Iris sphincter muscle Iris sphincter muscle The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris. It encircles the pupil of the iris, appropriate to its function as a constrictor of the pupil. It is found in vertebrates and some cephalopods. Initially, all the myocytes are of the smooth muscle type but, later in life, most cells are of the striated muscle type. Its dimensions are about 0.75 mm wide by 0.15 mm thick. In humans, it functions to constrict the pupil in bright light (pupillary light
There Is a Light That Never Goes Out home") is quoted in the song. According to Goddard, an earlier version lacked some of the finished version's ambiguity, culminating in the line "There is a light "in your eyes" and it never goes out". Due to a dispute between the Smiths and its record label Rough Trade Records after the group completed "The Queen Is Dead", nine months passed after the release of "The Boy with the Thorn in His Side" before the group issued another single. Once the matter was resolved, Rough Trade owner Geoff Travis felt that "There Is a Light That Never Goes Out" should be