Charles Bonnet Syndrome in patients with open-angle glaucoma - prevalence and correlation to visual field loss.

Abstract Purpose 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). Design Prospective, cross-sectional study. Participants Adult patients (n=337) with manifest OAG with verified VFL and without significant macular disease or extraocular conditions known to cause visual hallucinations. Methods Patients attending the glaucoma outpatient department of the Skane University hospital, Malmo, Sweden, between April 1st 2018 and December 31st 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 optical coherence tomography 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. Main outcome measure Prevalence of CBS in patients with OAG. Results CBS was found in 7.1% (95% CI: 4.7% - 10.6%) of patients with OAG. Participants with CBS were more likely to have at least one eye with a visual field index (VFI) of ≤ 30% compared to 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). Conclusions CBS 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, one out of three patients with CBS had a BCVA of ≥ 0.5 in both eyes. These findings emphasize the importance of being attentive to symptoms of CBS in patients with glaucomatous VFL even when visual acuity is preserved.