A drug used to treat MS has been found to limit vision loss, one of the most debilitating symptoms of the illness.
The drug natalizumab, or a placebo, was given to 2,138 MS sufferers from around the world every month over four years.
Participants were tested for visual loss every three months over the period.
The results, published in the journal Neurology, revealed that vision loss was reduced by 47 per cent in those taking natalizumab in comparison to those taking a placebo.
Laura Balcer, the study author, said: "Not only does natalizumab prevent the worsening of vision loss in people with relapsing MS, we also found the drug was associated with significant reductions in the likelihood of sustained vision loss.
"Specifically, this drug may have implications for preventing further sustained vision loss due to inflammatory demyelination of nerve fibres that connect to the eye, which is common in MS."
The drug has however, been associated with brain disease in several rare cases. Ms Balcer states that the benefits of the drug must be weighed against its risks.