Abstract
Purpose: :
To present a new pathological mechanism to explain symptoms in unilateral Charles-Bonnet Syndrome (CBS).
Methods: :
Case report and discussion and review of the literature.
Results: :
A 64 year old man who suffered from unilateral blindness due to rubeotic glaucoma presented with visual hallucinations in the temporal visual field of the blind eye. These hallucinations always started in and were mostly confined to the far temporal field but sometimes crossed the midline. They were both formed and unformed.They were present with both eyes open and very distressing for the patient. Investigations including MRI of the head were normal. Review of the literature showed very few cases of CBS in unilateral blindness and in only one case was it stated which area of the visual field was affected. In this case symptoms were predominantly in the far temporal field of the blind eye.
Conclusions: :
We suggest that the location of visual hallucinations in the far temporal visual field, the monocular crescent, in unilateral blindness is because the corresponding area of visual cortex has only a monocular input and so has no input at all when the affected eye is blind. We propose that enquiry is made into the location of the visual hallucinations in unilateral Charles Bonnet Syndrome. This condition is often diagnosed late and better characterisation and understanding of the condition would aid diagnosis and avoid unnecessary investigations.
Keywords: neuro-ophthalmology: cortical function/rehabilitation • visual impairment: neuro-ophthalmological disease