Rachel L. Wilson, Kevin B. Paterson, Victoria McGowan and Claire V. Hutchinson
Department of Neuroscience, Psychology and Behaviour, College of Life Sciences, University of Leicester, Leicester, UK
People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) report vision-related reading difficulty, although this has not been demonstrated objectively. Accordingly, we assessed reading speed and acuity, including crowded acuity and acuity for isolated words using standardized tests of reading and vision, in 27 ME/CFS patients and matched controls. We found that the ME/CFS group exhibited slower maximum reading speed, and had poorer crowded acuity than controls. Moreover, crowded acuity was significantly associated with maximum reading speed, indicating that patients who were more susceptible to visual crowding read more slowly. These findings suggest vision-related reading difficulty belongs to a class of measureable symptoms for ME/CFS patients.
This work was funded by an ME Research UK (Grant No. SC036942) to CH and KP. VM was supported by an Economic and Social Research Council (Grant No. ES/L010836/1).
Comment by ME Research UK
Many people with ME/CFS suffer from problems with their eyes and vision, such as oversensitivity to light, troubles with focusing, and dry eyes. Reading can therefore be challenging, particularly for long periods, and pattern glare, headaches and difficulty tracking lines of text are commonly reported. However, before now, the reading performance of ME/CFS patients had not been assessed objectively.
Over the last few years, Dr Claire Hutchinson and her colleagues at the University of Leicester have been looking in depth at some of the vision-related problems associated with ME/CFS, supported in part by grants from ME Research UK.
The group has found that most ME/CFS patients experience a degree of eye pain and sensitivity to bright lights. Using sophisticated eye-tracking techniques, they have also shown that patients struggle to focus on one object and ignore irrelevant information, are slow in shifting attention between objects, are slower than normal and less accurate in their eye movements, and are vulnerable to pattern-related visual stress.
In their latest ME Research UK-funded study, published in the journal Frontiers in Psychology, the Leicester team set out to evaluate what impact ME/CFS has on reading performance. A total of 27 ME/CFS patients and 27 healthy control subjects took part in the research; all had normal vision or corrected-to-normal vision (i.e. they wore spectacles or contact lenses) and none had any history of eye disease.
Reading performance was assessed using two standardised tests, the Minnesota Reading Acuity Chart and the Radner Rate of Reading Chart, which between them produced the following measures:
- Reading acuity (the smallest print size that can be read without significant mistakes),
- Maximum reading speed (not limited by print size),
- Average reading speed, and
- Critical print size (the smallest print size that can be read at maximum speed).
As expected, the maximum reading speed was significantly slower in ME/CFS patients than in control subjects, and patients also tended to have a slower average reading speed. However, reading acuity and critical print size were not different between the two groups, indicating that the reading difficulties were not due to an inability to make out smaller print.
Furthermore, ME/CFS patients and control subjects performed similarly on a vocabulary test, showing that the differences in reading performance between the two groups were unlikely to be due to cognitive problems.
The researchers also looked at uncrowded visual acuity for individual words and letters (identifying a word or letter on its own) and crowded visual acuity (identifying a target letter surrounded by other letters), using the logMar Crowded Test.
While uncrowded visual acuity appeared to be similar in patients and controls, ME/CFS patients did have greater problems with visual crowding and performed less well on that test. Furthermore, those individuals who were more susceptible to visual crowding were also shown to read more slowly.
These findings build on a considerable body of work from Dr Hutchinson and her team in which they have detailed and explored the vision-related symptoms associated with ME/CFS. While many people with he illness know full well how difficult it can be to read comfortably, particularly for long periods, this is the first time these problems have been assessed objectively in a laboratory setting.
As the researchers conclude, ‘identifying and treating vision-related symptoms of ME/CFS could provide a means of improving the everyday lives of patients’.