The purpose of the current paper is to consider whether non-pharmacological interventions, specifically promoting physical activity, would benefit people with Charles Bonnet Syndrome (CBS). Although physical activity is known to benefit health generally, its ability to impact on symptoms of specific types of ocular pathologies, such as CBS has not been explored previously.
CBS is a condition in which people with un-correctable vision loss experience hallucinations [1, 2, 3, 4]. Around 1 million people in the UK suffer from CBS [5] as the condition can occur following a number of different ocular pathologies. To receive a diagnosis of CBS, an individual must have a vision impairment that has been officially diagnosed by a professional, and there are specific criteria to be met such as visual hallucinations which occur in the absence of neuropsychiatric disorders such as schizophrenia [6]. While visual loss is a fundamental criterion for a CBS diagnosis, the extent of vision loss required to experience visual hallucinations has not yet been systematically studied [7]. There has been no significant association found with any particular ophthalmic condition, gender, or social circumstances [8]. A large-scale study in the Netherlands found the prevalence of CBS in patients with low vision to be approximately 11%, with hallucinations occurring in patients with a visual acuity in the better eye of 0.3 LogMAR or less. Others have suggested a similar cut off for visual acuity of 20/50 (6/15 or 0.4 LogMAR) or worse being associated with visual hallucinations [9].
Theoretically, in people with CBS, the absence of adequate incoming information, results in the visual parts of the brain compensating for the lack of input by constructing its own images, which are termed hallucinations [3]. The hallucinations experienced in CBS can be very realistic. Emotional reaction, both positive and negative, to the hallucinations may also occur. Hallucinations are characterized by the vivid perception of realistic objects or people that tend to recur in the absence of external stimuli. People with CBS experience two main types of hallucinations. The first type is simple patterns or shapes that are repeated, such as grids, lines, and brickwork patterns, as well as basic imagery like lights and colours. The second type is more complex hallucinations, including objects, buildings, people, landscapes, or specific scenes [10].
There is a considerable lack of awareness surrounding CBS and as a result there is an underlying stigma attached to the experience of hallucinations. Mistakenly, the hallucinations experienced in CBS are often associated with mental health complications. The hallucinations experienced by patients with CBS have no psychiatric or cognitive basis [8, 11]. Furthermore, the visual experiences of those with CBS differ from the kinds of hallucination experienced by patients who suffer from psychosis, in that CBS patients are aware that the visual disturbances are not real. Indeed, the absence of insight towards the visual hallucinations or the presence of a cognitive decline are criteria for a differential diagnosis of conditions such as dementia [12]. Despite awareness that the visions are not real, the hallucinations can evoke unrest as the images themselves can be disturbing. The imagery can also interfere with daily life activities.
Despite the hallucinations of people who suffer CBS being well documented, there is little research regarding the kinds of intervention that may help to reduce the impact of CBS on everyday life. Limited rehabilitation options exist in the UK, with just a small range of visual, pharmacological and social management options that have been subjected to uncontrolled trials [13]. For example, there are a small number of reports that the hallucinations can be reduced using various psychiatric drugs [14, 15, 16]. However, it is important to note that these drugs often have a list of side effects and may not be suitable for the elderly. More commonly in the UK, intervention is based around low vision aids and patient [17].
One common observation made by people with CBS is that hallucinations may be worse when tired or stressed (NHS, 2022). Indeed, a study by Hirji (2020) [18] suggested that more frequent hallucinations are associated with higher levels of psychological stress. Physical activity is known to be important for health and psychological wellbeing [19, 20, 21]. The World Health Organisation (WHO) defines physical activity as ‘any bodily movement produced by skeletal muscles that require energy expenditure.’ [22]. This encompasses all types of movement and can be classified into light, moderate, and vigorous activities. Light activity refers to slow walking, standing, and moving around the home. Moderate activities include cycling, walking, and low-intensity exercises like doubles tennis, hiking, or water aerobics. Vigorous activity comprises high-intensity exercises such as martial arts, singles tennis, running or aerobics, and football [23]. The WHO recommends that adults aged 18–64 engage in150-300 minutes of moderate physical activity or 75–150 minutes of vigorous physical activity per week [22]. Whilst physical activity is known to be of benefit to health and wellbeing, the negative health effects associated with a sedentary lifestyle have also been documented, independent of physical activity levels, and include an increase in cardiometabolic and inflammatory risk biomarkers [24].
People with disabilities often spend lower amounts of time engaging in physical activity and then it is more frequently low-intensity physical activity [25,26]. Access to more structured or intense physical activity is limited and there are often barriers and issues of access to suitable provision [25,26,27,28,29]. More specifically, people with vision impairment are reported to have particular issues with movement and physical activity and these may predispose them to lead a sedentary lifestyle. Studies have found lower levels of activity in school-age individuals with vision impairment, which may be related to the availability of appropriate opportunities. People with vision impairment also take fewer steps and self-report lower levels of physical activity than participants who were normally sighted [25,26, 29]. The correlates of physical activity are complex and vary depending on a number of factors including age, sex, self-efficacy, and motivation [28,30]. Research suggests people would increase their physical activity if they were advised to by an eye-care professional [27]. Nevertheless, environmental factors may be a particular issue for people with visual impairment and there may often be difficulties finding access to suitable facilities [27]. Given that the majority of individuals diagnosed with CBS are elderly they are likely to experience mobility issues.
The perception and experience of stress can be mediated by a number of factors including quality sleep, and exercise [31,32,33,34]. There is a complex relationship between stress and sleep – stress disrupts sleep experience and this effects well-being in a number of ways [35]. The focus of sleep is commonly often the duration and depth of sleep but actually it is the perception of these factors (rather than the reality) that determines how people report their sleep experience [36]. Indeed, Gadie, Shafto, Leng, and Kievit (2017) [35] acknowledge that changes in sleep patterns change over a lifespan and summary measures do not always capture the detail of sleep quality. There are also differences between what has been termed sleep quality and sleep deprivation. Disturbed episodes of sleep are more common than deprivation. The consequence of reduced sleep quality are symptoms such as fatigue, concentration difficulties, reduced physical stamina, memory issues and other symptoms often associated with psychiatric conditions such as distortions of perception and feelings of dissociation. Chronic sleep deprivation can cause people to hallucinate in severe cases [36, 37].
This pilot study considers the role of physical activity and sleep behaviour on the prevalence of hallucinations in people who suffer from CBS. The aim was to determine whether there was any evidence to suggest that the quantity or type of exercise and/or sleep experience could impact on the experience of visual hallucinations in patients who suffer from CBS. A survey of people with CBS was conducted that incorporated measures of the type, frequency and duration of hallucinations together with measures of physical activity and sleep experiences. Given that physical activity is associated with the mediation of perceived stress, and better sleep [37] it was predicted that there would be a negative relationship between levels of physical activity and hallucinatory experiences.