We laughed at our father when we used to put on his sunglasses to chop onions, we laughed even loader when he started wearing his swimming goggles, however, he had a point. When onions are cut they release an enzyme called sulfoxide lyase and sulfuric compounds. When exposed to the air they react with each other to form a noxious vapour called thiopropanol sulfoxide. This is the vapour which irritates the eyes. It seems any barrier between the air borne particles and ones eyes will provide protection, albeit, limited in the case of our father's spectacles, or spectacularly impractical with the elasticated swimming goggles.
Roullier White's Onion Goggles are the perfect fit. They have a comfortable foam seal, anti fog lenses and the unisex design will fit most face shapes. They even come with a handy storage case with an easy release magnetic fastening.