Visual hallucinations are well recognized in individuals with low vision and intact cognition (Charles Bonnet syndrome) (Teunisse et al., Reference Teunisse, Cruysberg, Hoefnagels, Verbeek and Zitman1996). Visual hallucinations also occur in those with early manifestations of dementia with Lewy bodies (McKeith et al., Reference McKeith2005) and Parkinson's disease dementia (Williams and Lees, Reference Williams and Lees2005). Typically, visual hallucinations in these conditions are complex recurrent hallucinations of people and animals and frequently reported as being unpleasant (Mosimann et al., Reference Mosimann2006). Individuals with visual hallucinations are often reluctant to disclose details of their symptoms (Menon, Reference Menon2005), but may instead report non-specific visual difficulties to their family physician or optometrist, resulting in referral to an eye clinic. Failure to elicit the presence of visual hallucinations may lead to inappropriate treatment of age-related ocular comorbidity, such as early cataract.
In order to the evaluate the use of a single question to elicit symptoms of visual hallucinations, we asked 50 consecutive patients, aged over 70 years, who had been referred to the general ophthalmology clinic for consideration for cataract surgery, the following standardized question, which attempts to normalize the experience of hallucinations:
“It is common for the eyes of patients with visual difficulties to play tricks on them so that they see things that are not really there. Does this ever happen to you?”
We recorded their answer to this question and if they answered “yes” then details of their visual experiences were explored. No one refused to answer the question or expressed offence at being asked about visual hallucinations in this way.
We found that 13 of the 50 patients answered “yes” to the above question. Three had complex visual hallucinations of animals or insects; the remaining 10 experienced presence or passage hallucinations. Those with presence hallucinations (n = 8) described the vivid sensation of the presence of a person or object in the room; those with passage hallucinations (n = 3) described brief visions of an animal or object passing sideways (Fenelon et al., Reference Fenelon, Mahieux, Huon and Ziegler2000). No referral letters mentioned visual hallucinations and in no cases were the symptoms volunteered without direct questioning. For all those patients who were experiencing complex visual hallucinations, referral to a psychiatrist was made.
We conclude that undisclosed visual hallucinations are common among older people presenting to general eye clinics, with over a quarter of patients admitting to visual hallucinations in this sample. Visual hallucinations are rarely brought to light by the referral letter or indirect questioning. However, we found that a single, simple question which attempts to normalize the experience of visual hallucinations was acceptable to our patient sample, and successful in eliciting these symptoms in a significant number of people referred for cataract surgery. A limitation of our study in asking patients about “seeing things that are not really there” is that it may fail to elicit visual hallucinations in those patients who are experiencing visual hallucinations but who are convinced that the images are real. The sensitivity of the question could be improved by asking it in the presence of a family member, friend or spouse who knows the patient well.
For some, visual hallucinations may be the undisclosed reason for seeking an ophthalmic consultation. Failure to elicit this agenda may lead to inappropriate investigation or treatment of age-related comorbidity. In most of our cases, visual acuity was only moderately reduced. In the absence of formal cognitive assessment, it is not possible to exclude a neurodegenerative cause for the hallucinations experienced by our patients. Clinicians should be aware of this phenomenon when assessing older people with visual symptoms and encourage patients to disclose hallucinations. If present, patients may need further investigation for any potential underlying neurodegenerative cause.
Conflict of interest
This work was supported by the UK NIHR Biomedical Research Centre for Ageing and Age-related Disease award to the Newcastle upon Tyne Foundation Hospitals NHS Trust.