Prevalence of Charles Bonnet syndrome in patients with glaucoma: a systematic review with meta-analyses.

Glaucoma is a widespread sight-threatening condition often only recognized when very pronounced. It is initially characterized by peripheral visual field losses, while advanced stages also affect the central vision. Some of these patients may experience visual hallucinations, the Charles Bonnet syndrome (CBS). In this systematic review and meta-analysis, we provide an overview of the literature dealing with the prevalence of CBS in patients with glaucoma. We searched the databases PubMed/MEDLINE, Embase, Web of Science, the Cochrane Central and PsycInfo on 22 March 2020. Eight studies (n = 827 patients) were identified and included for a qualitative and quantitative analysis. No studies included a representative sample of patients with only glaucoma. In patients with glaucoma in different stages and with ocular comorbidities, prevalence of CBS was 2.8% (CI95%: 0.7-6.1%). Among patients with glaucoma where all had bilateral low visual acuity, prevalence of CBS was 13.5% (CI95%: 8.4-19.6%). In patients with glaucoma who visited vision rehabilitation clinics, presumably due to an extensive vision impairment, prevalence of CBS was 20.1% (CI95%: 16.8-23.6%). Risk factors of CBS besides low vision were high age, female gender, reduced contrast sensitivity and not living alone. Taken together, we find that CBS may not be rare in patients with advanced glaucoma with and without ocular comorbidities. However, limitations of the current literature should be highlighted and careful approach towards conclusions is important. More studies are needed to better understand the prevalence and risk factors among different populations of patients with glaucoma.