People who look at it carefully should see a small black circle drifting across the Sun.
Professor Sir Liam Donaldson said children are really vulnerable if they do try and get a closer look at what is happening.
Another top eye doctor Andrew Elliott, from the The Royal College of Ophthalmologists, said: "People
may be tempted to take `just one quick glimpse' through binoculars or a telescope so putting their sight at risk.
"But damage to the back of the eye can happen in an instant and once it has happened, there is no treatment."