Wilson RL, Paterson KB, Hutchinson CV
College of Medicine, Biological Sciences and Psychology, University of Leicester, UK.
The objective of this study was to determine vulnerability to pattern-related visual stress in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). A total of 20 ME/CFS patients and 20 matched (age, gender) controls were recruited to the study. Pattern-related visual stress was determined using the Pattern Glare Test. Participants viewed three patterns, the spatial frequencies (SF) of which were 0.3 (low-SF), 2.3 (mid-SF), and 9.4 (high-SF) cycles per degree (c/deg). They reported the number of distortions they experienced when viewing each pattern. ME/CFS patients exhibited significantly higher pattern glare scores than controls for the mid-SF pattern. Mid-high SF differences were also significantly higher in patients than controls. These findings provide evidence of altered visual perception in ME/CFS. Pattern-related visual stress may represent an identifiable clinical feature of ME/CFS that will prove useful in its diagnosis. However, further research is required to establish if these symptoms reflect ME/CFS-related changes in the functioning of sensory neural pathways.
This work was funded by ME Research UK. We are very grateful to our participants, particularly those with ME/CFS, for giving up their time to take part in the study.
Comment by ME Research UK
Problems with eyes and vision occur in around three-quarters of people with ME/CFS, yet these symptoms are rarely mentioned in the scientific literature or in formal reports on the illness (see the overview below). Since 2012, Dr Claire Hutchinson and colleagues at the Vision and Language Research Group, University of Leicester have been working to identify and quantify vision-related problems in the disease. The Leicester programme was initiated with funding from ME Research UK and the Irish ME Trust; to date, it has resulted in three robust scientific papers reporting a range of visual impairments. These have shown, first, that ME/CFS patients perform worse than matched controls across three specific aspects of vision (read report); second, that eye movement dysfunction is a prominent feature of the illness (read report); and, third, that vision-related symptoms (sensitivity to bright lights; problems focusing vision and/or attention; and eye pain) are a significant clinical feature, and that they are severe or very severe in more than 30% of the patients (read report).
In 2014, we gave additional funding to the team (pictured below) to investigate visual discomfort during reading, a common activity which is important for optimal quality of life but which many people with ME/CFS find difficult. The first short report from this project has just been published in the journal Perception
The research team aimed to determine whether ME/CFS patients experience “pattern-related visual stress”, a form of visual hypersensitivity to patterns (such as a page of words). This is also known as Meares-Irlen syndrome after the two researchers who first noticed a connection between reading difficulties and the “glare” of a white page. Typically, such visual stress causes distortions of print, including print that appears to jump, text swirling effects, and letters that can double, fade or blur. Pattern-related visual stress is associated with symptoms like difficulty focusing, poor depth perception, and reading-related headaches, all of which seem relatively common in ME/CFS. In fact, a scientific report from Australia in 2014 showed that people with ME/CFS had significantly more visual stress-like symptoms, such as print distortions or dislike of bright light, than healthy volunteers.
In the Leicester investigation, participants (20 ME/CFS patients and 20 controls matched for age and sex) undertook the standardised Pattern Glare Test, which required them to report the number of visual distortions experienced when looking at three repetitive striped patterns of different levels of detail (spatial frequencies of either 0.3, low-SF; 2.3, mid-SF; and 9.4, high-SF, cycles per degree). The basic findings were that few visual distortions were reported by either group at the low-SF pattern where distortion is relatively mild, while both groups reported distortions at the high-SF pattern where distortions are relatively extreme. It was in the mid-SF pattern that group differences were observed (p<0.001), indicating increased susceptibility to visual stress. Also, the differences in the pattern glare score between mid and high spatial frequencies were significantly higher in the patients than the controls. In effect, patients with ME/CFS were experiencing the kind of distortions in the mid-SF pattern that healthy people experience at the high SF pattern.
While these findings provide much-needed experimental evidence of visual impairments in ME/CFS and support patients’ own reports, the causes of the pattern-related visual stress remain unknown. The authors speculate that cortical abnormalities in the brain, including changes to sensory neural pathways, may be involved, based on observations of symptoms of pattern-related visual stress in other neurological illnesses, including stroke, and migraine (which has an association with a diagnosis of ME/CFS – see a recent study). If reduced inhibitory and/or increased excitatory neurotransmission in the visual cortex is implicated, as seems likely, it would chime with the hypothesis of abnormal neurotransmitter activity in ME/CFS (see a review).
This initial report adds to the growing body of experimental evidence that problems with eyes and vision are important factors in ME/CFS. As Dr Neil Abbot of ME Research UK said in Leicester University’s press release: “Most people with ME/CFS report a range of eye and vision-related symptoms that interfere with their everyday lives, yet there has been very little scientific investigation of the problem. Dr Claire Hutchinson and her team have previously confirmed the existence of eye movement difficulties in ME/CFS patients, and that symptoms, including eye pain, can be severe. Her new report in Perception extends these findings and raises the possibility that vision anomalies, including pattern-related visual stress, may come to have a diagnostic role in the disease.”
Vision and Language Research Group at Leicester
The Vision and Language Group is a multidisciplinary group of researchers working on key issues in vision, visual cognition and language comprehension. Researchers in the group use a range of techniques including psychophysics, electrophysiology, computational modeling and eye movement recording to study sensory and cognitive processing in the brain from the level of individual neurons to the behaviour of the organism as a whole.
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!