As people steps outdoors into the bright sunshine, their pupils automatically contract. Australian scientists are making use of how this "pupil reflex" is connected to the brain as a potential new way of testing the severity of multiple sclerosis (MS).

Scientists from the Australian Center of Excellence in Vision Science (ACEVS) based at the Australian National University (ANU) have used an instrument they are developing to accurately measure the pupil responses of MS patients and have found that the pupils of MS sufferers respond appreciably slower, the ANU said in a press release on Thursday.

The finding opens the door to a simple and quick way of tracking the severity of MS over time: the slower the response, the worse the MS.

"Our instrument uses special patterns of flashing lights that the patient looks at for four minutes," said Professor Ted Maddess, a vision scientist at ANU who is head of the ACEVS team.

"We use infrared cameras to measure light-induced changes in the diameters of both pupils, and with computer tracking we can measure the diameter to within a micrometer 30 times a second," he said.

"We have just published the results of our study of 85 MS patients, and we find that in MS patients the pupil response is about 25 milliseconds slower than in our control group. Although the study is preliminary, we believe the test has good potential in individual patients because it can precisely measure the speed of their response to within a millisecond."

Maddess said instead of an expensive MRI to track the condition, the new method gives an accurate readout after just a few minutes. That quick and easy test might, in the future, allow MS patients to be assessed on the spot and have their medication adjusted accordingly.

MS is a potentially devastating neurological condition affecting the myelin sheath of nerve fibres, leading to sensory disturbances and muscle weakness. Vision, speech, and walking are most often affected, and pain can occur. Puzzlingly, MS affects different people in different ways, but the condition inexorably gets worse with age and there is currently no cure. Some patients experience acute, inflammatory attacks while others don't.