LETTER TO THE EDITOR
Year : 2013 | Volume
: 17 | Issue : 3 | Page : 534-
The diagnosis of Charles Bonnet syndrome in visual field defects
Louis W Lim1, Kelvin Z Li1, Colin S Tan2,
1 National Healthcare Group Eye Institute, Tan Tock Seng, Singapore
2 National Healthcare Group Eye Institute; Department of Ophthalmology, Tan Tock Seng Hospital, Tan Tock Seng, Singapore
Colin S Tan
National Healthcare Group Eye Institute, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, 308433
|How to cite this article:|
Lim LW, Li KZ, Tan CS. The diagnosis of Charles Bonnet syndrome in visual field defects.Indian J Endocr Metab 2013;17:534-534
|How to cite this URL:|
Lim LW, Li KZ, Tan CS. The diagnosis of Charles Bonnet syndrome in visual field defects. Indian J Endocr Metab [serial online] 2013 [cited 2020 Sep 30 ];17:534-534
Available from: http://www.ijem.in/text.asp?2013/17/3/534/111686
We read with interest the article by Farida et al.  describing Charles Bonnet syndrome (CBS) in a patient with pituitary tumor and agree that physicians should ask about the occurrence of these hallucinations in patients with visual loss or visual field defects. The prevalence of CBS is highly variable in the literature, and depends on the population and type of patients seen. It has been reported to be as low as 0.4% in a general ophthalmology clinic. 
Some authors have suggested that the dynamic change in visual acuity rather than the absolute level of visual acuity may be associated with the occurrence of visual hallucinations. , It is not clear when the hallucinations began in this patient, but it is interesting that these hallucinations persisted for at least a period after tumor shrinkage. It is possible that the increased sensitivity of surviving neurons may have resulted in the any visual stimuli being perceived as hallucinations, and the hallucinations may discontinue once visual recovery ceases. ,
In some patients with visual field defects, the visual hallucinations have been localized to the area of visual field defect.  It would be interesting to know whether the hallucinations in this patient occurred in any particular area of his visual field or if they were more generalized.
It is important to point out that although CBS typically occurs more commonly in older people, it has been described in younger patients  even those in the pediatric age group.  Hence it is important to consider this diagnosis when patients with reduced visual acuity or visual field defects report visual hallucinations.
We agree with the authors that it is important to reassure patients that these hallucinations are known to occur and are not a sign of psychiatric disease. Very often, reassurance is a very important component of the management of CBS and drugs may not be required.  If they are not asked, patients are often reluctant to discuss their symptoms, as they are afraid of being labeled "mad" or have the stigma of a psychiatric disease.  In conclusion, it is very important for physicians to be aware of CBS and gentle reassurance is an important component of its management.
|1||Farida C, Faiza B, Ilyes B, Said A. Charles Bonnet syndrome: An under reported entity in endocrinology. Indian J Endocrinol Metab 2012;16:867-8.|
|2||Tan CS, Lim VS, Ho DY, Yeo E, Ng BY, Au Eong KG. Charles Bonnet syndrome in Asian patients in a tertiary ophthalmic centre. Br J Ophthalmol 2004;88:1325-9.|
|3||Tan CS, Sabel BA, Goh KY. Visual hallucinations during visual recovery after central retinal artery occlusion. Arch Neurol 2006;63:598-600.|
|4||Tan CS, Sabel BA. Dynamic changes in visual acuity as the pathophysiologic mechanism in Charles Bonnet syndrome (visual hallucinations). Eur Arch Psychiatry Clin Neurosci 2006;256:62-3.|
|5||Schultz G, Melzack R. The Charles Bonnet syndrome: 'Phantom visual images'. Perception 1991;20:809-25.|