What is (are) Dry Eye ?
Poor Tear Production Dry eye occurs when the eye does not produce tears properly, or when the tears are of poor quality and dry up quickly. The eyes need tears for overall eye health and clear vision. Dry eye can last a short time or it can be an ongoing condition. It can include a variety of symptoms, such as discomfort and pain. Your eyes may sting and burn and you may have redness and a sandy or gritty feeling, as if something is in your eye. You may have blurry vision and your eyes may feel tired. Having dry eyes can make it harder to do some activities, such as using a computer or reading for a long period of time, and it can make it hard to be in dry places, such as on an airplane.  Tears and Eye Health Tears are necessary for overall eye health and clear vision. The eye constantly makes tears to bathe, nourish, and protect the cornea. The cornea is the clear, dome-shaped outer surface that covers the eye in front of the iris, which is the colored part of the eye. The eye also makes tears in response to emergencies, such as a particle of dust in the eye, an infection or irritation of the eye, or an onset of strong emotions. Tears keep the eye moist, and wash away dust and debris. They also help protect the eye from infections. Tears are made of proteins (including growth factors), body salts, and vitamins that maintain the health of the eye surface and prevent infection.  Tear Components Tears have three major components. - an outer, oily, fat layer produced by the meibomian glands (located in the eyelids)  - a middle, watery, layer produced by the lacrimal glands (located just above the upper, outer corner of the eye)  - an inner, mucous layer produced by goblet cells (located within a thin clear layer which covers the white part of the eye and the inner surface of the eyelids called the conjunctiva). an outer, oily, fat layer produced by the meibomian glands (located in the eyelids) a middle, watery, layer produced by the lacrimal glands (located just above the upper, outer corner of the eye) an inner, mucous layer produced by goblet cells (located within a thin clear layer which covers the white part of the eye and the inner surface of the eyelids called the conjunctiva). When the lacrimal glands do not make enough tears, dry eye can result. Any disease process that changes the components of tears can make them unhealthy and result in dry eye. Type of Dry Eye There are two types of dry eye: aqueous tear-deficient dry eye and evaporative dry eye. Aqueous tear-deficient dry eye is a disorder in which the tear glands do not produce enough of the watery component of tears to maintain a healthy cornea. Evaporative dry eye may result from inflammation of the meibomian glands, located in the eyelids. These glands make the oily part of tears that slows evaporation and keeps the tears stable. Most people with dry eye will not have serious problems, but severe dry eye may lead to inflammation, ulcers, or scars on the cornea, and some loss of vision. Permanent loss of vision from dry eye is uncommon.