In Spain, the recent solar eclipse has raised concerns among ophthalmologists about eye injuries that appear after a delay. Looking at the Sun can damage the retina during exposure, though symptoms may not become apparent for hours. Retinal tissue has no pain receptors, so the injury is typically painless at the time. People may not immediately connect later vision problems to eclipse exposure.
Specialists such as Jesús Merayo, director of the Instituto Universitario Fernández-Vega, say no established treatment reliably reverses retinal damage caused by solar radiation. Prevention remains the basic protection: use eclipse glasses or a handheld solar viewer designed for solar observation and compliant with ISO 12312-2, or avoid direct viewing. Lucía Galletero, an ophthalmologist at Vithas Vitoria, says symptoms of solar retinopathy typically emerge within 12 to 28 hours after exposure. Blurred vision or a small basic dark or blurry spot may appear first. Straight lines can look distorted, and color perception may change. Light sensitivity can develop, along with difficulty reading or seeing fine details.
Anyone who develops these symptoms after an eclipse should seek prompt evaluation by an ophthalmologist. A dilated retinal examination can document macular injury and provide a baseline for monitoring, even when the visual defect seems subtle. Some injuries may be irreversible, and early assessment does not guarantee recovery. It can, but, help identify the damage and distinguish it from other causes of sudden visual changes. Recovery varies; severe solar-retinal damage can persist permanently.
Solar radiation remains dangerous even when the Moon partially obscures the Sun. During an eclipse, the cornea and lens focus sunlight onto the macula, the retinal area responsible for sharp basic vision. Concentrated light can cause thermal and photochemical injury to light-sensitive cells, resulting in solar retinopathy. Because the injury is painless, a small basic blind spot may be easy to overlook at first. Reading difficulty or distorted lines can be among the first noticeable signs. Ordinary sunglasses do not provide adequate protection.
During every partial phase, observers must keep eclipse glasses on or use a handheld solar viewer compliant with ISO 12312-2; even a visible crescent of the Sun can cause damage. In a total eclipse, unfiltered viewing is safe only during the brief period when the Moon completely covers the bright solar disk. Replace the filter before the bright photosphere reappears. Cameras and binoculars require a purpose-built solar filter secured over the front aperture; telescopes need the same protection. Eclipse glasses worn by the observer are not a substitute. For more on the strict safety measures recommended during eclipses in Spain, see the analysis of why removing eclipse glasses too soon can cause lasting eye damage.
Solar retinopathy is a documented risk during astronomical events, but public awareness remains limited. In Spain, authorities and medical associations regularly issue warnings ahead of eclipses, yet eye injuries still occur. To view the Sun directly, use a reliably sourced, undamaged viewer with clear instructions and an ISO 12312-2-compliant filter. Ordinary sunglasses and smoked glass are unsafe substitutes. Photographic film and radiographs are unsafe too, as are CDs. NASA does not certify individual commercial brands of eclipse glasses; the standard applies to the filter, not to a NASA-approved brand. The safest approach is to follow certified protective measures and avoid viewing the Sun, directly or through optical equipment, without the appropriate solar filter.
