Anorexia sufferers see things differently
In Summary
For the first time, Australian researchers have studied the eye movements of anorexia patients and discovered an unusual biomarker that could be used to diagnose anorexia with 95 per cent accuracy.
Anorexia Nervosa is a psychiatric illness that has a mortality rate among the highest of any mental illness, though the contributing factors involved in the cause remain unclear.
Based on literature linking psychiatric illnesses with abnormal eye movements, researchers from Swinburne University of Technology, University of Melbourne and St Vincent’s Hospital in Melbourne studied the eye movements of 24 female anorexia patients and compared them with 24 healthy individuals.
“Since the 1960s we’ve recognised that people with mental health disorders have problems with the way they move their eyes,” Professor Susan Rossell from Swinburne’s Brain and Psychological Sciences Research Centre said.
There is substantial evidence showing that people with anxiety disorders don’t move their eyes in the same way as healthy people. Of particular interest in psychiatric illnesses has been the examination of saccadic eye movements. These are rapid eye movements that abruptly change the point of fixation.
“When we look at an object we perform a saccade, a little eye movement between objects, in this way we scan the environment,” Professor Rossell said.
“What we found in this study was that when we tracked the eye movements of anorexia patients, they performed square wave jerks – their eye movements jerked between objects.”
Known as a saccadic intrusion, square wave jerks occur in only a small number of healthy individuals.
The aim of the study was to investigate whether individuals with anorexia and healthy control individuals differ in the rate of square wave jerks during attempted fixation.
The fixation task involved participants fixating on a white cross against a black background, which was presented on a screen in front of the participant. They were instructed to fixate for the entire duration for five minutes.
Eye-tracking was recorded using a remote view eye-tracker, showing participants with anorexia produced a significantly greater number of square wave jerks during attempted fixation than healthy individuals.
“This phenomenal finding tells us that it is part of a more fundamental brain network that is core to our eye movements,” Professor Rossell said.
“These findings clearly need to be replicated and expanded upon, but one speculation that can be made is that the neurotransmitter gamma-aminobutyric acid (GABA), which contributes to motor control, vision, and many other cortical functions, may be involved in these impaired eye movements.”
Medications that influence the GABA system have not previously been explored as a treatment avenue in anorexia.
The study was led by Melbourne University PhD student, Andrea Phillipou and recently published in Investigative Ophthalmology & Visual Science journal.