Sample Eclipse Illustration

How to keep your eyes safe while viewing April’s solar eclipse

In a little more than a month, officials estimate around 300,000 people will come to Bloomington on April 8 to view the total eclipse, when the moon will completely cover the sun for approximately four minutes. However, medical experts are warning observers to take extra precautions when watching the eclipse.

Staying safe using eclipse viewers

Hin Cheung, a clinical assistant professor at the IU School of Optometry, said in an email it’s important that those viewing the eclipse do not look directly at the sun without a special solar filter until the sun is completely eclipsed by the moon. These filters are designed to filter out harmful levels of sunlight, ultraviolet radiation and infrared radiation, so those wearing them can safely look directly at the sun. Regular sunglasses, on the other hand, do not filter the necessary levels of radiation.

“We generally do not stare at the sun or have reasons to, so sunglasses are great for general use,” Cheung said. “However, with a solar eclipse, we suddenly have a reason to stare at the sun, and sunglasses are not made for the purpose of viewing the sun or eclipse directly.”

To see if your eclipse viewer has the proper level of protection, you can check the ISO number, which should say “ISO 12312-2.” The American Astronomical Society lists reputable vendors to purchase these eclipse viewers on its website. The Monroe County Library will also give away a limited number of free eclipse viewers starting March 11 at all its locations. The Bloomington Parks and Recreation Department is also selling eclipse viewers at City Hall and the Twin Lakes and Recreation Center.

If you do not have an eclipse viewer, Cheung said you can view the eclipse indirectly through a pinhole projector, where the sun enters a hole in an object and is projected out the other side of the hole. You can make a pinhole projector out of pieces of paper and foil following these instructions.

“With a pinhole projector, you never look directly at the sun, so you avoid the risk of solar retinopathy,” Cheung said. “Solar retinopathy is damage to your eyes from unsafe exposure to sunlight which can cause temporarily or even permanently damage to your eyes and vision.”


Why you shouldn’t directly watch the eclipse

Even if someone does not feel any immediate pain when looking directly at the sun without an eclipse viewer, the sun’s excessive radiation can still damage their eyes. Cheung said some common symptoms of this damage are blurry or distorted vision, or a blind spot in or near your central vision. These symptoms can be permanent or temporary.

“The retinal tissue inside the eye does not have pain receptors, so damage occurs without you feeling any pain at all, which makes this more dangerous,” Cheung said.

Cheung said that as you absorb excess UV radiation from the sun, reactive oxygen species — a type of reactive molecule that can damage other cells — accumulates in your eyes. Too much accumulation of this molecule can damage the eye’s photoreceptor cells, which convert light into signals sent to the brain.

“You can think of each photoreceptor cell like a pixel on your computer or TV screen,” Cheung said. “If the photoreceptor cell is damaged and dies, it is like having a blank or dark pixel in that spot in your vision. They do not regenerate or grow back.”

If someone experiences changes to their vision after viewing the eclipse, they should visit their local eye doctor, an optometrist or ophthalmologist, Cheung said.

IU’s Atwater Eye Care Center provides eye exams and care to patients in the Bloomington area, and you do not need to be an IU student or employee to receive this care. To make an appointment, call 812-855-8436.