Safety glasses are far from safe when the lenses are scratched. Scratched lenses make it hard to see, and although your eyes may be protected from falling or flying debris, the risk of slipping, tripping or falling increases as your ability to see decreases. If the lenses are not too damaged (no deep gouges) it is possible to repair them yourself.
Purchase a polymer eyeglass polishing kit. These can be found at most convenience and grocery stores. Relatively inexpensive, they are meant solely for light scratches, not deep gouges. Polymer polishing kits are meant solely for plastic lenses, such as those on inexpensive eyewear and safety glasses.
Read the directions on the box. Because every kit can differ slightly, reading the directions can prevent you from damaging your lenses even more.
Use the liquid inside the box to wipe or paint (often a brush applicator is included) over the scratches. Make sure all of the scratches are covered. Let the liquid dry for the recommended amount of time.
Use a small, soft cloth to wipe over the lens, smoothing any bumps made by the brush strokes. Your scratches should be eliminated.