Low-vision patients should be warned of Charles Bonnet syndrome

Can J Ophthalmol. 2009;44(1):49-52.

Patients with low visual acuity are more likely to experience visual hallucinations or phantom vision, the hallmark signs of Charles Bonnet syndrome, according to a study.

In 258 subjects with low vision and 251 matched controls with little or no vision loss, Charles Bonnet syndrome was diagnosed in 87 low-vision subjects (34%), but in only four control subjects (1.6%). Charles Bonnet syndrome occurred in patients with various visual acuities, but patients with visual acuity between 20/301 and 20/800 were twice as likely to have the visual disturbances.

Age-related macular degeneration was the most common cause of low vision, but there was not a statistically significant difference in prevalence according to the cause of low vision.

Patients described having episodes between one and 30 times a month, with an average of 10 episodes, but only eight of 87 subjects (9%) reported seeking medical advice. Of those seeking a medical opinion, only half said they were given an explanation for their symptoms. Episodes were reported to occur most frequently between 6 a.m. and noon and between 6 p.m. and midnight.

"The results of the present study show that no treatment is necessary, but it is imperative that ophthalmologists and their staff explain the nature of [Charles Bonnet syndrome] to patients and offer reassurance that this is a common phenomenon," the study authors said.