The Contact Lens: A Lens Floating on the Tears

The first contact lenses were large scleral shells of glass or plastic that rested on the white of the eye and vaulted over the cornea. They pressed on the sclera, starved the cornea of tears and oxygen, and could be worn only for short times. Kevin M. Tuohy of Los Angeles, assignor to Solex Laboratories, filed US 2,510,438, *Contact Lens*, on 28 February 1948; it was granted 6 June 1950. His lens is smaller than the iris but larger than the widest pupil, so it rests on the cornea alone and never touches the sclera; and its inner curve is slightly flatter than the cornea, so it touches near the centre while tears flow under its edges. The plastic corneal lens made contact lenses practical to wear all day. This rung works out the vertex correction between spectacles and a contact lens, and the tear lens that Tuohy's flatter fit creates, and shows the vertex effect on the bench — without putting anything in an eye.