Patients are first given anaesthetic drops to numb the eye. Doctors then use a tiny probe, which is as fine as human hair, to emit tightly-focused radio waves at specific points on the surface of the eye around the cornea.

The number of points can range from eight to 32 depending on the severity of long-sightedness.

This heat helps to slightly shrink the collagen in the eye. This in turn squeezes the cornea and steepens its curvature, correcting sight.

The technique can be used on both eyes to correct long-sight. But it can also be used on just one eye. This is particularly useful for people who need glasses to read.

They develop what is called "blended vision". They use one eye to read and the other to see in the distance.

The procedure is painless and patients can return to work or drive home that day. The improvements are almost instant.

The treatment was approved by authorities in the United States and European Union last year.

Studies in the US have shown it significantly improved the sight of nine out of 10 patients and half achieved perfect eyesight.