A maker of more than half a million recalled contact lenses blamed for reports of corneal tears and other injuries acknowledged Wednesday that some of its users may have experienced “severe eye pain.” Officials with CooperVision Inc. of Fairport, N.Y., urged wearers of Avaira Toric contact lenses who believe they’ve suffered harm to stop the using the products, which were first voluntarily recalled on Aug. 19 because of problems with residue left behind during manufacturing.