mail him at email@example.com.
Contact Lens Spectrum, Issue: September 2005