||What is Dry Eye?
During blinking tears form a film which coats, protects and nourishes the eye surface. When the tear volume is reduced or the tear film is unstable, eyes can fill gritty, scratchy and irritated. Anything that reduces the normal amount of tears may result in dry eye. Dry eye has a variety of causes: Excessive evaporation: Poor tear production: Unstable tear film
The Tear Film
The tear film is a trilaminate structure, which protects the surface of the eye, helping to create a smooth optical surface so vision stays crisp, clear and undistorted. A healthy tear film consists of three layers with distinct and complementary functions lipid layer. Lipid Layeris composed of oils secreted by the meibomaian glands. This is the outermost layer of the tear film covering the aqueous phase and providing a hydrophobic barrier, which modulates tear evaporation and retains moisture. The lipid layer also protects the eye surface from contamation. Aqueous Layer is produced by the lacrymal gland it is the central component of the tear film and accounts for about 98% of tear volume. It consists mainly of water but also contains other substances such as proteins, which nourish the eye, and electrolytes. This layer also washes away irritants, keeping the eye healthy. It helps maintain optimum vision by promoting spreading of the tear film across the cornea. Mucin Layer is the inner and foundation layer of the tear film it anchors the film to the cornea. It is produced from goblet cells within the conjunctiva. Its key functions are to facilitate film distribution evenly over the corneal surface and adherence to the corneal epithelium.