The hordes who will descend on Cornwall and Devon to see the total solar eclipse in August risk "cooking" their eyeballs, specialists have warned.

They say people who do not take adequate safety measures could severely damage their eyes without realising it.

Some home-made viewers could even lead to worse damage.

More than a million people are expected to crowd into the south-west corner of the UK to observe the rare event on 11 August.

It will be the first total eclipse to cross the UK since 1927 and will be the world's last this millennium. There will not be another visible in the UK until 2090.

Safety warnings

Michael Maunder is an author and photographer who has travelled the world to view solar eclipses.

He has called on people to heed safety warnings and to avoid home-made viewers such as smoked glass or photographic negatives.

These may not be able to block all the sun's harmful rays - which means infrared heat radiation could "cook the eyeball", he said.

"You could damage the eyeball without being aware it," he said.

He pointed to research published following a partial eclipse in the 1950s. This found that several hundred people suffered eyesight damage and problems, he said.

Professor John Parkinson, of Sheffield Hallam University, is an eclipse specialist. He said home-made viewers were "totally unacceptable".

He said: "Do not run the risk - your eyes are too precious.

"I just hope the numbers of people that do silly things is vanishingly small."

Recommended procedure

The recommended way to watch the eclipse is to use a small mirror to project the moon's movement across the sun onto a flat surface.

The Consortium of Local Education Authorities for the Provision of Science Services has provided schools around the country with safe viewing advice.

"Even with viewers we do not recommend people look constantly at the partial eclipse," said senior adviser John Tranter.

However, where the eclipse was total, it could be viewed safely for a short time without a viewer, he said.

Retired army officer Gage Williams is Cornwall's eclipse co-ordinator. He said low numbers of people were likely to sustain injuries - perhaps 200, depending on the weather.

The Royal Cornwall Hospitals Trust estimates that an extra 2,500 visitors could be treated during the eclipse period.