The etiology of this disease is multifactorial and not clearly understood. CSK is usually a bilateral progressive condition, however the lesions are not usually symmetrical nor are they usually painful. Signs include pigmentation and vascularization of the cornea (extension of blood vessels onto the cornea). It is usually first seen at the lateral (temporal) limbus (the junction between the cornea and sclera), although it eventually can extend from any part of the limbus to cover the entire cornea. Severe cases can cause blindness. A diagnosis is usually established by ophthalmic examination of the eye.