Abstract
Purpose: :
Charles Bonnet syndrome (CBS) is a deafferentation syndrome characterised by formed visual hallucinations with retained insight in the context of eye disease. Although a threshold acuity for developing CBS has been previously suggested (Teunisse et al, Br J Psychiatry 1995), no association has been demonstrated between the degree of visual acuity loss and number or type of hallucinatory categories experienced.Glaucoma patients can lose sufficient ganglion cells to develop CBS whilst still maintaining good central acuity (Madill and ffytche, Br J Ophthalmol 2005) unlike AMD patients in who, because axons are lost from the central retina, CBS is invariably associated with a reduction in acuity. We therefore decided to investigate the correlation between acuity and the number of hallucinatory categories experienced in a group of glaucoma patients with CBS.
Methods: :
A cross-sectional study. 10 participants with CBS secondary to glaucoma (mean age 83 years) had their visual hallucinations categorized using the Institute of Psychiatry Visual Hallucinations Interview. Acuities were converted into a bilateral acuity score as a surrogate measure of deafferentation (median acuities OD 0.5, OS 0.6). Correlation between number of hallucinatory categories and acuity score was calculated using SPSS version 18.
Results: :
The number of hallucinatory categories experienced correlated with visual acuity (Pearson coefficient, p=0.037), more categories reported by patients with worse acuity.
Conclusions: :
This is the first study to demonstrate an association between the degree of visual impairment and hallucinatory phenomenology in CBS
Keywords: neuro-ophthalmology: cortical function/rehabilitation