Visual illusions can be an early symptom of dementia, but in some cases they may be a sign of a purely ophthalmic condition, Charles Bonnet syndrome (CBS). This rare disease describes visual hallucinations that occur as a result of structural damage to the visual pathway in patients without a neuropsychiatric disorder. One of the largest analyses to date on CBS, published in Ophthalmology, shows potential associations with age-related macular degeneration (AMD), glaucoma, and cataract surgery.
Investigators examined 10-year data based on 4203 participants in the Age-Related Eye Disease Study 2 (AREDS 2). They found 12.22% (446) of 3651 individuals who answered questions about CBS symptoms during the study period reported visual hallucinations.
“Taken together, these observations and ours support a call to raise awareness of detection and management of CBS in the ophthalmology community,” according to the analysis. These phantom lines and forms do not typically interfere with visual function, but can affect visual quality of life. The research added that results are most likely an underestimate of actual numbers for those with CBS, due to patients not remembering or reporting the symptoms.
In CBS, the illusions can occur from damage in the visual pathway. “Disruption to visual input may result in an overcompensated response in the visual cortex,” according to the report. An individual’s cognition and neuropsychiatric status are typically normal, and patients are usually aware that extraneous lines, geometric shapes, patterns, or facial images seen are hallucinations. At 10 years, 86% of those with symptoms had been diagnosed with late AMD and 64% had undergone cataract surgery, in either 1 or both eyes.
For affected individuals, 238 participants offered descriptions or drawings of the shapes, with mean time for the imagery lasting 3 years. Nearly 50% of these individuals saw more than 1 type of form, with faces or people most frequently visualized. Participants with symptoms of CBS had an approximately 51% greater likelihood — 14% to 2 times greater likelihood — of experiencing depressive symptoms compared with individuals without CBS symptoms (P =.004). Patients with CBS were not likely to have cognitive impairment (P =.772).
AREDS 2 participants attended annual comprehensive eye examinations for 5 years, and responded to questions in phone interviews between the visits. A 5-year follow-on study included phone meetings twice a year and a 10-year in-person visit.
The research comprised a nondiverse White, well-educated sample. Regarding study limitations, associations involving progressive disorders may change or evolve. Also, some hallucinations could have been due to early Parkinson disease or use of medications such as proton-pump inhibitors. Strengths of this investigation included certified interviewers, centralized grading, and use of validated non-vision-dependent assessments.
“When CBS is suspected, it is important to educate, provide reassurance that hallucinations alone do not indicate underlying neuropsychiatric disorders, and offer simple steps to attempt to decrease hallucination,” according to the analysis.
Le JT, Peprah D, Agrón E, Keenan TDL, Clemons TE, Chew EY, for the AREDS 2 Research Group. Associations between age-related eye diseases and Charles Bonnet syndrome in participants of the Age-Related Eye Disease Study 2: AREDS2 Report Number 26. Ophthalmology. Published online August 19, 2021. doi:10.1016/j.ophtha.2021.08.012