Visual hallucinations in neurological and ophthalmological disease: pathophysiology and management

Abstract

Visual hallucinations are common in older people and are especially associated with ophthalmological and neurological disorders, including dementia and Parkinson’s disease. Uncertainties remain whether there is a single underlying mechanism for visual hallucinations or they have different disease-dependent causes. However, irrespective of mechanism, visual hallucinations are difficult to treat. The National Institute for Health Research (NIHR) funded a research programme to investigate visual hallucinations in the key and high burden areas of eye disease, dementia and Parkinson’s disease, culminating in a workshop to develop a unified framework for their clinical management. Here we summarise the evidence base, current practice and consensus guidelines that emerged from the workshop.Irrespective of clinical condition, case ascertainment strategies are required to overcome reporting stigma. Once hallucinations are identified, physical, cognitive and ophthalmological health should be reviewed, with education and self-help techniques provided. Not all hallucinations require intervention but for those that are clinically significant, current evidence supports pharmacological modification of cholinergic, GABAergic, serotonergic or dopaminergic systems, or reduction of cortical excitability. A broad treatment perspective is needed, including carer support. Despite their frequency and clinical significance, there is a paucity of randomised, placebo-controlled clinical trial evidence where the primary outcome is an improvement in visual hallucinations. Key areas for future research include the development of valid and reliable assessment tools for use in mechanistic studies and clinical trials, transdiagnostic studies of shared and distinct mechanisms and when and how to treat visual hallucinations.

Exacerbation of visual hallucinations in Charles Bonnet syndrome due to the social implications of COVID-19

“…In addition, those reporting a change in their emotional reaction to hallucinations through the pandemic were, 20 Treatment pathways in persistent cases include patient counselling and cognitive-behavioural therapy, with a theoretical basis for pharmacological modification of cholinergic, GABAergic, serotonergic or dopaminergic systems, or reduction of cortical excitability. 21 An important health priority for people with CBS will be to mitigate the impact of the lockdown and subsequent isolation, ensuring they remain socially connected. The challenge will be to ensure all those struggling with visual 'The intensity of the colours and bright lights happens more often, and I see more frightening zombie like faces with blood dripping from the eyes, although all caricature.'…”

Hallucinations in Parkinson’s disease: new insights into mechanisms and treatments

“…The next step is to reduce or stop medications that could be worsening hallucinations and only then to consider specific treatments. 18 Importantly, specific interventions for visual hallucinations should only be initiated if patients are bothered by the experiences, as in most cases, side effects can outweigh benefits of treatment.…”

Hallucinations as intensified forms of mind-wandering

“…Hallucinations are sensory experiences that occur involuntarily in the absence of a matching external stimulation of the relevant sensory receptors, yet are perceived as if they were experiences of external objects or events [25][26][27]. In contemporary literature, there is an abundance of mechanistic models trying to account for this phenomenon, many of which focus on spontaneous sensory hyperactivity and impaired reality monitoring as the major source of hallucinations [28].…”