I recently saw a health show on TV that said you should wear darker sunglasses because they filter more light. Previously, I had heard that darker sunglasses cause the pupil to open wider and make the eyes more vulnerable to harmful light; ergo, you should wear lighter sunglasses with good UV protection. I have very light colored eyes, so my eyes are especially vulnerable to harmful light anyway, which is why I really want to get this right. Can you give me a definitive answer on this one?
— Blue-eyed and concerned
Dear Blue-eyed and concerned,
It's true that wearing darker lenses promotes pupil dilation. And, dilated pupils are quite vulnerable to damaging Ultraviolet (UV) radiation. So, darker shades — without adequate UV protection — could lead to eye damage. To prevent damage, it's important to select sunglasses with UV protection.
Your question raises an important point; sunglasses vary in their ability to block UV damage, but this variation is surprisingly not related to lens color or tint. Actually, a clear lens coating can protect the eyes from UV radiation. Both non-colored corrective lenses and colored sunglasses can be treated with this clear coating to provide up to 99 - 100 percent UV protection.
The U.S. government requires that all sunglasses sold in the U.S. block 99 percent of UVB radiation and 95 percent of UVA radiation — the two types of UV radiation that can damage eyes and cause disease. Still, be weary of glasses that claim to block UV rays without stating the specific level of blockage. The best UV protection is found in glasses that block 99 to 100 percent of UV rays. These protective glasses are clearly marked. Some sneaky manufacturers imply their glasses provide UV protection even though they aren't treated with the extra clear shield. This is because untreated plastic and glass blocks a small portion of UV rays, and some manufacturers' labels seem to stretch the truth. You might be especially skeptical of stylish, "knock-off" shades usually sold on the streets.
Luckily, you show savvy when it comes to taking care of your peepers. You're right about needing to be extra careful to protect your light (blue, green, or grey) eyes. People with light eyes are more vulnerable to UV damage than people with darker eyes. Your concern and know-how should lead you in the right direction as you continue to sort through the hype to pick some proper sunglasses.
Enjoy the sun!Alice!