In order to keep the eyes comfortable and vision as normal as possible, there is a thin film of tears that coast the eyes. This film of tears is made up of three different layers. The inner layer is a very thin film of mucus, which is produced by the conjunctiva. The next, or middle, layer, is the thickest. Essentially, this layer is a diluted solution comprised of salt water. This layer is mainly produced by the lacrimal glands, and serves mostly to keep the eye moist and keep out dirt and grit. Problems with this layer are the most common causes of dry eye. The outermost layer is made up of fats and oils, also known as lipids. The meibomian glands and Zeis glands serve to produce this layer.
Many people are affected by problems with this film. Those older than forty years of age are commonly affected, and there are thought to be as many as thirty million people in the United States who are suffering from this problem. The condition tends to be more commonly seen in women. There are several primary causes of this problem. Some obvious causes of dry eyes include excessive evaporation of tears, lowered production of tears, or an abnormality in the tear layer. A deficiency in the production of aqeous tears is normally found to be caused by excessive evaporation in the tear layer, or because of the stated lack of watery tears.
If the eye is not producing enough tears, this might have occurred as a result of the aging process, hormonal changes, or the presence of autoimmune diseases like Sjogren syndrome, lupus, or rheumatoid arthritis. The evaporation of the tear layer is normally put down to an insufficiency in the overlying layer. There are some kinds of medications that have also been found to cause problems in this regard. Some examples of this include beta blockers, antidepressants, antihistamines, and oral contraceptives.
An insufficiency in the lipid, or oily layer, is normally due to a dysfunction of the meibomian gland. Blepharitis is another potential cause of problems in this regard. This is essentially an infection of either the eyelashes or eyelids. This infection can result in a breakdown of the oil, thus leading to a deficiency in oil production. It is possible to treat all of these conditions at home, or at least to manage the potential onset of any of the problems mentioned here, but consultation with a medical professional is recommended.