Abstract: A storage container or carrying case for contact lenses has a screw-on cap on which baskets for hanging the lenses vertically inside the canister are swingably suspended on a hinge plate which also holds the annular gasket for the cap closure when it is screwed down on the canister. A single helix thread on the outside of a tubular extension of the canister, for meshing with a similar internal thread on the rim of the cap, has a vertically running gap of a few degrees in width and a shallow channel is recessed in the flat flange surface just below the threading at the same orientation as the gap in the thread. The tightness of the closure is thereby readily adjustable to prevent leakage of a treating solution for the lenses from the closed canister in the event that it is knocked over while at the same time permitting escape of gas when the treating liquid includes hydrogen peroxide and a wafer is provided near the flat bottom of the canister to activate or modify the peroxide action.