Prevalence of visual hallucinations in a national low vision client population

Purpose: To evaluate the prevalence of visual hallucinations (Charles Bonnet syndrome) in a national population undergoing vision rehabilitation.

Study design: Cross-sectional survey.

Participants: Participants were 2565 new clients older than 40 years attending a Canadian National Institute for the Blind (CNIB) vision rehabilitation clinic.

Methods: Participants were asked the following question: "Many people who come to CNIB tell us that they see things they know are not there. Some see patterns or shapes. Others see images of people or animals. Have you ever experienced this?" Responses were cross-tabulated on the basis of age, sex, eye disease, visual acuity, and whether the clients lived alone. Multivariable logistic regression was used to analyze the responses.

Results: Overall, 18.8% of people surveyed indicated that they had experienced hallucinations. In the multivariable model, females showed higher odds of hallucinations than males did (odds ratio [OR] 1.32, 95% CI 1.06-1.64, p = 0.02). Clients with greater vision loss had higher chances of experiencing hallucinations than those with the lowest level of vision loss (OR 1.49, 95% CI 1.19-1.88, p = 0.0005). There was no significant difference in the chances of experiencing hallucinations between people with age-related macular degeneration, diabetic retinopathy, and glaucoma, or in older versus younger respondents. People who did not live alone had higher chances of experiencing hallucinations than those who lived alone (OR 1.54, 95% CI 1.19-1.98, p = 0.0009).

Conclusions: Visual hallucinations are experienced by approximately 1 in 5 patients with vision loss caused by any eye disease, warranting greater awareness of the phenomenon among all vision health professionals and their patients.