Medical LED Pen Light with Cobalt Blue for Ophthalmologists"Product description Main applications It can be used at following situations after corneal fluorescein staining. to check if corneal injury exists or not assess tear film stability (like tear film break up time ). to check if the corneal contact lens suit the patient. Be used in patients after being given corneal fluorescein staining who can't cooperate with the slit lamp biomicroscope check (like children or patients having special position,such as