The drops are the first of their kind that avoid unpleasant side effects which deter up to a third of patients from continuing their treatment.

Up to half a million people in the UK suffer from glaucoma, which causes gradual loss of vision due to damage to the optic nerve.
It is most commonly treated with eye drops that reduce fluid pressure in the eye.

But until now these treatments have contained a detergent preservative that can cause severe side effects in some patients, including burning, itching, tears, or a ''dry eye'' sensation.

Many patients simply refuse to apply the drops because of the discomfort, thereby putting themselves at risk of vision loss.

Regular use of the eye drops can keep the condition under control for a patient's life time. Without them, a patient can go blind in five to 10 years.

When the disease becomes too advanced the only remedy is surgery, which is risky and may itself result in blindness.

The new treatment, tafluprost, contains none of the detergents that give rise to adverse reactions and is far more ''patient friendly'' than its predecessors.

Marketed under the brand name Saflutan, it is available in the UK from today and licensed for the reduction of elevated fluid pressure in the eye, or intraocular pressure (IOP).

Keith Martin, consultant ophthalmologist and glaucoma expert at Addenbrookes Hospital, Cambridge, said: ''Over 10% of people with glaucoma are at risk of blindness because they cannot tolerate current sight-saving eye drops containing harmful toxins including detergents.

''Today, for the first time, people in the UK will have access to a toxin-free sight-saving treatment that is powerful, well-tolerated and does not cause damage to the eye. This breakthrough is widely welcomed by the ophthalmology community.''

David Wright, chief executive of the International Glaucoma Association, called the development ''the greatest advance in glaucoma treatment of recent years''.

He added: ''The introduction of Saflutan is a particularly welcome addition to the range of these most powerful medications because its preservative-free formulation will allow those patients who are allergic to preservatives to benefit from control of IOP offered by this class of medication that was hitherto unavailable.''

Professor Ian Grierson, head of ophthalmology at the University of Liverpool, said: ''Given that compliance is a central issue for many people with glaucoma, tafluprost may help to reduce rates of discontinuation as it may be a much more comfortable treatment for these patients to use in the long term.''