Millions of Britons watching Wednesday's solar eclipse must not use safety glasses kept from 1999 because degraded protection risks permanent eye damage, experts warned.
The event promises to be the largest solar spectacle visible from the UK in over 26 years. However, astronomers and eye care specialists warned that using old viewing equipment stored in drawers since the last major event could lead to irreversible vision loss.
Dr Greg Brown, an astronomer at the Royal Observatory Greenwich, told the Daily Mail that the protective film on older solar eclipse glasses can degrade over time. "So it is recommended to only use eclipse glasses manufactured with the last decade," Brown said, adding that viewers should strictly seek out glasses made to the ISO 12312-2 safety standard.
The Royal Observatory Greenwich, founded in 1675 in south-east London, serves as a national centre for astronomy and public science education. Its astronomers routinely publish guidance to ensure safe observation during major celestial events.
Eye damage risks and symptoms
Medical experts stressed that looking directly at the sun with the naked eye is dangerous at any point during an eclipse. Because solar radiation focuses directly onto delicate ocular tissue, viewing the event without verified protection causes severe burns to the retina.
Mohamed Elalfy, a consultant ophthalmologist and president of the Royal College of Ophthalmologists, warned that solar retinal damage occurs without initial discomfort. "Crucially, the retina has no pain receptors, so people will not feel the damage as it happens," Elalfy said.
"Symptoms may only become apparent several hours later and can include blurred vision, a central blind or dark spot, distorted vision, reduced colour perception and increased sensitivity to light," Elalfy added. "While some people recover over weeks or months, others can be left with permanent visual impairment."
The Royal College of Ophthalmologists is the professional body for eye doctors in the UK, setting clinical standards for ophthalmic care across the National Health Service.
How to check eclipse glasses safety
Optical specialists emphasized that viewers must inspect their protective gear carefully before looking at the sun. Equipment manufactured prior to 2015 used materials prone to physical deterioration and chemical degradation over time.
Kyla Black, Director of Optical Practice at Boots Opticians, urged buyers to examine new or existing glasses closely. "If you're purchasing specially made eclipse glasses, make sure to double-check that they are undamaged before use as even a glimpse of damage could have an impact on your eyesight," Black said.
To check an existing pair for scuffs or scratches, experts advise holding the glasses up and looking directly at the brightest light inside your home. If the protective layer is intact, no light should be visible through the lenses. Anyone uncertain about the safety of older glasses should obtain a new pair, which are cheaply available online or from institutions such as the Royal Observatory Greenwich.
Black also dispelled a widespread myth regarding everyday sunglasses. "It's a common myth that wearing multiple pairs of sunglasses can protect you from any harmful UV light," Black said. "This is untrue and should be avoided at all costs as only purpose-built eclipse glasses can allow you to watch an eclipse."
Best UK viewing locations and times
The eclipse will begin shortly after 18:00 BST on Wednesday, with exact start times depending on location. Observers will see the moon appear to take a bite out of the sun's right-hand corner before sliding over to cover most of the solar surface.
The deepest moment of the eclipse will occur roughly an hour after start time, around 19:00 BST, when parts of the UK will see up to 96 per cent of the sun vanish. After shrinking to a slim inverted crescent, the sun will re-emerge, with the eclipse ending shortly after 20:00 BST.
Data from Time and Date shows that Bishop Rock in the Isles of Scilly will experience the highest level of obscurity in the UK at 96.5 per cent. Elsewhere in the South West, coverage will reach 95.8 per cent in Penzance, 95.4 per cent in Falmouth, 94.6 per cent in Plymouth, and 94 per cent in Exeter.
Further north and east, Cardiff will see 93.2 per cent coverage, Bristol 92.9 per cent, Oxford 91.9 per cent, and Birmingham 91.8 per cent. London, Manchester, and Edinburgh will all observe roughly 91 per cent obscuration, while Inverness will see just over 90 per cent.
Although the UK will not witness a total eclipse, viewers across Northern Spain, Greenland, Iceland, and parts of the Atlantic Ocean will see the moon cover the sun completely.
Safe indirect viewing methods
For spectators who do not have certified eclipse glasses, scientists recommend indirect viewing techniques that project the sun onto another surface.
Dr Megan Argo, an astrophysicist at the University of Lancaster, explained that natural surroundings offer an easy way to watch the phenomenon safely. "The safest way for the public to enjoy the eclipse is to view it indirectly," Argo told the Daily Mail. "Standing beneath a leafy tree creates hundreds of tiny images of the Sun on the ground, which gradually change into crescents as the eclipse progresses."
Spectators can replicate this projection effect using everyday household items, such as a kitchen colander or a simple pinhole viewer crafted from a cardboard box.
"Projecting the Sun safely with a colander, a pinhole viewer or by using a tree canopy, will help people see the shape of the Sun's disk change as the Moon covers part of it for a couple of hours," Argo said.
