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August 02, 2017

Can you really go blind by staring at the sun?

Infrequently Asked Questions: Why you shouldn't be looking at this month's solar eclipse

It's one of the first lessons we learn as kids, and one we happily accept as truth as the sun's rays blast our eyes. 

But what's actually happening in that eyelid-squinting moment--whether while driving or just enjoying time on the beach--that does our eyes so much harm? 

Curious, we reached out to Dr. John Dugan, a refractive surgeon for WillsEye Hospital, for an answer. 

  • The world is full of questions we all want answers to, but are either too embarrassed, time-crunched or intimidated to actually ask. With Infrequently Asked Questions, we set out to answer those shared curiosities. Have a question you want answered? Send an email to, and we’ll find an expert who can give you the answer you’re craving.

The meat of the question: Can you really go blind by looking directly at the sun? If so, how long would you have to be looking?

Yes. If you were forced to look at the sun, your eye acts like a magnifying glass and would focus the sun on your retina, creating a burn in the center of your vision ... It causes free radicals to develop and they then injure the tissues. The more exposure, the longer the exposure, the more potential damage there can be.

We do, instinctively, start to close our eyelids when our eyes even get close to looking at sunlight -- what's going on in the body that makes that happen so reflexively?

If you look directly at the sun you experience pain. This is what causes us to look away.

What kind of damage can the sun's rays do to our eyes? 

The infrared waves, or heat waves, cause thermal damage to the retina acutely. Long-term UV exposure has been shown to promote cataract formation.

How much protection does a pair of sunglasses typically offer? What should you look for when buying sunglasses, if you're concerned about UV rays? 

Sunglasses typically protect from UVA and UVB radiation by filtering these almost completely. Polarized lenses decrease overall spectrum reduction by limiting light to a given polarization

Are UV rays more of a concern during summer months? And how much should we still be paying attention to this sort of thing during winter months?

Because the angle of the sun and duration of sunlight is greater during the summer in the northern hemisphere, there is more UV light exposure during this season. People tend to spend more time outside in the summer and therefore it is a greater concern.

Are our eyes more susceptible to damage from the sun's rays as we get older?

No. Actually, as we develop cataracts, they tend to absorb more of the blue spectrum of light. Interestingly, almost all cataract implant lenses include UV light filters.

At what age do cataracts typically develop?

Usually around 50s and older. That’s when cataracts start to show up in people. Though sometimes children develop cataracts and you can develop them at a younger age.

What is some knowledge we now know about UV rays and shielding our eyes that we maybe didn't a decade ago? 

The most important thing we learned in the last few decades is that UV light is associated with cataract development.  This was determined by following a group of fishermen on the Chesapeake Bay. We have also learned that macular degeneration may be influenced by UV exposure.

Anything to add? Is there anything people should know?

A solar eclipse will be visible in the U.S. on Aug. 21. In Philadelphia, we will experience a partial eclipse of about 75 percent. A partial eclipse is more dangerous to view as the absence of the bright sunlight would allow one to stare at the sun. Unfortunately, the level of infrared radiation is still enough to burn your retina and cause a solar retinopathy ... No one should be staring at a partial eclipse.

Along those same lines, wouldn't looking at the sun setting--when brightness is down--also be bad?

When the sun is setting, it’s a bigger image because it’s being refracted by the atmosphere. Some of those light rays are being absorbed by the atmosphere more than they are during an eclipse, when they are high in the sky. When the sun is setting, it's’ getting bigger because it’s being refracted. And that's why it looks red--you’re not getting all the light. Some of the blue light and ultraviolet light is not coming to your eye.