It is known as dry eye when there is a shortage or lack of tears. The “dry eyes”, according to the severity of dry fall in light, medium and severe. Being currently the most common eye disease, because most are caused by irritable eyes, dry eyes.
What causes this?
First we must start by knowing who are the tears. The tear has three different fractions, which are produced in different glands: The lacrimal glands secrete the aqueous fraction, which constitutes 99% of the total tear. The conjunctiva, which lines the white of the eye and the posterior wall of the eyelids, is composed of cells that produce mucin Calciform, which constitutes only 0.5% of total tear. And in his eyelids have meibomian thickness (which occur when they are sick and styes chalazia) that produce fat in minute quantities. Each of these components are arranged as follows:
I. Mucin extends over the surface of the cornea, being the most posterior layer of the tear.
II. The aqueous tear mucin is placed on forming the middle layer.
III. The tear fat spreads as a thin film on the water, forming the outer layer.
The corneal surface is hydrophobic, ie, rejects the tear, as well as an area of fat repels water. The lid extends the mucin on the corneal surface and makes it hydrophilic, ie accepting the tear. On this surface mucin, which is renewed each blink, the tear extends watery, which is what kept moist and lubricates the ocular surface flicker. About the aqueous layer extends the lipid layer, as an oil slick spreads over the water. This prevents the water to evaporate easily tear and also facilitate the spread of water on the mucin layer.
A fourth type of dry eye, dry eye epiteliopático, which abound but the three factions tear, ill epithelium of the cornea, outer coat of the same, can not be spread by the mucin, thus rejecting the three components lacrimal . Some authors classify a fifth group of dry eye, dry eye for incongruity eyelid / eye, ie the eye where the eyelid deformities or paralysis suffers, and therefore not properly applied on the ocular surface, and therefore although production of the three components is normal lacrimal, eyelid, not extending over the eye.
What causes it?
As missing, tears, aqueous or oily mucin talking about dry eye acuodeficiente, mucodeficiency and lipodeficiency.
The cause may be one or more together, producing the dysfunction or destruction of several glands that produce tears. Less common causes of dry eye would be the corneal epithelial lesions, or eyelid abnormalities, deformities and paralysis. The most common is dry eye senile involution. As age increases a person, the eye produces fewer tears. Postmenopausal women suffer from dry eye far more often than boys their own age. During pregnancy or when taking birth control is also more common dry eye. Dry eye of postmenopausal accompanied by other droughts, affecting the lining of the nose, mouth and vagina, as this syndrome is known as type I. Sjögren More often than Sjögren’s syndrome is associated with systemic diseases such as rheumatoid arthritis or lupus erythematosus, and this association is called Sjogren’s syndrome type II.
There are many drugs that when taken for reasons extraocular do secrete fewer tears and saliva. These include anxiety (Valium), antidepressants, antipsychotics, antihistamines, anticholinergics (Buscopan, papaverine), antihypertensives, antiparkinsonian agents, diuretics, etc. If you stop taking the medication, is slowly recovering normal tear secretion. The marginal blepharitis, ie inflammation of the edge of the eyelids, is another common cause of dry eye. When the lid margins are inflamed, there is an abnormal or deficient secretion fat that protects the tear film evaporation, so the aqueous tear evaporates more value, and that contains dissolved salts become more concentrated, damaging corneal and conjunctival epithelium.
