refraction defect due to irregularities of the surface of the cornea or lens
Keratoconus Keratoconus (KC) is a disorder of the eye which results in progressive thinning of the cornea.[3] This may result in blurry vision, double vision, nearsightedness, astigmatism, and light sensitivity.[3] Usually both eyes are affected.[3] In more severe cases a scarring or a circle may be seen within the cornea.[4]
Ciliary muscle The ciliary muscle /ˈsɪli.ɛəri/ is a ring of smooth muscle[2][3] in the eye's middle layer (vascular layer) that controls accommodation for viewing objects at varying distances and regulates the flow of aqueous humour into Schlemm's canal. It changes the shape of the lens within the eye, not the size of the pupil which is carried out by the sphincter pupillae muscle and dilator pupillae.[citation needed]