Dr Claire Hutchinson, Dr Kevin Paterson and Dr John Maltby
Vision and Language Research Group, College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, UK
ME Research UK
Background and aim
People with ME/CFS report a range of eye and vision-related symptoms, including hypersensitivity to light, difficulty focusing on images, and slow eye movements. These problems often become a pervasive part of their condition, exacerbate other symptoms, and interfere with everyday tasks such as reading and driving. Despite this, there was little solid empirical evidence of visual difficulties in ME/CFS (see the overview below) until, in 2011, ME Research UK and the Irish ME Trust funded Dr Claire Hutchinson, Lecturer in Visual Neuroscience at the University of Leicester, to identify and quantify them.
Three robust scientific papers have now been published from this project, and these have shown that problems with eyes and vision are indeed a common feature of the illness. The most important findings are that ME/CFS patients perform worse than matched controls across three specific aspects of vision; that eye movement dysfunction is a prominent feature; and that most ME/CFS patients experience prominent symptoms, including eye pain (which is severe or very severe in one third of cases). Since these findings were published, two ophthalmic charities have stepped up to the plate with additional support for the blossoming research programme to include retinal imaging, and topics such as distance focusing and the perception of colour.
The research team now wishes to explore the effect of these visual impairments on everyday activities, and ME Research UK has supplied further funding to investigate visual discomfort during reading, a common activity which is important for optimal quality of life. The researchers will examine visual stress (discomfort experienced when looking at complex, repetitive patterns such as those present in text) and abnormal eye movements while focusing on text. Importantly, they will examine possible interventions to improve the reading experience, such as coloured overlays which may reduce visual discomfort and improve the experience of reading.
During the study, 50 patients and 50 age, gender, and education-matched controls will be recruited. Each will complete a series of standard outcome measures to assess diagnostic criteria, symptoms and quality of life. In the first series of experiments, non-invasive, infra-red eye-tracking methods will be used to estimate eye movements to and from targets while reading. Accuracy of eye targeting during reading (by manipulating word length), word frequency effect, perceptual span and binocular coordination will also be assessed. Further experiments will test reading performance by measuring reading acuity, critical print size and maximum reading speed from MNREAD Acuity Charts; and the effect of visual stress/glare patterns on reading ability. The final experiments will determine whether coloured filters overlaid on text have beneficial effects, with the effectiveness of each filter determined by the change in reading rate.
Problems with eyes and vision certainly seem to be a clinical feature of ME/CFS. Experimental evidence of difficulties with reading-related eye movements and/or glare may help raise awareness among healthcare professionals, including ophthalmologists, of the significant impact these symptoms have on patients’ quality of life.
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 over 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!