Characterising eye movement dysfunction in myalgic encephalomyelitis/chronic fatigue syndrome
People who suffer from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) often report that their eye movements are sluggish and that they have difficulties tracking moving objects. However, descriptions of these visual problems are based solely on patients’ self-reports of their subjective visual experiences, and there is a distinct lack of empirical evidence to objectively verify their claims. This paper presents the first experimental research to objectively examine eye movements in those suffering from ME/CFS.
Patients were assessed for ME/CFS symptoms and were compared to age, gender, and education matched controls for their ability to generate saccades and smooth pursuit eye movements.
Patients and controls exhibited similar error rates and saccade latencies (response times) on prosaccade and antisaccade tasks. Patients showed relatively intact ability to accurately fixate the target (prosaccades), but were impaired when required to focus accurately in a specific position opposite the target (antisaccades). Patients were most markedly impaired when required to direct their gaze as closely as possible to a smoothly moving target (smooth pursuit).
It is hypothesised that the effects of ME/CFS can be overcome briefly for completion of saccades, but that continuous pursuit activity (accurately tracking a moving object), even for a short time period, highlights dysfunctional eye movement behaviour in ME/CFS patients. Future smooth pursuit research may elucidate and improve diagnosis of ME/CFS.
KeywordsMyalgic encephalomyelitis (ME) Chronic fatigue syndrome (CFS) Eye movements Prosaccades Antisaccades Smooth pursuit
This research was funded by ME Research UK and the Irish ME Trust. We are extremely grateful to all our participants, especially those suffering from ME/CFS, for taking part in the study. We thank Professor Leonard Jason, DePaul University, Chicago for kindly providing us with the DePaul Symptom Questionnaire (DSQ).
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