An optical element has a substrate body made from transparent plastic and a coating having multiple layers. The coating includes a hard lacquer layer adjoining the substrate. The coating has a diffusivity ensuring the absorption of water molecules passing through the coating in the substrate and the release of water molecules from the substrate through the coating from an air atmosphere on that side of the coating facing away from the substrate with a flow density which, proceeding from the equilibrium state of the quantity of water molecules absorbed in the substrate in an air atmosphere at 23° C. and 50% relative humidity, brings the setting of the equilibrium state of the quantity of water molecules absorbed in the substrate in an air atmosphere at 40° C. and 95% relative humidity within an interval not more than 10 h longer than for setting this equilibrium under corresponding conditions with an identical uncoated substrate.