Hutchinson CV, Badham SP
College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, UK
To experimentally assess visual attention difficulties commonly reported by those with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
Twenty-nine ME/CFS patients and 29 controls took part in the study. Performance was assessed using the Useful Field of View (UFOV), a spatial cueing task and visual search.
Patients and controls performed similarly on the processing speed subtest of the UFOV. However, patients exhibited marginally worse performance compared with controls on the divided attention subtest and significantly worse performance on the selective attention subtest. In the spatial cueing task, they were slower than controls to respond to the presence of the target, particularly when cues were invalid. They were also impaired, relative to controls, on visual search tasks.
We have provided experimental evidence for ME/CFS-related difficulties in directing visual attention. These findings support the subjective reports of those with ME/CFS and could represent a potential means to improve diagnosis.
This research was funded by ME Research UK and the Irish ME Trust.
Comment by ME Research UK
Around three-quarters of people with ME/CFS report problems with their eyes and vision – but you wouldn’t know it from the mainstream scientific literature, which rarely mentions these important symptoms (see the overview below). In order to redress the balance, the Vision and Language Research Group, University of Leicester – with funding from ME Research UK and the Irish ME Trust – has been busy trying to identify and quantify vision-related problems in the disease. This scientific paper presents the first of their findings – and it makes fascinating reading.
In this publication, researchers Dr Claire Hutchinson and Dr Steve Badham describe the specialised and quite intricate measurements undertaken on 29 ME/CFS patients and 29 matched healthy controls across 3 specific aspects of vision: a) visual processing speed, divided attention, and selective attention; b) spatial cueing (the ability to shift attention); and c) visual search (the ability to locate a target in a field of ‘distractors’).
Overall, patients performed worse than healthy people in each of these specific areas – they were less able to selectively attend to a specific target while ignoring other irrelevant information; they were slower when it came to moving their attention to a target (particularly a target appearing at an unexpected location); and they were slower at scanning visual stimuli and more easily affected by ‘distractors’ during a visual search.
While these findings provide much-needed experimental evidence of visual impairments in ME/CFS and support patients’ own reports, the causes of these anomalies remain unknown. It may be that processing speed is impaired, given that reaction times are known to be affected in the illness (see Cognitive functioning; a meta-analysis). However, the researchers suggest that problems with eye movement itself might underlie some of these observations, and their next publication is likely to be on this particular aspect.
Overview: signs and symptoms in the eyes
In the early 1990s, two reports appeared in the scientific literature reporting ocular (eye) symptoms in ME/CFS. In the first (published in Optometry and Vision Science, 1992), a research group in Boston, Massachusetts surveyed 190 patients and 198 healthy controls by written questionnaire, and found a range of eye-related symptoms which they grouped into four categories: functional (related to accommodation and convergence); neurosensory (such as headaches, sensitivity to light, and central–peripheral integration disturbances); entoptic phenomena (such as “floaters”); and anterior segment (such as tear-related). In this study, 24.7% of patients had reduced or stopped driving because of eye problems compared with only 3% of controls. In the second study (Journal of the American Optometry Association, 1994), all 25 ME/CFS patients reported eye symptoms; the most common clinical findings were abnormalities of the pre-ocular tear film and ocular surface (19 patients), reduced accommodation for age (18 patients) and dry eyes (9 patients).
Later in the decade, two more reports appeared, both in the same volume of the Journal of Behavioural Optometry in 1997. One presented three in-depth cases for an audience consisting largely of practising optometrists, concluding that ME/CFS patients can experience symptoms ranging from mild accommodation dysfunction to debilitating disability. The other report reviewed the visual and ocular signs and symptoms of 141 patients, and discussed several management options including yoked prisms, progressive lenses, tints and ocular lubrication.
Then, between 2000 and 2010, two further reports appeared. The first was a case–control study (Annals of Ophthalmology, 2000) in which the 37 patients had significant eye impairments compared with controls; the impairments included foggy/shadowed vision and sensitivity to light, as well as problems of eyeball movement (oculomotor impairments) or tear deficiency. The second, from Russia (Vestnik Oftalmologii, 2003), reported vascular pathology of the eye in 70.2% of the 218 ME/CFS patients, and “dystrophic pathology” in 52.8%.
The astounding thing is that these six smallish reviews and studies (probably) represent the sum total of observations on, or research into visual dysfunction in ME/CFS in the past 30 years, even though eye symptoms are a concern for a majority of patients. As we have said before, time marches on but sometimes it can seem to stand very still indeed where research into ME/CFS is concerned!