Ophthalmology

Dry eyes

Definition of dry eyes

With dry eyes it is mostly a disorder of the tear film. As a result, there is a faulty and insufficient wetting of the conjunctiva and cornea of the eye.

Dry eyes result from a disturbance in the wetting of the surface of the eye. A faulty composition of the tear fluid is blamed as the cause. Other underlying diseases or medication can also be the cause. Those affected mainly suffer from a feeling of dryness and itching. Tear substitutes are mainly used for therapy.

Occurrence in the population

The dry eye occurs more and more often in old age. Women are usually more affected than men.

Causes of dry eyes

The production of tear fluid follows a time-dependent rhythm and takes z. E.g. in the evening. Apart from these fluctuations, there is also decreased tear production with disease value.

A faulty tear film is mainly responsible for the development of dry eyes. Since the tear film consists of three different phases from the outside in:

Layer of fat
aqueous layer
Mucin layer

The cause of dry eyes can be sought in all of the three layers.

Depending on which type of gland is affected, a different phase of the tear film suffers:

Most of the time, the volume of the Lacrimal gland something back, from which the aqueous phase suffers. It is then produced in insufficient quantities.
Work the Meibomian glands of the lid is no longer complete, too little of the fat phase is produced. If the Goblet cells the conjunctiva, on the other hand, reduces the proportion of the mucin phase.

In addition to the sole dysfunction of the various types of glands, dry eyes are also a symptom of various underlying diseases:

Sjogren's Syndrome:
Sjogren's syndrome is a chronic inflammation of several joints with a reduction in the secretion of various salivary glands.
Dry nose and mouth are also typical here. Here, the moisturizing of the eyes can be so disturbed that a corneal ulcer (ulcer = ulcer) develops. A breakthrough through the cornea can also occur. In this case, a corneal transplant only makes sense if the future of moistening of the eye is ensured (e.g. with tear substitutes).
You can find out more about this topic at: Sjogren's Syndrome.
Facial paralysis:
Facial paralysis is paralysis of the nerve that supplies the facial muscles in the face.
If this nerve (facial nerve) has failed, the facial muscles can no longer be moved. These muscles also include the muscle that enables the eyelid to close. If this can no longer be carried out, the cornea will be damaged in wetting due to the lack of eyelid closure. As a result, the tear fluid is no longer distributed over the surface of the eye.
1. Read more on this topic at: Facial palsy
Trigeminal Palsy:
If the trigeminal nerve is paralyzed, the secretion of the lacrimal gland in the outer upper corner of the eye can no longer be adequately controlled. The production of tear fluid then decreases.

Furthermore, the dry eye also occurs in connection with certain medications. Some are briefly mentioned here: beta blockers (against high blood pressure), local cortisone preparations (i.e. eye drops or ointments that contain cortisone) and the “pill”.

A variety of diseases can be the cause of dry eyes. In addition to systemic diseases such as diabetes mellitus ("sugar"), neurological failures (paralysis of nerves) also play a role.

What are the symptoms of dry eyes?

Symptoms that people with dry eyes experience include:

Feeling of dryness
Foreign body sensation
itching
Burn

The intolerance of cosmetics or contact lenses can also be an indication of dry eyes. The eye becomes generally more sensitive, so that even a breeze can cause pain.
These subjective complaints are perceived differently and unpleasantly by each patient.

Read more on the topic:

Dry eye symptoms
Eye pain
Blurred vision - what's behind it?

The diagnosis

The diagnosis The doctor determines dry eyes based on the symptoms described. The Schirmer test and the Tear-open time.

First and foremost, the incorrect composition of the tear film comes into question, so this should be clarified. The so-called Schirmer test, in which a strip Litmus paper is hooked into the lower conjunctival sac of the locally anesthetized eye. If the tear film lacks the appropriate amount of aqueous component, the strip would stain less than 5 mm. That would be an indication that the lacrimal gland is not working normally. If the Schirmer test is normal, but the break-up time is shortened, then there is probably a reduction in the function of the conjunctival goblet cells.

The various other causes should also be clarified, but are associated with a lower percentage. See also Diagnosis

Dry eye therapy

The simplest therapy for dry eyes is to prescribe a tear substitute in the form of eye drops or eye gels (see also: Euphrasia eye drops), which should then be dripped into the eyes several times a day.
The tear fluid is replaced and the wetting of the cornea is guaranteed.

A wide variety of preparations are available that can be selected individually. They differ in the basic materials used, but also in their viscosity (drops or gels).
If the patients suffer from allergies, products without preservatives should be used.

These articles might also interest you:

Eye drops for dry eyes
The vitamin A eye ointment

What are the consequences of dry eyes?

On the one hand, dry eyes lead to typical symptoms such as eye pain, redness, sensation of foreign bodies and burning sensation, which can significantly disrupt the patient's quality of life.

If the disease is ignored further, however, considerable consequential damage can occur.

In a first phase dry eyes can lead to further complications Inflammation and damage to the cornea and the eyelid come. Eye infections, such as conjunctivitis are much more likely than healthy eyes because the eyes are constantly irritated.

If the eye continues to remain chronically dry, it can become a Drying out of the corneal surface come. This results in changes in the uppermost corneal cell layer. These changes lead to clouding and even scarring of the cornea. Cloudiness and scarring can be painful and significantly worsen vision.

In addition, small vessels can sprout into the cornea (Angiogenesis). This will also restore the Vision negatively affected. In this phase, irreversible processes can already have occurred. In the worst case scenario, there is a risk of complete blindness.

What is the prognosis?

Dry eyes have in the strict sense not a high disease value. So there is no organ damage, life expectancy is not influenced, etc.
After a long time, however, the corneal surface can become cloudy, especially if the eye can no longer be closed (e.g. due to paralysis of the facial nerve). Unfortunately, this cannot be counteracted as easily as the inadequate tear production, which simply occurs through eye drop is replaced.

prophylaxis

To prophylaxis of dry eyes, care should be taken to ensure sufficient humidity in closed rooms.
Especially in the winter The dry heating air must be prevented by placing water-filled vessels. But also with air-conditioned rooms in summer there is a risk that the air does not contain enough moisture.

Dry eyes and contact lenses

Contact lenses can also cause dry eyes and are a common problem for those who wear contact lenses.

causes:

Usually the dry eyes come from too strong one Airtightness contact lenses, which means that the oxygen supply that supplies the cornea is too low.

In addition, the tear fluid under the lenses slowly evaporates during the course of the day, especially due to heat or wind. The lenses can also impair rewetting by blinking. Another factor can be that the flow of tear fluid through the contact lenses is impaired. Carriers are particularly at risk softer contact lenses, because soft contact lenses are elastic and adapt completely to the surface of the cornea, so little oxygen and tear fluid get under the lens and thus to the cornea. For this reason, soft contact lenses are more suitable for people who only wear their contact lenses a few times a week.

At hard contact lenses there is less risk of dry eyes, as hard contact lenses are usually smaller and do not cover a large part of the cornea. In addition, they do not adapt well to the shape of the cornea, so that overall more oxygen and tear fluid can reach the cornea.

What should you watch out for when wearing contact lenses in order to avoid permanently dry eyes?

On the one hand, you should prefer hard contact lenses if you wear them daily. In addition, it is also recommended that contact lenses, which according to the manufacturer are also suitable for wearing at night, be removed from time to time at night to protect the eye from further dehydration.

It is also important that the lenses are removed as soon as possible if discomfort occurs. Complaints can be an uncomfortable feeling through the lenses with dry eyes, or even a blurred vision due to the dryness of the eyes. It is important to pay attention to these complaints, otherwise it is easy to Inflammation of the eye, as the dryness chronically irritates the eye.

In addition, with soft contact lenses you have to have one every six months Examination at the ophthalmologist should be carried out, with hard contact lenses, on the other hand, once a year is sufficient if there are no complaints. A doctor's visit should also take place if there are no subjective complaints, because it can with no perceived discomfort Changes in the eye can already be seen by the specialist.

If symptoms such as dry eyes from contact lenses are already present, one is on adequate care of the lenses and a adjusted wearing time to pay attention. You should always observe the recommended maximum wearing time of the lenses. There are also special ones Moisture solutions or Tear substituteswhich can alleviate the discomfort. When choosing contact lenses, it is also important to choose a product with high permeability or a product that can balance the fluid balance through the tear film of the eyes; there are special lenses for this Silicone hydrogel or lentils with a high content of hyaluronic acid. The hyaluron stores fluid instead of releasing it to the outside. In contrast, a product with a high water content in the contact lenses without storing the liquid usually ensures that more water evaporates and the eyes are deprived of moisture. Therefore, one should seek advice from an ophthalmologist when choosing lenses.

Dry eyes at night

The fact that many people complain of dry eyes, especially at night, has several causes. On the one hand lacks blinking while sleeping. As a result, the tear film can no longer be distributed so evenly over the cornea Dirt, foreign bodies, cell debris, inflammation mediators and pathogens not worn away. The interrupted flow of tear fluid can then lead to the adhesion of pathogens. In addition, the production of tear fluid by the lacrimal gland decreases during sleep at night. This not only promotes dehydration of the eyes, but also the adhesion of pathogens, since the accessory lacrimal glands also promote the production of class A immunoglobulins (IgA) to adjust. IgA normally ensures a quick defense against pathogens such as bacteria in the mucous membranes.

All of this means that fluid is absorbed through the conjunctiva at night instead of through tear gland production and blinking as during the day. But even with dry eyes during the day, the eye can absorb fluid and oxygen via the vessels of the conjunctiva via a kind of 'emergency supply'. Normally, oxygen is also absorbed through the air and the connection to the tear film, which is more difficult with dry eyes. During the night, this process intensifies even further.

All of this has the consequence that especially people who already have dry eyes anyway red, extremely dry eyes wake up. It can also go so far that even the Eyelids swollen because here, too, vessels were used to supply the conjunctiva. Therefore, the use of tear substitutes can be helpful when waking up or at bedtime.