Eyes Also Need Sun Protection

The Physics of Light Rays

The sun provides us with light and warmth through different types of rays. Those visible to the human eye form what is known as the visible spectrum—essentially, all the colors we perceive in nature. From a physics standpoint, the color of an object is simply the light it reflects or emits. These visible rays are harmless and bring only visual pleasure.

However, ultraviolet (UV) and infrared rays are invisible to the human eye. Infrared rays, also called "heat rays," are the warmth that every object in nature emits. We feel them whenever we get close to a warm object. The sun is the biggest source of infrared radiation, which can penetrate the skin up to 3-4 mm and primarily warms the body. However, prolonged and uncontrolled exposure without protective measures can lead to surface burns.

Ultraviolet rays, on the other hand, penetrate deeper and are responsible for sunburn and redness if we expose ourselves to the sun without protective creams. These rays are absorbed directly by objects in nature and can cause significant damage. While most UV radiation (over 98%) should be absorbed by the Earth’s atmosphere, the depletion of the ozone layer has allowed more of these rays to reach the Earth's surface. This is why meteorologists frequently warn that the sun is stronger today than it was 20 years ago.

When Does Sun Exposure Become Dangerous?

Nature has provided us with natural protective barriers. Squinting creates a "shade" for the eyes against bright sunlight, while the eyelids protect the delicate cornea and prevent strong rays from reaching and damaging the retina. However, there are situations where these natural barriers are not enough.

Experts warn that sunlight is most dangerous between 10:00 AM and 2:00 PM—even on cloudy days. Diffused light passing through thin clouds is just as harmful and can irritate sensitive eyes. The same goes for light filtering through fabric umbrellas and hats, which provide shade but not adequate UV protection.

Be especially cautious near bodies of water, sandy dunes, or snowy peaks. These surfaces reflect up to 80% of harmful UV rays, which can intensify their damaging effect by directly entering the eyes.

But Don't Panic!

Not every sun exposure results in immediate damage. Harm typically occurs over time due to prolonged, uncontrolled UV exposure. The best protection is knowledge and the right preventive measures.

UV rays are classified into three types:

• UVC rays: The most dangerous but are completely absorbed by the atmosphere.
• UVB rays: Contribute to eye diseases such as photokeratitis (sunburn of the cornea), cataracts, and even rare forms of conjunctival cancer.
• UVA rays: Proven to damage the retina, though only a small fraction penetrates deep enough to do so.
  Studies suggest that UVB radiation is increasing due to climate change and ozone layer depletion, which may contribute to the rising incidence of cataracts.

Other possible risks include:

• Structural changes in the eyes, including pigmentation shifts from prolonged UVB exposure.
• Macular degeneration, a retinal disease affecting older adults.
• Photokeratitis, which manifests within 6-12 hours of intense sun exposure, causing tearing, redness, pain, and eyelid twitching.
• Though symptoms usually resolve in a few days, repeated exposure can weaken vision.
• Solar retinitis, caused by directly looking at the sun or during a solar eclipse, affecting younger people more due to their clearer, healthier eye lenses.
• Temporary blindness, where intense sunlight causes oxidative stress in the retina, leading to temporary swelling and minor hemorrhages. Though these effects typically fade, sensitive eyes may suffer long-term damage.

The Solution: Sunglasses

To enjoy the sun without risking eye damage, proper protection is essential. Wide-brimmed hats help, but high-quality sunglasses provide the best defense.

When choosing sunglasses, focus on the lenses. The darker they are, the less light they let through. However, UV protection is crucial.

Check for labels specifying the level of UV protection. For example:

UV 400: Blocks all rays up to 400 nanometers, covering both UVA and UVB rays.
98% UV protection: A high level of protection against harmful light.
Without proper UV filters, dark lenses can do more harm than good by causing the pupil to dilate and let in more harmful rays.

Other key factors:

• Tint percentage:
• Up to 20% tint: Blocks wind and debris but not sunlight.
• Up to 57% tint: Suitable for cloudy or partly cloudy days.
• 57-82% tint: Recommended for daily sun protection.
• 82-92% tint: Essential for vacations at the beach or in the mountains.
• Over 92% tint: Used for extreme environments like glaciers and deserts—unsuitable for driving.
• Lens size: Larger lenses provide greater protection by covering a bigger area.
• Frame style: Wide frames and side shields offer extra defense against UV rays.
• Polarized lenses: Reduce glare and enhance visual comfort.

Finally, always check for the CE mark, which guarantees compliance with European Union safety standards. This mark ensures that the glasses provide UV protection up to at least 380 nanometers. You can find it on the inner side of the frame.

By choosing high-quality sunglasses, you can enjoy the sun safely while keeping your eyes protected.