Charles Bonnet Syndrome in Patients with Open-Angle Glaucoma: Prevalence and Correlation to Visual Field Loss

Abstract

To determine the prevalence and characteristics of Charles Bonnet Syndrome (CBS) and its relation to visual field loss (VFL) in patients with open-angle glaucoma (OAG). Prospective, cross-sectional study. Adult patients (n= 337) with manifest OAG with verified VFL and without significant macular disease or extraocular conditions known to cause visual hallucinations. Patients attending the glaucoma outpatient department of the Skåne University hospital, Malmö, Sweden, between April 1, 2018, and December 31, 2018, were consecutively evaluated for inclusion. Potentially eligible patients admitting to having complex visual hallucinations were interviewed to explore the characteristics of their hallucinatory experiences. Recent automated visual field examinations were available for all participants, and swept-source OCT was performed in participants with CBS to rule out previously undiagnosed macular pathology. The correlation between potential risk factors and CBS was evaluated with logistic regression analysis. Prevalence of CBS in patients with OAG. Charles Bonnet Syndrome was found in 7.1% (95% confidence interval [CI], 4.7-10.6) of patients with OAG. Participants with CBS were more likely to have at least 1 eye with a visual field index (VFI) of ≤30% compared with those without CBS (71% vs. 34.2%; P= 0.001). Although the best-corrected visual acuity (BCVA) in the worse eye was significantly lower in participants with CBS (decimal equivalent of Snellen BCVA: 0.25 vs. 0.6, P= 0.003), 33% of these participants had a BCVA of ≥0.5 in the worse eye. In multivariable analysis, CBS was correlated to the VFI of the better eye (odds ratio, 0.984; 95% CI, 0.969-0.998, P= 0.030) and the BCVA of the worse-seeing eye (odds ratio, 0.210; 95% CI, 0.046-0.952, P= 0.043). Charles Bonnet Syndrome was not a rare condition in patients with glaucoma. Patients with a combination of advanced VFL and low BCVA had the highest risk of CBS; however, 1 of 3 patients with CBS hada BCVA of ≥0.5 in both eyes. These findings emphasize the importance of being attentive to symptoms ofCBS in patients with glaucomatous VFL even when visual acuity is preserved.