One of the first things a parent teaches a child is common sense: never look directly at the sun.
Good advice, as staring at that ball of gas in the sky is a good way to fry your retinas. Fortunately, doing so is extremely painful, so most people look away before experiencing serious eye damage. Doctors nonetheless warn of the potential dangers on August 21, when millions across the United States gaze skyward to observe the total solar eclipse.
Without the proper eclipse glasses or solar filters, viewing the event can be risky, said Dr. Charles Slonim, an ophthalmologist at Tampa General Hospital and the USF Health Morsani College of Medicine.
“In a total eclipse, you can look at it because you’ll only see the outside edge of the sun,’’ he said. “But in Florida we’re only having a partial eclipse, so if you look at the sun (unaided) it can damage the eyes.’’
The path of totality – where the moon’s shadow covers the disc of the sun – will traverse from Oregon to South Carolina in 93 minutes, plunging parts of 13 states into semi-darkness. Residents of Carbondale, Ill., will enjoy the best show, when the total eclipse is longest – 2 minutes, 42 seconds. People in Tampa Bay can enjoy the height of the partial eclipse at 2:49 p.m.
Looking at the sun without protection, even during a partial eclipse, can cause conditions known as photokeratitis and solar retinopathy. Respectively, these can lead to cataracts or damage to the macula – the central part of the retina that focuses images at the back of the eye.
“Essentially, you can overload and damage the photo receptors that accept colors and send messages to your brain,’’ Slonim said. “So if you damage them, you’ll possibly have a permanent blind spot in the center of your vision. It’s like having macular degeneration.’’
Depending on the length of exposure, the sun’s intense ultraviolent radiation damages cells, much like a sunburn on the skin. Typically, solar damage results in pain inside the eyes, blurred vision, altered color vision, and dark spots, according to the organization Prevent Blindness. The symptoms usually disappear in a few hours or days. A person would have to stare at the sun for up to a full minute to suffer permanent damage to the retina.
Here are some tips for safe viewing of the eclipse, from the National Aeronautics and Space Administration:
- A pinhole projection is the cheapest and safest way to view the Aug. 21 event. Poke a hole in a small piece of cardboard and allow the sunlight to pass through the hole and onto a sheet of paper. The eclipse will unfold like a silent movie.
- Don’t view the eclipse with sunglasses. Buy a pair of solar eclipse glasses with a label that says ISO, which stands for International Organization for Standardization, as well as the name of the manufacturer. These inexpensive, disposable glasses are designed to allow no more than 0.00032 percent of the sun’s light to pass through. They can be purchased online, at science museums or specialty stores. Don’t try to cut corners here; there have been widespread reports of fake eclipse glasses that don’t offer the same level of protection.
- If you normally wear eyeglasses, keep them on. Put your eclipse glasses on over them, or hold your handheld viewer in front of them.
- Always inspect your eclipse glasses; if scratched or damaged, discard them.
- Don’t look at the uneclipsed or partially eclipsed sun through an unfiltered camera, smartphone, telescope, binoculars, or other optical device.
Similarly, don’t look at the sun through a camera, a telescope, binoculars, or any other optical device even with your eclipse glasses or a hand-held solar viewer — the concentrated solar rays can damage the filter and possibly your eyes.