Problems with eyes and vision are common in people with ME/CFS – yet there is very little formal evidence in the scientific literature that visual symptoms actually exist. 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 trying to identify and quantify vision-related problems in the disease.
The group published the first scientific paper on its findings several months ago – read our essay – and a second report has now appeared, specifically on eye movements. The experiments measured cognitive speed, and eye movement tracking during ‘smooth pursuit’ of a slowly moving object and during reflexive (prosaccade) and inhibitory (antisaccade) movements to visual targets on screen.
Although the ME/CFS patients and matched controls (20 in each group) were similar in many respects, patients generally performed worse than controls in tasks that required quick and accurate eye movements. In particular, the ability to perform eye movements opposite a target (antisaccades) was more impaired in ME/CFS patients than controls, particularly for positional errors. In addition, patients were deficient in their ability to track closely a moving target during ‘smooth pursuit’, and their performance deteriorated as the testing session went on, something not seen in the healthy people. As the authors point out, it may be that patients are susceptible to fatigue even at these very short timescales – the ‘smooth pursuit’ requires sustained musculature activity for 30 seconds, and the 3 test-runs take only 5–10 minutes.
Intriguingly, the visual deficits seemed to be related to age in the ME/CFS patients but not in the healthy people, suggesting that older adults with the illness are less able than young adults to compensate for ME/CFS-related vision deficits. In fact, the overall disease impact may be proportionately greater in older ME/CFS patients, as a recent ME Research UK-funded report has also suggested.
Reference: Characterising eye movement dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome. Badham S & Hutchinson C. Graefes Arch Clin Exp Ophthalmol 2013 ; Aug 6: Epub ahead of print
Image courtesy of: Patrick J. Lynch, medical illustrator, December 23, 2006