Eye Safety During a Solar Eclipse

On April 8, 2024, an unusual event will occur. A total solar eclipse will cross the United States (weather permitting) passing over Texas, and traveling through Oklahoma, Arkansas, Missouri, Illinois, Kentucky, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire, and Maine.

It will be the last total solar eclipse visible from the contiguous United States until 2044! So, let’s get those peepers prepped for viewing.

Watching a solar eclipse is a memorable experience, but you must do it safely to prevent serious eye injury or even blindness.

While spectacular to observe, solar eclipses can cause permanent damage to your eyes if viewed improperly. Eye safety should always be the number one priority when viewing a solar eclipse. Looking at any solar eclipse can expose your eyes to the sun’s rays, which can cause temporary or permanent damage to the eye.

What is a Solar Eclipse?

In short, a solar eclipse is when the moon passes between the sun and Earth. But there are different types of solar eclipses.

A partial solar eclipse occurs when the moon blocks only some of the sun’s light. In most places, this process will take about 1 hour.

A total solar eclipse occurs when the moon blocks all of the sun’s light during passing. As the moon blocks the sun’s light, it casts a shadow or darkness on parts of the earth. To experience complete darkness during an eclipse, you have to be in the path of totality—where the moon’s shadow is creating a trail as the Earth rotates. This only lasts 1 to 2 minutes

An annular solar eclipse happens when the Moon passes between the Sun and Earth while it is near its farthest point from Earth. Because the Moon is farther away from Earth, it appears smaller than the Sun and does not completely cover the star – creating a “ring of fire” effect in the sky. The most recent annular solar eclipse took place on October 14, 2023.

A total solar eclipse is the only type of solar eclipse where viewers can momentarily remove their eclipse glasses or viewers for a brief period of time when the Moon is completely blocking the Sun.

Partial or annular solar eclipses are different from total solar eclipses. There is no period of totality when the Moon completely blocks the Sun's bright face. Therefore, during partial or annular solar eclipses, it is never safe to look directly at the eclipse without proper eye protection.

How to Safely View a Solar Eclipse Directly

Staring at a solar eclipse without proper eye protection is dangerous and can cause irreversible damage, often called “eclipse blindness”, solar retinopathy, or retinal burns. The exposure can destroy cells in the retina that transmit what you see to the brain causing loss of vision and even blindness. This can take a few hours or even days to realize that damage has occurred. The retina does not have any pain receptors, so you may not feel any symptoms or pain. With that in mind, it is critical to properly protect your eyes when viewing an eclipse.

Please follow these rules:

Only view a solar eclipse through approved solar eclipse glasses or viewers. Purchase solar eclipse glasses that meet the international standard ISO 12312-2 for safe viewing. Visualeyes Optometry does not endorse any particular brand of solar viewers.

For proper use, stand still and cover your eyes with your eclipse glasses or solar viewer before looking up. After viewing, turn away and remove your glasses or viewer. Do not remove the solar eclipse glasses while looking at the sun.

If you normally wear eyeglasses, keep them on. Put your eclipse glasses on over them, or hold your handheld viewer in front of them.

Wear the solar eclipse glasses when looking at an eclipse, even when it is dark or dim outside.

Always read and follow all directions that come with the solar filter or eclipse glasses.

Inspect your eclipse glasses or handheld viewer before use. If they are torn, scratched, or otherwise damaged in any way, discard them.

Sunglasses (no matter how dark), smoked glass, unfiltered telescopes or magnifiers, homemade filters, and polarizing filters are not safe for viewing a solar eclipse.

Do NOT look at the sun through a camera lens, telescope, binoculars, or any other optical device while wearing eclipse glasses or using a handheld solar viewer. The concentrated solar rays will burn through the filter and cause serious eye injury.

Not everyone in a family or other group of observers needs their own eclipse glasses or handheld solar viewer. A partial solar eclipse, and the partial phases of a total solar eclipse eclipse, progress quite slowly. There is no point in watching continuously. If you instead take a brief glance every few minutes, the motion of the Moon across the Sun’s face will be readily apparent. There is plenty of time to share a small number of solar viewers among a large group.

Help and always supervise children to be sure they use handheld solar viewers and eclipse glasses correctly.

You can only view the eclipse directly without proper eye protection only within the path of totality when the Moon completely obscures the Sun’s bright face – during the brief and spectacular period known as totality. You will know it is safe when you can no longer see any part of the Sun through eclipse glasses or a solar viewer. Experience totality, then, as soon as a little bit of the bright Sun begins to reappear, replace your solar viewer to look at the remaining partial phases. Note that this applies only to viewing without optical aid (other than ordinary eyeglasses). Even during totality, do not view or image the Sun through camera lenses, binoculars, or telescopes. Outside the path of totality, and throughout a partial solar eclipse, there is no time when it is safe to look directly at the Sun without using a special-purpose solar filter that complies with the transmittance requirements of the ISO 12312-2 international standard.

When using telescopes, binoculars, camera lens, or other optics, special solar filters need to be attached to the front of the instrument.

How to Safely View a Solar Eclipse Indirectly

If you do not have eclipse glasses or a handheld solar viewer, you can use an indirect viewing method, which does not involve looking directly at the Sun.

A pinhole projector has a small opening (for example, a hole punched in an index card) or openings (for example, a colander or holes generated by placing your fingers perpendicular, slightly spread apart) that projects an image of the Sun onto a nearby surface.

For example, cross the outstretched, slightly open fingers of one hand over the outstretched, slightly open fingers of the other, creating a waffle pattern. With your back to the Sun, look at your hands’ shadow on the ground. The little spaces between your fingers will project a grid of small images on the ground, showing the Sun as a crescent during the partial phases of any solar eclipse. Or just look at the shadow of a leafy tree during a partial eclipse; you'll see the ground dappled with crescentshaped Suns projected by the tiny spaces between the leaves. A colander makes a terrific pinhole projector, as does a straw hat, a perforated spoon, or anything else with lots of small holes in it. Do not look at the Sun through the pinhole(s)!

You can also make your own eclipse projector using a cardboard box, a white sheet of paper, tape, scissors, and aluminum foil. With the Sun behind you, sunlight will stream through a pinhole punched into aluminum foil taped over a hole in one side of the box. During the partial phases of a solar eclipse, this will project a crescent Sun onto a white sheet of paper taped to the inside of the box. Look into the box through another hole cut into the box to see the projected image.

Symptoms from Incorrect Solar Eclipse Viewing

It can take a few hours to a few days after viewing the solar eclipse to realize the damage that has occurred.

Some common symptoms include: Loss of central vision, Distorted vision, and Altered color vision.

If you experience discomfort or vision problems following the eclipse, call Visualeyes Optometry to set up an emergency appointment. These problems should be considered urgent until any problems are ruled out. This is the best way to combat potentially severe complications, including vision loss.

Frequently Asked Questions

Do Eclipse Glasses & Handheld Viewers Expire?

If your eclipse glasses or viewers are compliant with the transmittance requirements of the ISO 12312-2 safety standard, and if the filters are not scratched, punctured, torn, coming loose from the frame, or otherwise damaged, you may reuse them indefinitely. Furthermore, you may look at the uneclipsed or partially eclipsed Sun through them for as long as you wish. Some glasses/viewers are printed with warnings stating that you should not look through them for more than 3 minutes at a time and that you should discard them if they are more than 3 years old. Such warnings are outdated and do not apply to eclipse viewers compliant with the ISO 12312-2 standard and in excellent condition. Make sure you get (or got) ISO compliant eclipse glasses or viewers. o To maintain your solar viewers in excellent condition, store them at room temperature, either in the case or package they came in or in an envelope or other container that will keep them clean and dry and protect them against scratches and punctures.

Is It Safe to Clean Eclipse Glasses and Handheld Solar Viewers?

Manufacturers of hard plastic eclipse glasses often supply a microfiber pouch that you may use to wipe the lenses clean. The same pouch may be used on the lenses of cardboard eclipse glasses and handheld solar viewers. You may also wipe them clean with any soft, nonabrasive tissue or cloth; Kimwipes are also suitable, but baby wipes and other wet wipes are not suitable. Cardboard must be kept dry; if it gets wet, it will swell and likely detach from the lenses. Do not use water, glass cleaner, or any other solvents or liquids to clean cardboard eclipse glasses and handheld solar viewers.

Are Welding Filters Safe for Solar Viewing?

The ISO 12312-2 standard was based, in part, on decades of experience using welding filters for observing the Sun. A welding filter with a shade number of 12 or higher transmits a safely tiny percentage of the Sun's light across the spectrum, whether made of tempered glass or metal-coated polycarbonate. Most observers find the view through a shade 12 welding filter uncomfortably bright and the view through a shade 15 or higher-numbered welding filter unattractively dark. The "sweet spot" is shade 13 or 14, which best matches the view in purpose-made eclipse glasses and handheld solar viewers, except that the image is green rather than yelloworange or white. o You should not use adjustable and/or auto-darkening welding helmets or similar products to view the Sun. Many do not go as dark as shade 13 or 14, and even those that do post a grave risk to your eyesight, either because you accidentally adjust them to an unsafe setting or because they don't auto-darken fast enough when you look at the Sun with them.