Opaque tinting process for contact lens

The method of tinting a hydrogel contact lens such that the visual effect of the tint is not appreciably influenced or modified by the color of the wearer's eyes which comprises:

• (a) providing a tube-like structure which is closed at one end by structure which includes mask means and which is open at the other end;
• (b) orienting the tube-like structure in a first position with the open end upward;
• (c) adding a fluid column to the interior of said tube structure;
• (d) dropping the lens to be opaqued into the fluid in the tube, and permitting the lens to sink through the fluid column, so as to cause the lens to orient and center itself relative to the tube;
• (e) permitting the oriented and centered lens to come to rest on mask means defined in the tube bottom;
• (f) inserting a mandrel member into the tube and fluid to secure the lens in place between the mandrel and the mask structure;
• (g) opaquing the unmasked portion(s) of the lens with an opaquing medium which is a metal salt which undergoes reaction with a precipitating agent to provide a metallic opaquing material selected from the group consisting of silver, gold and platinum;
• (h) retaining the opaqued lens within the tube-like structure of step (a), or transferring the opaqued lens to another tube-like structure of step (a) in which case steps (b) and (f) are repeated;
• and,
• (i) tinting the opaqued, unmasked portion(s) of the lens wherein said tinting is carried out by exposing the opaqued portion(s) of said lens to a solution of a water-soluble leuco ester of a vat dye whereby said dye penetrates said opaqued portion(s) of the lens and thereafter the dye is oxidized to regenerate the vat dye.