The most common answer is ANSI Z87.1-2003 (also known as Z87.1+)-rated eyewear. This can vary from ballistics glasses, to tactical goggles, to paintball goggles. We also advice the even better military grade MIL-DTL-43511D!
Additionally, the player must decide if they want sealed eye protection (goggles), or wants to use ballistics glasses. This website in no way is responsible for a player's choice, but recommends for maximum safety to use goggles. Glasses are not recommended because it is possible for a bb to hit in an area not covered by the glasses. Also, be aware that certain fields require sealed eye protection whereas others may not. It is best to find out prior to attending a game at the particular location.
Some well known eyewear brands are WileyX, ESS, Bolle etc.