Eye Safety Guide
Understanding the risks of solar viewing and how to protect your vision during eclipses and everyday sun observation.
Looking at the Sun Can Cause Permanent Blindness
Even brief unprotected exposure to the Sun can cause irreversible damage to your retinas. This damage can occur without any pain—by the time you notice vision problems, the injury has already happened. Always use proper ISO 12312-2 certified solar viewers.
Why Looking at the Sun Is Dangerous
The Sun is extraordinarily bright—about 400,000 times brighter than a full moon. Your eyes are designed to collect and focus light, which is normally helpful. But when that light comes from an extremely intense source like the Sun, this focusing ability works against you.
When you look at the Sun, your eye's lens focuses sunlight onto your retina—the thin layer of light-sensitive cells at the back of your eye. This focused sunlight can literally burn the retinal tissue, much like a magnifying glass focusing sunlight can burn paper.
The dangerous part: Your retina has no pain receptors. You cannot feel the damage as it's happening. By the time you notice vision problems hours or days later, the injury has already occurred and may be permanent.
The Three Types of Damaging Radiation
Solar radiation that can harm your eyes falls into three categories, and all three must be blocked by proper solar viewers:
Visible Light (380-780nm)
This is the light you can see. When too intense, it overwhelms your photoreceptor cells and can cause photochemical damage—essentially bleaching and destroying the light-sensitive cells in your retina.
Ultraviolet Radiation (UV, 250-380nm)
UV radiation causes photochemical damage to the retina and can also damage the front structures of the eye (cornea, lens). While your eye naturally blocks some UV, the intensity from direct sun exposure exceeds what your eye can handle.
Infrared Radiation (IR, 780-1400nm)
IR radiation causes thermal damage—literally heating and burning the retinal tissue. You cannot see infrared light, so you won't know it's affecting you. This is why filters that only dim visible light are dangerous—they may look dark enough while still allowing harmful infrared to pass through.
Solar Retinopathy
Solar retinopathy is the medical term for retinal damage caused by looking at the Sun. It's sometimes called "eclipse blindness" because many cases occur during solar eclipses—not because eclipses are more dangerous, but because eclipses motivate people to look at the Sun who otherwise wouldn't.
Symptoms of Solar Retinopathy
Symptoms typically appear within hours to days after exposure and may include:
- Blurred Vision General haziness or difficulty focusing, especially in the affected area
- Central Blind Spot (Scotoma) A dark or blind spot in the center of your vision where the damage occurred
- Distorted Vision Straight lines appearing wavy or bent (metamorphopsia)
- Altered Color Perception Colors appearing different or "washed out" in the affected area
- Afterimages Persistent visual impression of the Sun that doesn't fade
- Sensitivity to Light Discomfort or pain in bright conditions (photophobia)
Prognosis and Recovery
The outcome of solar retinopathy varies significantly depending on the severity of exposure:
Mild cases: Some people recover fully or nearly fully over weeks to months as retinal cells repair themselves. Vision may return to normal or near-normal.
Moderate to severe cases: Permanent damage is possible. While the eye may heal somewhat, some degree of vision loss—particularly the central blind spot—may be permanent. There is currently no treatment that can restore damaged retinal cells.
Important: There is no cure for solar retinopathy. Once retinal cells are destroyed, they cannot regenerate. Treatment focuses on managing symptoms and allowing natural healing to occur where possible—but prevention is the only reliable protection.
When You Need Eye Protection
Understanding when protection is required—and when it isn't—is crucial for safe eclipse viewing.
Partial Eclipse Phases: Protection REQUIRED
During any partial eclipse phase—when even a sliver of the Sun's photosphere (bright surface) is visible—you must use proper solar filters. Even if 99% of the Sun is covered, the remaining 1% is still blindingly bright and dangerous.
Total Eclipse (Totality): No Protection Needed
During totality—and only during totality—when the Moon completely covers the Sun's photosphere, it is safe to look at the eclipse with your naked eyes. This is the only time you can safely observe the Sun's corona (outer atmosphere), which is visible as a beautiful pearly white halo around the darkened Moon.
Critical timing: Totality is brief—typically between 1 and 7 minutes depending on the eclipse. You must put your solar viewers back on before totality ends. The moment the first sliver of the Sun reappears (called "third contact" or the "diamond ring"), you need protection again.
Annular Eclipses: Protection ALWAYS Required
During an annular eclipse (the "ring of fire"), the Moon never completely covers the Sun. A ring of the Sun's photosphere remains visible throughout. You must use solar viewers throughout the entire annular eclipse—there is no safe moment to view without protection.
Everyday Sun Viewing
The Sun is equally dangerous on any normal day—not just during eclipses. If you want to observe the Sun (to view sunspots, for example), you need the same ISO 12312-2 certified protection. Never look directly at the Sun without proper filters, regardless of whether an eclipse is occurring.
Safe Solar Viewing Methods
There are only a few methods that are genuinely safe for direct solar viewing. All others should be avoided.
Safe Methods
- ISO 12312-2 certified solar eclipse glasses
- ISO 12312-2 certified handheld solar viewers
- Purpose-built solar telescope filters (front-mounted)
- Indirect projection methods (pinhole projectors)
NOT Safe
- Regular sunglasses (any darkness)
- Stacked sunglasses
- Smoked glass
- Camera film or negatives
- CDs or DVDs
- Camera/telescope without proper filter
- X-ray film
- Polarizing filters
ISO 12312-2 Solar Viewers
The gold standard for safe solar viewing is glasses or viewers that meet the ISO 12312-2 international safety standard. These filters reduce visible sunlight to safe levels (transmitting only about 0.00032% of visible light) while also blocking harmful UV and IR radiation.
When properly made, certified solar viewers make the Sun appear as a comfortable orange or white disk. You shouldn't see anything else through them except bright light sources—if you can see through them in normal indoor lighting, they may not be dark enough.
Before each use: Inspect your solar viewers for scratches, punctures, tears, or separation of the filter material from the frame. If damaged in any way, do not use them—even tiny holes can allow dangerous amounts of focused light to reach your eye.
Methods That Are NOT Safe
Many commonly suggested "filters" are dangerous because they may dim visible light enough to look comfortable while still allowing harmful UV and infrared radiation through. Others simply don't block enough light of any kind. None of these should ever be used:
"Sunglasses are safe if they're dark enough"
Even the darkest sunglasses only block 10-20% of light. Solar viewers block 99.997%+. No number of stacked sunglasses will provide adequate protection, and dark lenses actually make the danger worse by causing your pupils to dilate, letting in more harmful radiation.
"Smoked glass works—people used it for centuries"
Smoked glass provides inconsistent and inadequate protection. The darkness varies across the surface, and it doesn't properly block infrared radiation. Historically, many people who used smoked glass damaged their eyes—they just didn't publicize it.
"Old camera film or X-ray film makes a good filter"
The metallic silver in developed film does block some light, but not nearly enough. Modern films often don't even contain silver. X-ray films are designed to be transparent to certain wavelengths—exactly the opposite of what you need.
"CDs and DVDs can filter sunlight"
The reflective coating on discs reflects some light, but they are not designed as optical filters and provide inconsistent, inadequate protection. The data side vs. label side differ, and neither is safe.
"It's safe to look through a camera or telescope"
This is extremely dangerous. Cameras and telescopes concentrate light. Looking through an unfiltered camera viewfinder, telescope, or binoculars at the Sun can cause instant, severe eye damage—far worse than looking with the naked eye.
Only purpose-made solar filters are safe
ISO 12312-2 certified solar viewers are specifically designed and tested to block adequate amounts of visible, UV, and infrared light. There is no safe substitute. The cost of proper solar glasses is trivial compared to the risk of permanent vision loss.
Protecting Children
Children Require Extra Attention
Children are at higher risk for solar eye damage and require active supervision during eclipse viewing. Here's why and how to keep them safe:
Why Children Are More Vulnerable
Children's eye lenses are clearer than adults', allowing more light—including UV radiation—to reach the retina. Their eyes also have larger pupils. Combined with natural curiosity and less impulse control, children face elevated risk.
- Supervise actively. Don't just hand children solar glasses and assume they'll use them correctly. Watch them to ensure they keep the glasses on whenever looking toward the Sun.
- Practice beforehand. Let children try on the solar glasses before eclipse day. Make sure they understand they can only see the Sun through them—everything else will be dark.
- Ensure proper fit. Solar viewers should fit comfortably without gaps around the edges. For small children, consider handheld viewers that a parent can help position correctly.
- Consider alternatives. For very young children (under 3-4), pinhole projection or watching a livestream may be safer than trying to use solar viewers.
- Explain, don't just instruct. Children are more likely to follow safety rules if they understand why. Explain that the Sun is so bright it can hurt their eyes, and the special glasses protect them.
- Model correct behavior. Children learn by watching. Use your own solar viewers correctly and consistently.
Alternative Viewing Methods
If you don't have ISO 12312-2 certified solar viewers, or if you want a safe option for large groups or young children, indirect viewing methods allow you to experience an eclipse without looking at the Sun at all.
Pinhole Projector
Poke a small hole in a piece of cardboard. Hold it up to the Sun and let light pass through the hole onto a second surface (another piece of paper, the ground). You'll see a small projected image of the Sun showing the eclipse in progress. Look at the projection, not through the hole at the Sun.
Colander or Strainer
A kitchen colander creates multiple pinhole projections. Hold it so sunlight passes through the holes onto a flat surface. Each hole will project a small image of the eclipsed Sun—dozens of little crescents during a partial eclipse.
Natural Pinholes
The gaps between leaves in trees create natural pinhole projectors. During an eclipse, look at the shadows cast by trees—you may see hundreds of crescent Sun images on the ground.
Livestream
NASA, observatories, and media outlets broadcast eclipses live with professional equipment. This is the safest way to see close-up views of the Sun and is a good option for cloudy weather or if you can't obtain proper viewers.
Never look at the Sun through a pinhole. Pinhole projectors work by letting you look at a projected image—not by filtering the sunlight for direct viewing. Always keep your back to the Sun when using projection methods.
If You Think You've Damaged Your Eyes
What to Do If You Suspect Solar Retinopathy
If you looked at the Sun without proper protection and are experiencing any vision changes, take these steps:
- 1 Stop any further exposure immediately. Do not look at the Sun again, even with solar viewers, until you've been evaluated.
- 2 Note your symptoms. Write down what you're experiencing—blurred vision, blind spots, distortion, color changes, sensitivity to light. Note when symptoms started and whether they're changing.
- 3 See an eye care professional. Contact an ophthalmologist or optometrist. Explain that you may have solar retinopathy. They can examine your retina and document any damage.
- 4 Don't panic, but don't delay. While there's no immediate treatment that can reverse the damage, proper diagnosis is important for monitoring and managing your condition.
Note: Mild afterimages that fade within a few minutes are normal after brief, incidental glances at bright light. The symptoms of solar retinopathy are more persistent and may not appear until hours after exposure. If symptoms persist beyond a few hours, seek evaluation.
Treatment and Prognosis
There is currently no proven medical treatment for solar retinopathy. Management typically involves:
Observation and monitoring: Your eye care provider will document the damage and monitor for changes over time. Some patients experience gradual improvement over weeks to months.
Supportive care: Your doctor may recommend wearing sunglasses and avoiding bright light if you're experiencing photosensitivity.
Low vision aids: For those with permanent central vision loss, magnifying devices and other assistive technologies may help with daily tasks.
The best treatment is prevention. There is no way to undo solar retinopathy once it occurs. Proper solar viewers cost just a few dollars—a trivial price compared to the possibility of permanent vision loss.
Protect Your Eyes
Only purchase eclipse glasses from verified manufacturers who meet ALL ISO 12312-2 requirements. Don't trust your vision to unverified sellers.
Find Verified Manufacturers