The scan, known as Optical Coherence Tomography (OCT), takes just a few minutes per eye and can be performed at a GPs surgery.  Multiple sclerosis is a disease that affects nerves in the brain and spinal cord, causing problems with muscle movement, balance and vision.

Around 8 out of 10 people with M.S. have a type known as relapsing remitting, which means people will have periods where symptoms are mild or disappear followed by flare-ups. After around 10 years half of patients will develop secondary progressive disease where symptoms get worse and there is little remission.

It is difficult for doctors to monitor M.S. because its course can be unpredictable. Scientists believe OCT could provide a good way to do this.

‘As more therapies are developed to slow the progression of MS, testing retinal thinning in the eyes may be helpful in evaluating how effective those therapies are,’ said study author Dr Peter Calabresi.

MRI shows multiple sclerosis in the brain: Disease causes inflammation

The team measured the eyes of 164 M.S patients, 59 of whom were showing no symptoms, every six months for around 21 months. They also gave them MRI brain scans once a year.

The study found that people with MS relapses had 42 per cent faster thinning than people with MS who had no relapses.

The MRI scans revealed people with MS who had signs of active inflammation – known as gadolinium-enhancing lesions – experienced 54 per cent faster thinning.

Meanwhile people whose level of disability worsened during the study experienced 37 per cent more thinning than those who had no changes in their level of disability.

The study was supported by the National Multiple Sclerosis Society, the National Eye Institute and Braxton Debbie Angela Dillon and Skip Donor Advisor Fund.