Tasks of the tear film
- Humidification of the cornea
- Moistening of the conjunctiva
- Supply of oxygen
- Supply of nutrients
- Defense of bacteria and viruses through contained enzymes and antibodies
- Washing out dust and other foreign bodies
Composition of the tear film
The tear film is composed of a mucilaginous, an aqueous and a fatty part. The mucilaginous component is directly on the surface of the eye and its consistency compensates for small irregularities on the cornea and conjunctiva. In addition, it ensures that the otherwise water-repellent surface of the cornea becomes water-attracting, so that the adjacent aqueous part of the tear film can adhere to the cornea.
The aqueous component is the largest part of the tear film and contains enzymes, proteins and antibodies. The outermost, fatty component of the tear fluid prevents too much of the tear film from evaporating or running down the eyelid margin. The different parts of the tear film are formed in the large lacrimal gland below the outer eyebrow arch and in numerous small glands at the edge of the eyelid and the conjunctiva.
