EYE experts at the Royal Bolton Hospital have assured patients they are not at risk of being infected with the human form of mad cow disease.

The reassurances have been issued following new evidence that surgical instruments used for certain eye operations could pose a risk of infection with variant Creutzfeldt-Jakob Disease.

New highly sensitive analysis shows that protein infected with vCJD exists in the retina and optic nerve of infected patients.

Scientists obtained tissue from the post mortem examinations on four patients who had the disease.

The discovery was made by a team from the Imperial College School of Medicine, London, and reported in medical journal The Lancet.

It could prompt the drawing up of new models of risk management to prevent the further spread of vCJD.

A spokesman for the Royal Bolton Hospital says they will not alter their policies until the Government issues further guidance.

He said: "The study highlighted a very small potential risk of transmission via surgical instruments.

"The sort of eye surgery falls into three main categories.

"The first involves removal of the eye and is infrequently carried out in Bolton.

"The second, retinal surgery, is carried out at the Royal Manchester Eye Hospital and we refer our patients there.

"The third involves the vitreous part of the eye and only a very few such procedures are carried out at Bolton's eye unit. In all of these, disposable instruments are already wherever possible.

"The hospital is now waiting for the Department of Health to issue new guidance concerning risk management.

"If the guidelines are changed, the hospital will act immediately."