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.

1. Advantages and disadvantages
Advantages. More complete, athletes and comfort are among the aesthetic effect.
Contact lenses provide a number of advantages in the field of vision to be attached to the tear film. It represents also a more convenient option for those who practice sports or simply for anyone wishing to obtain a better aesthetic effect.

There are three main visual defects: nearsightedness, farsightedness and astigmatism. Some experts consider the fourth defect presbyopia or farsightedness, but it is a physiological defect that all persons actually suffering. Contact lenses can correct all these defects, regardless of the number of diopters you have.

Although the traditional glasses can correct these same defects, have a number of limitations that contact lenses do not have:
- Glasses modify the size of objects, alter the visual perception of reality (a myopic look smaller and a larger farsighted).
- The visual field is limited to the saddle.
- The glasses, over time, they gradually lose the natural shine of the eyes.

The major disadvantage of contact lenses has to do with running. The patient must be very scrupulous in maintaining the lens and will have to spend a few minutes a day to insert the lens, clean it and keep it in position.

2. Lens Types
According to visual impairment and eye conditions will be convenient different types of lenses. There are two main types of lenses:

- The hard lenses, which are small and rigid. The adjustment period is long but snap in and out more easily.
- Soft lenses, which are larger and more flexible. Its handling is more sensitive but are more comfortable and faster adaptation. Its use is restricted to myopia, hyperopia and astigmatism mild.

3. Who can wear them?
Previous study. You must always perform a complete analysis of the eyes.
You must always perform a preliminary analysis of the eye because the tear, eyelids and the cornea must meet certain requirements so they can tolerate contact lenses.

This analysis must ascertain what the eye, taking measurements of diameter and curvature of the cornea and check the behavior of light through the eye, the refraction.

Some people react to the presence of the lens. The watery eyes, sensitivity to light or physical discomfort may prevent their use. Young children and the elderly, for the skill and discipline required, people may not be suitable for contact lens wear.

4. Techniques to place
Placement. Maintain good eye open is essential to correctly position the lens.
The user must place the lens on your finger and bring it closer to the eye until very close to the tear film. Then, the lens itself has a tendency to adhere to and placed inside. At first you should use a mirror to help see the lens and the finger, until you have skill.

There are slight variations depending on the lens, as the soft tissues are more sensitive, but usually the patient ends up taking his unique way of placing the lens.

Misplacing a lens, a priori, does not cause any problems or side effects. The patient can easily know if the lens is not good, because it will not look good and comfortable as it should be when the lens is in place.

5. Care and maintenance
Maintenance. The lenses need cleaning and disinfection permanently.
Contact lenses should be removed daily at night to allow the cornea is oxygenated properly, otherwise it will be damaged.

There is, however, another type of lens, less widespread, because there is so many eyes that they can carry, which is the long-term use, allowing day and night wear contact lenses. In that case, no maintenance system, since they are a week replacement lenses.

The lenses need cleaning to remove debris from the tear, and disinfection, to kill all sorts of physiological waste (dead cells, lipids, protein) and microorganisms.

It should clean the lenses on the palm of the hand with special cleaning solutions that remove the remains of the tear film remaining after use. Then there’s another liquid for the conservation of the lens, which prevents contamination.

The patient, at night, you should leave the lens in the box with the solution. Today, two solutions are united, in many cases, a single fluid.

6. Bad habits and tips
Bad habits are fundamental overuse and lack of hygiene, which can cause problems in the medium-term. Overuse, understood not as the wearing lenses for many hours, since today’s materials are of high oxygen transmissibility, but the lack of change of the lens at the right time, often waiting more than necessary it is not bothersome.

Some practical advice to be taken into account:
- Maintenance solutions should not be open at least a month because there is a risk of contamination of the liquid, which can cause irritation or infection of the eye.
- Before handling lenses, should wash their hands, even under the nails, which preferably will be short.
- The need wetting lenses, especially soft. Are dehydrated due to natural body heat, so you need a special lubricant.
- You should not ever adapt, even cosmetic, without a prior study of the case and a complete eye examination and visual conducted by Optical-Optometrists.
- The management and care of the lenses and the case is important if you want to avoid not only premature deterioration, but a whole range of eye problems. Special attention should pay those using lenses sporadically.

7. Progressive lenses: field research
Potential. It’s huge because everyone is capable of using such lenses.
Progressive lenses are multifocal lenses through which the user can see clearly at all distances. Allow the combination of presbyopia with nearsightedness, farsightedness or astigmatism in a single lens, without jumps into view.

This is one area that is developing more and those who are investing larger sums of money because the lenses for presbyopia or farsightedness affect hundred percent of the population, so that potential users is the entire world.

The drawbacks of these lenses are caused by learning that the user should take to choose the image that is focused when he looks away, when you look closely or when looking at something in between. There are people that fit within hours and others not just to adapt and should desist.