. . . "A composition which is preferred for coating a plastic lens contains a high concentration of water-dispersed colloidal silica, a trifunctional oranosilicon compound which is curable after hydrolysis and has the following formula, wherein R7 is an alkyl group having 1 to 4 carbon atoms and R8 is an alkylene group having 1 to 4 carbon atoms, and a curing agent." .