What does the tear film consist of?

As mentioned above, the tear fluid must perform many different tasks. Therefore, the tear film must consist of several components to meet all the requirements of the eye. The tear film consists of: The tear fluid serves to increase the optical quality of the cornea.

All three components of the tears are necessary for this purpose. The optical improvement is mainly guaranteed by the aqueous phase. The fatty phase (lipid layer) reduces the evaporation of the tear fluid so that it can develop its full effect without evaporating beforehand.

The mucin phase improves the adhesion of the tear film on the cornea. All three together optimize the visual performance of the eye and also have a cleansing and moisturizing effect.

The outer lipid layer, which comes from the accessory glands
The aqueous layer from the lacrimal gland
The innermost layer, the mucin layer, also from the accessory glands

Examination of the lacrimal ducts

1. 1 Too little tear fluid If a patient suffers from “dry eyes“, too little tear fluid is produced. The problem lies with the tear glands.

To check the function of these glands, the ophthalmologist uses a relatively simple method: the Schirmer test. This test measures the production of tears. Here, after a local anaesthetic of the eye using eye drops, a narrow strip of an indicator paper is placed in the lower conjunctival sac.

The patient closes his eyes loosely. This paper changes color as soon as it comes into contact with the tears, so that the progress of the tear fluid can be read on the strip. There are now certain values that should not be undercut within a certain period of time.

So it can be determined whether enough tears are produced. 1. 2 Incorrect wetting by the tear film It is also possible that enough tear fluid is produced, but that it has an inadequate composition.

It is also possible that unevenness of the eye surface prevents adequate wetting of the eye. To check this, the so-called break-up time of the tear film is measured. For this purpose, the tears are stained and the slit lamp is used to observe how long it takes before the film breaks open.

The patient should not blink if possible. If the time is less than 10 seconds, this indicates that the mucin content of the tears is too low. A disturbed tear outflow can have many causes.

If too many tears are produced, the tear dots and the tear sac cannot transport and collect the entire amount and tear dripping occurs. If the tear dots are placed correctly, for example, if they protrude outwards, they cannot catch the tears properly. In order to be able to determine whether there is an outflow disorder, several methods can be used:

First, pressure is applied to the lacrimal sac to squeeze out the tears.
Once the way down into the nose is closed, the tears emerge through the tear ducts. So they follow the path in the wrong direction.
If you put eye drops with dye into the eyes, you can recognize the dye when you blow your nose. Then the tear ducts are free.
If the dye does not pass spontaneously through the lacrimal ducts, the doctor will help himself by rinsing them. Since rinsing is done with a saline solution, the patient should taste something salty when swallowing.
If the path is obstructed, the tear ducts must be probed with a blunt probe and if necessary the obstacle must be pierced. A stenosis (narrowing) often occurs in newborns.