Final answer:
In cases of red eye, it is common practice to stain the cornea to identify any abrasions or foreign bodies, which assists in diagnosing conditions such as keratitis.
Step-by-step explanation:
When a patient has a red eye, it is a standard procedure to stain the cornea to assess for damages such as abrasions or foreign bodies. The cornea is the transparent layer on the front of the eye that, along with the iris, helps to control the amount of light entering the eye. Staining the cornea with fluorescein, a dye, can reveal corneal defects which are important to diagnose conditions like keratitis, an inflammation of the cornea which can be caused by infections, among other things. Conjunctivitis, commonly referred to as pinkeye, is the inflammation of the conjunctiva and also leads to redness in the eye, but involves different structures and is treated differently. Therefore, distinguishing between conjunctivitis and corneal issues is essential for accurate diagnosis and treatment.