The simple answer is that safety eyewear should be worn whenever you deal with chemicals that might injure your eyes. This includes all laboratory personnel who work on or around substances that could cause injury if they are not handled properly. There are three basic types of safety eyewear: protective, corrective, and optical. Protective eyewear covers both eyes and protects them from splashes, dust, and other potential hazards. It does this by using a shield design (such as those used by military personnel) or plastic or rubber guards attached to each eye cup. These shields come in a variety of shapes and sizes to fit different facial configurations. They can also be tinted or colored bright enough for night vision use. The advantage of protective eyewear is that it prevents particles from getting into your eyes. This type of eyewear should be worn for any activity where there is a risk of exposure to chemicals or other physical agents that could hurt your eyes. Corrective eyewear allows you to see clearly without interference from stray light or fogging up due to moisture in the air. It does this by correcting common visual problems associated with working in low light levels or outdoors during cold weather conditions.