It’s not enough that the lacrimal glands make sufficient tears; equally important is the production of the right type of tears to keep the cornea nourished. The cornea lacks blood vessels so it depends on the tear film to keep it healthy and functioning optimally. The tear film has three layers: 1. Outer oily, lipid layer Produced by the meibomian glands located below the eyes. 2. Middle watery layer Produced by the lacrimal glands located above the eyes. 3. Innermost mucin layer Together with the lacrimal glands, the goblet cells of the conjunctiva (the outer lining of the sclera, or the white part of the eye) secrete mucin. Not only does it hydrate and lubricate the cornea, mucin also ensures that the cells of the eye surface don’t stick together when the eyes blink. Because the cornea is the eyes’ first layer to interact with the external environment, it is critical that it has its own defense system. The mucin layer wards off harmful organisms that may cause diseases. The rest of the tear components are made in the ciliary body just behind the iris (the colored part of the eye) and in front of the natural lens. They bring essential proteins, electrolytes, vitamins, and growth factors to the eye surface via the pupil, or the opening in the middle of the iris.