Certified safety glasses have to be tested to meet levels of eye, orbit and cheek coverage against splashes and also impact injuries. There are different levels of certification: low, medium and high impact certification.
The Australian safety certification code is 1336.7 for medium impact prescription safety glasses and 1337.1 for non-prescription.
The reason that low impact certification exists is for professions that do not have exposure to high velocity debris on a regular basis but do require eye protection. Some of these professions include nursing and medicine. The other differences include the size of the lens and the arms of the frame will not provide the same coverage as the medium impact safety frames. Also the lens material doesn’t have to withstand as high a velocity ballistic testing.
Medium impact is the highest rating you can achieve in safety glasses, the lenses are made up of polycarbonate or a trilogy type material. These materials are known to be bullet proof, when they are a certain lens thickness. These are the most commonly required safety glasses, for use in the work place. Due to their superior coverage and eye protection. Some of the industries that these are commonly used include: construction, mining, mechanical, manufacturing and landscaping, just to name a few.
All prescription safety glasses have to undergo a certification process, this is one of the reasons that these glasses take longer than standard glasses to manufacture. They generally take between 1 and 3 weeks to be made, depending on the laboratory used and lens type ordered.
High impact certification is achieved by wearing a full face shield over a pair of medium impact certified safety glasses.
Non-prescription or standard safety glasses for the most part are available with medium impact rating. There are a couple like the Eyres floating range that is only low impact due to the air pockets located in the frame so that it will float.
Please consider your tasks when choosing you eye protection and make sure that it is the best option for you. For example, if you work in a dusty environment then consider a goggle or a positive sealed pair of safety glasses. As this will decrease the amount of dust your eyes are exposed to.