Intrastromal corneal ring segment
（重定向自Intacs）
An intrastromal corneal ring (also referred to as intracorneal ring, INTAC, Keraring, Ferrara ring, or corneal implant) is a small device implanted in the eye to correct vision. The procedure involves an ophthalmologist who makes a small incision in the cornea of the eye and inserts two crescent or semi-circular shaped ring segments between the layers of the corneal stroma, one on each side of the pupil. The embedding of the two rings in the cornea is intended to flatten the cornea and change the refraction of light passing through the cornea on its way into the eye.