Watching the eclipse without glasses: what happens to your eye

Solar retinopathy: a burn you cannot feel

The lens of your eye works like a magnifying glass: it focuses sunlight onto a tiny spot of the retina, the macula, which is exactly what you use to read, recognise faces and see detail. That concentrated energy damages the light-sensing cells.

The retina has no pain receptors. You can be harming it without feeling a thing.

Symptoms appear hours later

• Blurred central vision.
• A dark spot or “hole” where you look.
• Straight lines that look bent.
• Dull or altered colours.

Sometimes it improves over weeks or months; sometimes the damage is permanent. There is no treatment that reverses it. If you notice any of these symptoms after the eclipse, see an eye doctor.

Why an eclipse is more treacherous than a normal day

On a normal day the Sun dazzles you and you look away. During the partial phase, with much of the Sun covered, the light drops and you can stare longer without discomfort. But the sliver of Sun still visible is just as intense. That is why eye injuries spike during eclipses.

What does NOT protect you

• Sunglasses, however dark or polarised.
• Smoked glass, X-ray film, CDs, photo negatives or stacked sunglasses.
• Eclipse glasses that are scratched, punctured or not certified to ISO 12312-2.
• Eclipse glasses behind binoculars, a telescope or a camera viewfinder: concentrated light burns straight through.

How to watch safely

• Use glasses meeting ISO 12312-2, with no scratches or holes. With them on you should see nothing but the Sun.
• Put them on before looking up and take them off while looking away.
• Binoculars, telescope or camera: solar filter in front of the lens.
• With children: supervise them and check the glasses fit.
• No-look option: project the Sun with a projection viewer or a pinhole in a card.

The only exception: totality

Only inside the path, during the minutes when the Sun is completely covered, can you look without glasses: that is when you see the corona. The moment the first point of light returns (the diamond ring), glasses back on. Outside the path, even with 99% of the Sun covered, never take them off.

Sources

This content is for general information and does not replace an eye doctor. It is based on these sources:

• NASA — Eclipse Safety
• American Astronomical Society — fake eclipse glasses warning
• ISO 12312-2:2015 — Filters for direct observation of the sun
• Instituto Geográfico Nacional (IGN) — Recomendaciones prácticas

General information based on astronomical and ophthalmological organisations’ advice. It does not replace advice from a health professional.