Solar eclipse: seconds without protection can burn retina

Solar eclipse: the risk of losing your sight in five seconds

How much is a minute of sky worth for a retina that cannot regenerate? This is not a rhetorical question. The total solar eclipse on August 12, 2026, arrives in Spain with a clear warning from ophthalmologists: looking directly at the sun for just a few seconds without protection can cause irreversible macular burns. And the first victim is rarely the ignorant, but rather those who trust regular sunglasses or eclipse glasses bought without proper criteria.

Why an eclipse deceives the eye

Physics is treacherous. During the partial phase, ambient light decreases, the pupil dilates, and the eye loses the discomfort reflex that normally forces us to look away on a sunny day. However, ultraviolet and infrared radiation still reaches the eye almost intact and concentrates on the macula. The result is a potentially permanent injury that takes hours to become noticeable. Some downplay the risk because in A Coruña, the area with the best visibility of totality, the sun will be only 12° above the horizon, almost like sunset. But physics does not care about gentle angles when the entire disk enters the retina.

Glasses that are a trap

Distrust towards "certified" glasses is not paranoia. CE and ISO markings are easily forged, and references to meaningless certificates are common. A home test circulating among amateur astronomers is decisive: wear the glasses indoors with the lights on. Through a genuine ISO 12312-2 filter, you should not see the window, your hand, or the light bulb. If you can see the room, they are decorative. Consumer authorities have withdrawn several models, including the LIONSTAR LSP1, for being darker than normal and creating the false sensation that totality has already begun. Ironically, glasses that are too dark are as dangerous as unfiltered ones.

No mirrors, no strainers: physics rules

Those who think a mirror offers protection are mistaken: it merely reflects radiation with the same intensity. Looking through a kitchen strainer is also unsafe, though confusion is common: the strainer must be placed with its back to the sun, and one observes the shadow projected on the ground where images appear. Welding glass, another classic option, is only valid from shade 14 upwards. Shades 12 and 13, found in standard face shields, are calculated for electric arcs, not the full solar disk; the scale is logarithmic, so a difference of two numbers is enormous.

The alternative: don't look and still enjoy it

The most sensible option is indirect viewing: observe the projection on cardboard or use tree shadows. Or simply do not look and wait for the thousands of images that will be published. Meanwhile, the eclipse has also become an organized social phenomenon: in Quintanarraya (Burgos), 800 enthusiasts will occupy the spaces of an improvised observatory equipped with a bar, restrooms, and Civil Guard presence to prevent chaos. Additionally, the TriEclipse Project is preparing to record animal reactions during the event, continuing with the eclipses of 2027 and 2028.

In short: the sky will offer a spectacle lasting only minutes, and the trinc day, eye emergency rooms will register their own surge. The difference is that spots in vision do not show up in photographs. Nor can they be fixed with Instagram filters.