Solar eclipse: What happens to your eyes if you look directly at it – and why it’s even more dangerous than you think

Parts of the world are about to see one of the most stunning spectacles the sky can offer: a solar eclipse.

But that same sight can cause serious damage to people’s eyes – and it might be considerably more dangerous than you think. The danger is such that it might leave you unable to see anything again.

In the run-up to the solar eclipse, experts have urged people not to look directly at it. Instead, viewers are advised to wear special eclipse glasses – though they have sold out across much of the country – or pursue other methods, such as a colander.

It can however be tempting to look straight at the eclipse. Because the Sun is darker than usual, the usual instinctive reaction to look away from the light may not kick in, but that is exactly where the danger comes from.

The Sun is still incredibly bright, even when it is largely obscured by the Moon. And that intense light means that there is a danger that looking straight at it could cause lasting issues, including blindness.

What’s more, that damage might not be immediately obvious. Both the eye damage and the pain that results can take hours to become clear, so it might not be until hours after the eclipse that you realise you have done potentially permanent damage.

“One of the most common misconceptions is that a partial eclipse makes it safe to look at the sun. In reality, even during an eclipse, the sun remains bright enough to damage the delicate tissues of the eye,” said Alex Ionides, consultant ophthalmic surgeon at Moorfields Eye Hospital.

“The retina is the light-sensitive layer at the back of the eye that allows us to see. When you look directly at the sun, the bright light and ultraviolet radiation can damage retinal cells. This condition is known as solar retinopathy.

“Solar retinopathy can develop after only a short period of exposure. The damage may not be painful, so people often do not realise there is a problem until hours later.

“Symptoms can include blurred vision, distorted vision, reduced colour perception, difficulty reading, or a dark spot in the centre of vision. In some cases, the effects improve over time, but permanent vision loss can occur in some cases.

“Many people assume that ordinary sunglasses will protect their eyes. Properly accredited UV sunglasses are essential for everyday wear to protect your eyes from the sun’s harmful effects.

“Unfortunately, sunglasses do not provide sufficient protection against looking directly at the sun, particularly for prolonged periods.”

If someone does look at the Sun, and then develops symptoms, they should seek urgent medical attention, the hospital urged. Those symptoms include eye pain, redness, irritation, blurred or distorted vision, new dark spots in the eye or sudden changes in sight.

“While some people recover over weeks or months, others can be left with permanent visual impairment,” said Mohamed Elalfy, a consultant ophthalmologist who is president of the Royal College of Ophthalmologists.

After the last comparable solar eclipse, in 1999, at least 70 cases of eye damage were tracked by the College. Some are still living with the consequences decades after – including Peter Smith, from Taunton, who borrowed a welder’s mask that he thought would offer enough protection.

“Even now there is a residual impact. When I’m tired sometimes a flashing dot might come back, and it’s not nice when it does,” he told the BBC.

“If you’re going to go and watch it, make sure that everything you’ve got is correct.”

The same danger also applies to taking photos of the solar eclipse, which can damage the phone’s camera in much the same way. To keep the device safe, photographers are advised to use similar techniques, such as buying special filters that block out much of the light.