INTRODUCTION
Charles Bonnet Syndrome(CBS) was first described in 1760 by Naturalist
and philosopher Charles Bonnet, who first observed lifelike complex
visual hallucinations in his grandfather Charles Lullis after bilateral
cataract surgery(1); it was a neurologist George de Morsier who coined
the term in 1938 after Charles Bonnet himself developed the
condition(2). CBS, also known as ”phantom image”, is characterized by
recurrent or persistent complex visual hallucinations in people with a
disease of the visual system with intact insight, intellectual function
and normal cognitive functioning without primary psychiatric
disorders(3,4). With limited knowledge of CBS among physicians, the
prevalence of CBS is underreported(4) even though 41-59% of the
visually impaired experience elementary visual phenomena, and 11-15%
exhibit complex hallucinations, due to a medical condition or
artificially produced, such as in preparation for cataract surgery(5,6).
The presence of varying inclusion criteria, inconsistent depth of
questioning and limited patient disclosure for fear of being ridiculed
may all contribute to underreporting(3,5). Visual hallucinations could
be a sign of psychiatric disorders, neurological diseases, metabolic
abnormalities, and the use or abuse of specific drugs(7). Both
elementary forms(3) and complex visual hallucinations are reported in
CBS(8); while glaucoma,
cataract and age-related macular degeneration are the most common
associated disorders, any ophthalmological conditions can lead to
CBS(7), especially in significant visual impairment(9). A pituitary
adenoma is rarely associated with CBS (10); however, reduced visual
acuity or a visual field deficit can occur from the benign tumour’s
compressing optic chiasm affecting one or both eyes(11).
There are three main theories associated with the pathogenesis of CBS,
and these are; the sensory deprivation or deafferentiation theory
related to spontaneous excitation due to a loss of visual input to the
brain(12), the release theory associated with excessive excitation and
the consequent release of visual hallucinations(13,14), and the
”irritative theory” due to distal provocative injuries transmit
abnormal input to the visual cortex leading to abnormal excitatory
activity to the temporal and occipital lobes(15,16).
Charles Bonnet syndrome is treated multifacetedly with pharmacotherapy,
psychosocial therapy, maintaining appropriate eye care, and sensory
stimulation. Generally, CBS is treated with antipsychotics and
antidepressants(5), and in some cases, antiepileptic medications have
also been used with variable benefits (17).
An 81-year-old blind male presented with a three-year history of visual
hallucinations after a recurrence of pituitary macroadenoma. His past
psychiatric history is uneventful, and he has intact insight with no
cognitive impairment. He improved on a low haloperidol dosage, with a
few relapses, when he stops the medications.