The fluorescein test is an auxiliary test accompanying a eye examination and is performed using fluorescein dye. This yellow-green substance tints any damaged parts of corneal epithelial and areas where the contact lens adheres insufficiently to the eye. The fluorescein test is usually carried out during the slit-lamp examination where the coloring is visible under a special light. This test can detect mechanical damage to the cornea, corneal epithelial erosion, accumulated protein deposits on contact lenses and the contact lenses' improper adherence to the eye. After examination, fluorescein is spontaneously washed out from the eye with tears in a few minutes.