Doctor's advice: Wear sunglasses when going out in summer

When it comes to sun protection in summer, most people focus solely on their skin, but overlook the eyes—an organ that is particularly prone to ageing.

Wearing sunglasses when out and about not only blocks out glaring sunlight, but more importantly, this habit also helps prevent a range of eye conditions. What harm can UV rays cause to the eyes? And how should different groups of people choose the right lenses for themselves? Let's find out.

4 Eye Conditions Caused by UV Rays

The cornea is the outermost layer of the eye. It is highly sensitive to ultraviolet (UV) light. While it protects the inner eye, prolonged UV exposure can damage it. This can cause photokeratitis (corneal inflammation). In severe cases, it leads to corneal clouding and vision loss.

Besides that, UV light can cause the following eye problems:

1. Cataracts

This mainly refers to age-related cataracts, the leading cause of blindness in older adults. UV exposure is a major trigger. Specifically, cortical cataracts are closely linked to UVB rays (wavelengths of 280-320 nm).

Key Facts:

  • Research shows that sunny regions have higher cataract rates and an earlier onset of the disease. For instance, Tibet has a much higher rate than inland China, and southern regions outpace the north.

  • Tropical and high-altitude areas see more cases because the eye's lens absorbs almost all UV light between 295-400 nm.

2. Macular Degeneration

This usually refers to age-related macular degeneration (AMD). It is the leading cause of irreversible vision loss in people over 60. Long-term light damage-from both UV rays and visible light—is a major cause.

  • The Risk: One study found that people who spend over 5 hours a day in the summer sun are twice as likely to develop AMD compared to those who spend less than 2 hours.

3. Pterygium (Surfer's Eye)

This is a growth of fleshy, vascular tissue that starts on the conjunctiva and spreads to the cornea. It affects appearance and can cause astigmatism, leading to blurry vision. It is triggered by wind, dust, and sunlight.

 • How it happens: Excessive UV exposure, wind, and dust cause non-infectious inflammation around the cornea. This triggers abnormal cell and blood vessel growth, forming a membrane.

4. Snow Blindness

This is an acute eye injury. It is typically caused by light reflection from welding, high altitudes, snow, or water.

 • How it happens: UV rays cause an acute photochemical injury to the cornea and conjunctiva. This damages eye proteins and destroys corneal epithelial cells. UV rays with a wavelength of 280 nm cause the most damage.

5 Lens Colors for Different Occasions

Many people choose sunglasses just for fashion. However, picking the right lens color is actually the first step to protecting your eyes. Dr. Wang Renyan, an ophthalmologist at Beijing Tsinghua Changgeng Hospital, shares the best choices for different scenarios:

Grey: Best for Glare Reduction

 • Benefits: Grey lenses offer moderate shade and reduce glare without changing true colors. They provide a clearer and more comfortable view, making them perfect for all weather conditions.

 • Note: Darker grey shades block more light.

 • Warning: Avoid wearing very dark lenses (like black) while driving. The sudden shift between bright and dark areas can delay your visual reaction, which is dangerous for road safety.

Brown: Best for the Outdoors

 • Benefits: Brown lenses block nearly 100% of UV rays, infrared rays, and most blue light. They boost color contrast and make everything look sharper. Their soft, soothing tint also helps reduce eye strain.

 • Best For: They are ideal for hiking, golfing, or driving. The American Academy of Ophthalmology also highly recommends brown sunglasses for water sports.

 • Tip: Amber or brown lenses are also great for older adults with weaker eyesight.

Green: Best for Reducing Eye Fatigue

 • Benefits: Green lenses offer excellent contrast. They balance colors well and filter out some blue light, which effectively reduces eye strain.

Yellow and Orange: Best for Foggy Days

 • Benefits: On overcast days, UV rays can still be strong. Yellow or orange lenses allow more light to pass through, which brightens your vision and enhances contrast.

 • Best For: Wearing them during dusk or foggy weather can significantly improve clarity while driving.

Red: Best for High-Glare Environments

 • Benefits: Red or rose-colored sunglasses greatly change how you see colors, but they significantly boost contrast. They are perfect for highly reflective environments like snowy ski slopes.

 •Warning: Because they cause color distortion, they are not recommended for designers or artists.

Tips for Choosing and Wearing Sunglasses

Thinking about buying a pair of sunglasses? Dr. Ning Weixia, an associate chief physician at Chengdu Second People's Hospital, warns that choosing the wrong pair offers zero protection. Here is a practical guide:

1.Buy from Professional Eyewear Stores

 •Choose certified retailers: Always buy from professional optical shops to ensure quality.

 •Consult a doctor: If you have eye conditions or vision problems, talk to an ophthalmologist first.

2.Tips for Nearsighted People: Go for Gray or Brown Lenses

According to Dr. Xia Qun, chief physician of ophthalmology at Beijing Hospital, people with myopia should keep these tips in mind:

Material matters: Resin lenses are your best option.
 •Pick the right shade: Avoid lenses that are too light (poor light filtering) or too dark (blurs vision). Gray and brown are the best choices.
 •Test them out: When trying them on, check for high clarity and make sure you don't feel dizzy.
 •Look for UV400: For maximum sun protection, UV400 sunglasses are the gold standard because they block 100% of UV rays.

3.Replace Your Sunglasses Every Two Years

 •They have an expiration date: Prolonged sun exposure degrades the lenses' UV protection. Wearing degraded lenses can damage your cornea and harm your vision.

 •The 2-year rule: A 2023 study confirmed that UV protection fades over time. If you wear your sunglasses for two hours a day, their UV protection will drop significantly after two years. It's best to replace them by then.

4.Wear Sunglasses Even with a Hat or Umbrella

Watch out for reflections: Parasols and sun hats only block direct sunlight. They cannot protect your eyes from the UV rays reflected off the ground.

Important Note: Sunglasses Are Not for Everyone

You should avoid wearing sunglasses if you have any of the following conditions:

 •Glaucoma (or a genetic predisposition to it, such as underdeveloped eyeballs)
 •Color blindness or night blindness
 •Optic neuritis or central serous chorioretinopathy (CSCR)
 •Preschool children (as their visual functions are still developing)