While wearing the glass, if you want to see what is behind you, then you have to turn your head for about 30 degrees for back side and then you could see that is reflecting inside the glass.
The outer 1.5-2cm of each lense is coated with a semi-transparent reflective layer. If the object behind you is well lit, you will see it in the reflective layer. If the object is not well lit, you will see through the reflective layer to whatever is in front of you.
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