can be worn over prescription glasses and contact lenses - if the user has his/her own eyeglasses, it may cause risk

worn over top of another pair of glasses
over prescription eyewear

http://blog.phillips-safety.com/what-safety-glasses-to-wear-...

The benefits of safety glasses are obvious and the importance of wearing them when performing any task that could possibly cause eye injury cannot be overstated. “But I already wear glasses,” some counter. “Won’t they protect me from harm?”

Wear Spectacles? Here are Some Safety Glasses You Can Wear Over Them
Not necessarily. For one, standard eyewear is not designed or rated for the impact resistance necessary to protect your eyes should you be hit by a flying piece of metal, a kicked-up stone, or any kind of airborne fragment. And glasses that shatter right next to the eye can turn one sharp projectile into many and easily be more harmful than wearing no protection at all.

There’s no denying it; only safety glasses are up to the task of keeping your eyes safe. For anyone requiring corrective eyewear and safety glasses, there are two options. One is to buy prescription safety glasses. For those who prefer their own glasses or want to avoid the expense of purchasing another pair of prescription lenses, “fitover” safety glasses are the answer. These universal-fit frames fit over most prescription frame shapes and sizes. Phillips Safety Products carries a trio of fitovers, available with clear, polarized gray, or contrast-enhancing yellow lenses and each one ANSI Z87-approved. Check out their highlights here:

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Note added at 1 hr (2016-06-23 18:35:44 GMT)
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I completed various safety courses and training in Tengiz, Kazakhstan.