Tactical sunglasses and goggles. ANSI Z87 safety rating for tactical use. For shooting sports or military use.

 ANSI rated frames and lenses are important to properly protect you from shrapnel, tree limbs, and other things that are out there in the "wild".  

Typically ANSI standard frames have 2mm polycarbonate lenses  *According to the recently updated American National Standards Institute (ANSI) Z87.1-2003 standard, protective Rx frames and lenses used for high impact must meet have the following:  Lenses must be marketed with the manufacturer’s monogram and a “+” mark to indicate they meet the high-impact testing standard.  All special tints and photochromic lenses require a marking as well.  Frames are tested with 2.0mm polycarbonate lenses to ensure they can withstand the impact from a 1/4-inch steel ball traveling at 150 fps without dislodging the lenses.  All parts of the frame are marked with Z87-2, indicating they have been tested to withstand high impact.  Again, legally anyone making the lenses has to make the lenses according to the ANSI standard marked on the frame which means 2.0mm lenses.  However, there are companies that don't follow the rules and will make them cheaply for you without the standard.  With some brands, this will void the warranty on the frame so look out for that.  If lenses are made properly to ANSI standards, they will have etching in them indicating the ANSI rating.  If you get the lenses somewhere else and they don't have the etching in the lenses, beware that theses lenses are not properly protecting you to the government standard. 

Sources:  "Socket it to Me"  20/20 Magazine