Children are especially vulnerable to eye damage from UV rays. The lens inside their eyes is still clear and their pupils are wider than in adults, which allows more damaging rays to reach the retina where visual images have to focus if we are to see them. Once the retina is damaged, visual impairment is likely to be permanent.

Here’s what to consider when choosing lenses that can protect your eyes from the hazards of UV overexposure.

All sunglasses, even those purchased at dollar stores, should now come with full (400 mm) UV protection, although more expensive lenses provide better visual clarity. The color of the lens does not matter, though light tints are not as effective for people whose eyes are very sensitive to bright light. If the label says UV 400, chances are it’s true or very close to it.

[Wirecutter’s recommendations for cheap sunglasses.]

Michael Stoff, the optician-proprietor at Eye Shoppe on 7 in Brooklyn, where I’ve bought all my new glasses, told me that the polycarbonate material of most sunglass lenses and lenses made of glass naturally blocks UV rays, but UV protection has to be added to plastic lenses. If in doubt about the UV protection afforded by your existing glasses, ask an optician who has a spectrometer to check them.

Ideally, both regular eyeglasses and sunglasses should have anti-reflective coatings on both sides of the lens, which is why I spent a little extra to get Crizal lenses that protect my eyes from UV light coming from behind me as well as from the front.

I also got photochromic lenses — best known in this country as the brand Transitions — in all glasses I might wear outdoors. They have excellent UV protection, Mr. Stoff said. When exposed to UV, even on hazy days, the lenses darken, then clear in a minute or so when you go indoors. The latest version of Transitions lenses, called Gen 8, released July 10, offer the best protection, he said.

However, photochromic lenses do not darken in a car because windshield glass blocks UV light. And they do not get as dark as dark-tinted sunglasses so may not work well enough for eyes very sensitive to sunlight. But if you wear contact lenses, you can now get photochromic contacts, marketed by Acuvue since March.