There are a number of safety hazards associated with watching the upcoming solar eclipse on April 8.
“Watching an eclipse can be fun, but never look directly at the sun. You can seriously damage the retina and even be permanently blinded,” said Chantal Cousineau-Krieger, M.D., a staff ophthalmologist at the National Eye Institute’s Consult Service. The retina is the light-sensitive tissue in the back of the eye that sends signals to your brain, enabling vision.
The agency explains that the “sun emits high levels of ultraviolet (UV) radiation, which can cause damage to the cells of the eyes' surface and the back of the eye. In addition to UV radiation, the sun also emits infrared radiation, which can generate heat. Direct exposure to intense sunlight can cause thermal damage to the eyes, leading to inflammation, tissue damage, and discomfort.”
In an article on the topic, the institute explains the main risks associated with watching a solar eclipse (or looking directly at the sun any time) include:
Solar Retinopathy: a condition where the light-sensitive cells in the retina are damaged. This is caused by the sun's intense light, and it can result in a permanent loss of vision. Symptoms include blurred vision, sensitivity to light, dark spots or “blind spots” in your central vision, changes in color perception (or difficulty in distinguishing between colors), or a sensation of pressure in the eye.
It's important to note that the symptoms of solar retinopathy may not appear immediately after sun exposure and can develop gradually over hours or days. In some cases, the symptoms may resolve on their own, but in more severe cases, they may persist or worsen over time.
If you experience any of these symptoms after viewing a solar eclipse or being exposed to intense sunlight, it's essential to seek medical attention from an eye care professional promptly. Early diagnosis and treatment can help prevent further damage to the retina and preserve vision.
Photokeratitis: also known as "sunburned eyes" or "welder's flash," can occur from exposure to intense ultraviolet (UV) radiation from the sun. Symptoms may include pain, redness, tearing, and a feeling of sand in the eyes. While this condition is usually temporary, it can be quite uncomfortable. In some cases, photokeratitis may cause involuntary twitching or spasms of the eyelids (blepharospasm). These spasms may occur as a protective mechanism in response to eye irritation.
Repeated episodes of photokeratitis can increase the risk of long-term eye damage, including cataracts and pterygium, an abnormal growth of tissue on the conjunctiva (the clear membrane that covers the white of the eye) and the cornea (the clear front surface of the eye). If you experience symptoms of photokeratitis after exposure to UV light, it's essential to seek medical attention from an eye care professional for evaluation and treatment.
Macular Edema: Prolonged exposure to the sun, especially during an eclipse, can contribute to macular edema, a condition where the central part of the retina swells, leading to vision distortion and potential permanent damage.
Macular edema can reduce contrast sensitivity, making it challenging to distinguish between objects of similar colors or shades. Colors may appear less vibrant, and details may be harder to discern.
Symptoms of macular edema may also develop gradually over time, and some individuals may not experience noticeable symptoms until the condition progresses. If you experience any changes in your vision, especially central vision, it's essential to see an eye doctor to prevent further vision loss.
Therefore, a solar eclipse can be viewed safely by looking through special-purpose solar filters. These filters must meet an international standard, indicated by ISO 12312-2 certification. They must have the manufacturer’s name and address printed somewhere in the product, and not be older than three years or have any scratches on the lenses.
NASA offers these tips as well.
- View the sun through eclipse glasses or a hand held solar viewer during the part eclipse phases before and after totality.
- You can view the eclipse directly without proper eye protection only when the moon completely obscures the sun's bright face--during the brief and spectacular period known as totality. (You'll know it's safe when you can no longer see any part of the sun through eclipse glasses or a solar viewer.)
- As soon as you see even a little of the bright sun reappear after totality, immediately put your eclipse glasses back on or use a handheld solar viewer to look at the sun.