COMPLEX VISUAL HALLUCINATIONS IN PATIENTS REFERRED FOR CATARACT SURGERY.

To investigate the prevalence and clinical characteristics of complex visual hallucinations in patients referred for bilateral cataract surgery.

A single-center tertiary cataract clinic at the department of Ophthalmology, Copenhagen University Hospital Rigshospitalet, Glostrup, Denmark.

Three hundred patients were included in this prospective, cross-sectional study. Following a thorough clinical assessment, all participants were screened for visual hallucinations using the same question. Participants responding positively were further questioned about the characteristics of their hallucinatory experiences. Previous medical history was available through digital patient records. Patients with known or suspected cognitive disability or neuropsychiatric disease were excluded, as were patients unable to speak and comprehend the Danish language. 

Fourteen (4.7 %) participants reported experiencing complex visual hallucinations (VH). Of these, 8 (2.7 %) saw hallucinations attributable to Charles Bonnet syndrome (CBS), while the remaining 6 (2.0 %) had hypnogogic or hypnopompic hallucinations. Participants who experienced complex visual hallucinations had statistically lower best corrected visual acuity in their best seeing eye compared to participants without hallucinations (mean visual acuity 0.47 (SD 0.20) vs. 0.58 (SD 0.17), p=0.018). No differences were observed in best corrected visual acuity in the worst seeing eye. No significant differences in age, gender or BCVA was observed between participants who experienced CBS and hypnogogic or hypnopompic VH. When participants with a BCVA > 0,3 were excluded, the prevalence of complex VH rose to 10.3 %. One participant with CBS suffered slight distress. Three patients with complex VH had coexisting ocular morbidity: one had glaucoma, two had AMD. Only 15 (5.0 %) patients were familiar with the co-occurrence of complex visual hallucinations due to eye disease, i.e. CBS. 

Complex visual hallucinations are frequently observed in patients attending a cataract clinic, even after excluding extraocular conditions known to cause visual hallucinations, e.g. dementia. The prevalence is even higher in patients with poor visual acuity. Considering the ubiquity of cataract in elders, and the possibility of hallucinatory distress and misdiagnosis of VH, it is important to be familiar with visual hallucinations and their potential consequences in patients with cataract.