The perfect pair of sunglasses? Here's what really matters.

Recently, I was standing with my kids in front of a sunglasses display in a store. There were dozens of styles, various colors, lenses with different levels of tint, and prices ranging from a few euros to well over a hundred.

And suddenly I asked myself: How do you actually tell if a pair of sunglasses is good?

When buying sunglasses, most people focus primarily on whether they look good and fit comfortably. That’s important, of course. But when it comes to the health of your eyes, there’s another criterion that’s far more crucial: UV protection.

Many people believe that very dark lenses automatically provide better protection for the eyes. In fact, that’s not true. The tint of a pair of sunglasses says very little about their protection against UV radiation.

What matters most is that the sunglasses have a reliable UV filter. So when buying them, look for the “UV-400” label. These lenses filter out nearly all harmful UV radiation up to 400 nanometers, providing excellent protection for your eyes.

Why is this so important? While dark lenses do reduce visible light, At the same time, however, your pupils dilate. If there’s no UV filter, even more harmful radiation can reach your eyes than if you weren’t wearing sunglasses at all.

The tint of the lenses primarily affects visual comfort, not UV protection. For most everyday situations, medium- to dark-tinted lenses in categories 2 or 3 are ideal. Very dark lenses in Category 4, on the other hand, are intended for specific uses such as high mountains or glaciers and must not be used while driving.

And which lens color is best? In fact, it’s mainly a matter of personal preference. Gray, brown, or green lenses offer comparable UV protection when equipped with the same UV filter. They mainly differ in how naturally colors and contrasts are perceived.

Incidentally, price is not a reliable indicator of quality either. Expensive designer sunglasses do not automatically protect your eyes better than a significantly cheaper model. What matters is not the brand, but certified UV protection.

In addition to the UV filter, the size of the lenses also plays a role. The better your eyes are shielded from the front and the sides, the less stray light enters your eyes. This can be especially important when playing sports, in the mountains, or near water.

Children should also start wearing good sunglasses early on. Their eyes are even more sensitive to UV radiation than those of adults. Consistent protection is therefore particularly important when playing outdoors or on summer vacation.

My conclusion: When buying sunglasses, it’s worth taking a moment to look more closely. Even the most stylish pair is of little use if they lack UV protection.

So make sure they fit well, have lenses that are large enough, and—most importantly—are labeled “UV-400.” Your eyes will thank you for it for many years to come.