Abstract: A contact lens for an animal (such as an egg-laying hen) having a nictitating membrane. The contact lens has a curved central region adapted to be disposed over and spaced from the cornea when the contact lens is in place in the eye. The lens also includes a peripheral region, disposed about the central region and having a curvature opposite thereto (i.e., a "reverse curvature"), to fit snugly under the animal's outer eyelids to aid in retention. An annular surface portion of the peripheral region is adapted to contact and rest on an annular region of the eye tissue disposed radially outward of the region at which the nictitating membrane joins the eye tissue. The radius of curvature of the central region provides, along with the increased diameter of the outer annular surface portion, a chamber within which the nictitating membrane may move under the lens without interference from the lens.