Eye experts warn of damage from staring directly at solar eclipse
Thousands attend Adler Planetarium’s Eclipse Fest during the solar eclipse, Aug. 21, 2017.
Ashlee Rezin/Sun-Times file
When a patient complained to Dr. Jennifer Lim of blurry vision in August 2017, the ophthalmologist had a hunch the symptoms might have something to do with the eclipse that had occurred a few days earlier.
Lim asked the patient if they'd looked at the sun during the eclipse without protection. They confirmed Lim's suspicions, explaining that they thought it was safe because they were wearing sunglasses and the sun was partially obscured.
"That's not enough, unfortunately," said Lim, who works at University of Illinois Hospital in Chicago's Eye and Ear Infirmary and is the director of retina services at UI Health.
The person had suffered solar retinopathy, or retinal burns, which can occur within a few seconds of looking at the sun without protection, Lim said. The results are blurred vision, blind spots and even permanent vision loss.
With sky-gazers across North America gearing up for another solar eclipse on April 8, Lim and other eye experts advised observers to avoid the risk of long-term damage by wearing approved eclipse sunglasses.
The American Astronomical Society has a list of approved providers that sell eclipse watching glasses that are tested to meet safety standards, known as ISO 12312-2. These glasses contain filters many times darker than sunglasses that block nearly all light.
"Bottom line wear eye protection and make sure that that protection that you're using has a solar filter," Lim said, cautioning that a partial eclipse doesn't reduce the risk of damage.
Everyone outside of the eclipse's narrow path of totality — in which the moon appears to block 100% of the sun — will experience a partial eclipse next month, including in the Chicago area, starting around 12:50 p.m on April 8.
The North American path of totality begins over the Pacific coast of Mexico and then moves into Texas and 12 other states. One of those states is Illinois, but only the southern part of the state.
The only circumstance where it is safe to take a brief peek at the eclipse without aids is within the path of totality as the moon completely obscures the sun, revealing the sun's corona, or the outermost part of the sun's atmosphere. The corona is typically difficult to see because of the brightness of the sun's surface.
Downstate Carbondale was under the path of totality in 2017 and will be again in April. Several events are planned there ahead of the event.
At its peak, those not in the path of totality will look up to see — with proper eye protection — the moon blocking about 94% of the sun.
Observers who look at the sun without approved eye wear may not realize the damage they are experiencing — even when the sun is mostly blocked during a partial eclipse — because there are no pain receptors in the retina to alert about danger. Lim said symptoms may appear within hours of exposure
"What happens is the lens in your eye focuses all of that intense energy coming from the sun directly on your retina, much as it would any image and then that causes a photo-toxic reaction in the retina," Lim said. "So basically it puts a burn in your retina, and that burn occurs immediately."
Lim also cautioned against using the glasses with binoculars or phone cameras, as those devices can magnify the light and bypass the filters.
Dr. Manjot Gill, retina specialist at Northwestern Memorial Hospital, said dozens came in with vision issues after the 2017 eclipse. Most of those were false alarms, she said, but a handful did have symptoms that took weeks to clear up despite their injuries not being severe.
"Unfortunately, there's really no treatment. This can take several weeks to even months to clear up; this is not an overnight thing," Gill said. "In some cases the vision loss can be permanent."
The Adler Planetarium will hand out safe viewing glasses on the morning of the eclipse while supplies last. Pullman National Historical Park, 610 E. 11th St., will hold a viewing party from 1 to 3 p.m. on April 8.
Someone without proper eye wear can safely observe a partial eclipse with a pinhole viewer. Guides on how to make one can be found online. Another way is to use a colander to project the shadow of the eclipse onto a white background.
"It's wonderful that we have this opportunity, but we have to be able to do it safely," Gill said.