I read with interest the article on Charles Bonnet Syndrome (CBS) by Cinar et al. However, I wish to make the following observations:
In the article, visual deterioration has been mentioned as one of the components of the triad to define CBS. The authors have rightly taken pains to confirm the other components of the triad, such as the normalcy of cognition by conducting neurological examination, electroencephalography, magnetic resonance imaging and mini-mental state examination, but, surprisingly, there is no mention of the best corrected visual acuity or a proper ophthalmological examination. As the patient was an 80-year-old and the medical history was significant for diabetes and hypertension, there could have been other associated ocular conditions such as age-related macular degeneration or diabetic retinopathy. Although glaucomatous vision loss can cause CBS, macular degeneration is supposed to be the most common condition associated with this syndrome, and could have been the primary cause, along with glaucoma as the secondary cause. Improvement in blood sugar can also lead to a decrease in visual hallucinations in CBS but, in this study, the glycemic status of the patient or the details of the medication history have not been given.
The authors have written that their patient was started on a daily dose of 75 mg of pregabalin for diabetic neuropathy. It is unclear from the sentence whether the patient was primarily treated for diabetic neuropathy or CBS. If CBS was managed in the process of treating the diabetic neuropathy, then the 75 mg dose seems less than the dose usually recommended for neuropathy, to begin with. Otherwise, the reasons for choosing pregabalin for treating CBS, such as the previous success of gabapentin in CBS and it being a safer congener with established efficacy in neuropathy also, should have been elaborated a little more.
1. Cinar N, Sahin S, Karsidag S, Cinar N, Sahin S, Karsidag S. Eye-related visual hallucinations: Consider ‘Charles Bonnet syndrome’ Indian J Ophthalmol. 2011;59:229–301
2. Jacob A, Prasad S, Boggild M, Chandratre S. Charles Bonnet syndrome-elderly people and visual hallucinations BMJ. 2004;328:1552–4
3. Gray M, Jones IR. Type II diabetes mellitus presenting as the Charles Bonnet syndrome J R Soc Med. 1997;90:503
4. Freeman R, Durso-Decruz E, Emir B. Efficacy, safety, and tolerability of pregabalin treatment for painful diabetic peripheral neuropathy: Findings from seven randomized, controlled trials across a range of doses Diabetes Care. 2008;31:1448–54