Determination of tearoproducts and stability of the tear film (Sherimer and Norna sample). What is the problem of NORN? Investigation of the breaking time of the tear film using fluorescein

24.05.2020

Norna test is carried out to determine such an indicator as the breaking time of the tear film. This study is necessary to confirm or eliminate the dry eye syndrome when there is insufficient production of tears and the cornea does not receive the necessary moisture. Such a pathological condition is dangerous complications, in particular, the loss of visual acuteness. The diagnostic procedure is carried out in the conditions of polyclinic on the latest equipment.

Study of the tear film: testimony and method

Excessive seating for PC and constantly working air conditioning increases the risk of dry eye syndrome. With such pathology, damage to the surface elements of the visual system often occurs. The norm is required when a person is disturbed by normal tear, that is, the amount of basal tears decreases. It is carried out quickly, not harming health and without pain sensations. In the process of conducting research, a person should look only down all the time. The sample is carried out in stages:

The lower eyelid should be delayed.
With the help of a small amount of the fluorescein sodium salt solution, a lacrimal surface is painted. In addition, special strips are applied to change the color, which are placed under the lower eyelid. Keep them in such a state for 2-3 seconds. This is enough for the mucosa surface to change its shade to yellow.
For subsequent actions, with a sample of Norna, the doctor applies a slit lamp.
The patient will need to smorn, and then open and keep the eyes as wide as possible.
Using the oculyars of the device is carried out checking the horny shell. The main task is to fix the period for which the integrity of the interrogue film is broken.
The stopwatch used is turned off when the gap will increase or the rays will go from the scene.

Results: Interpretation and norms

After a three-time study on each organ, the doctor will calculate the average indicator, on the basis of which a certain conclusion will be made.

Sample Norna must have the results adopted as the norm. Often, changes occur at the bottom, where the film thickness is minimal. In order to get an accurate result, a specialist conducts such a test several times (at least 3 times per eye). From the figures obtained, the average is determined. The norm for each group of patients is different. It depends on age categoryThe main indicators are presented in the table:

Basically, the specialist makes conclusion about changing the stability of the intermediate tear film, if the breakthrough arose less than 10 seconds after the blink.

Norna test is one of the methods of diagnosing dry eye syndrome. The dry eye syndrome is a shortage of moisturizing the surface of the conjunctiva and cornea.

The front side of the eyeball is covered with a thin tears film that protects the eye from the immediate effects of the atmosphere, contributes to washing out of the eyes of foreign bodies, provides a cornea with nutrients and oxygen, has immunically protective properties. The film is broken, and we are blinking to update the tear liquid and restore the film. At the age of 16-35, the film rupture occurs in about 21 seconds, with age, this interval decreases and by 60-80 for 11.6 seconds. If the gap of a tear film occurs in less than 10 seconds, it is considered pathology, and in this case is diagnosed with dry eye syndrome.

How to test NORN

Norna's sample is a test that allows you to determine what time a tear film is breaking. The patient is asked to look down, after which, pulling the lower eyelid to the finger, the ophthalmologist also bursts 0.1-0.2% sodium fluorescene solution, which stains the tear fluid. Next, scanning is performed using a slit lamp and a blue filter. The patient is asked to blink the last time, after which he should look, no longer blinking. This allows the doctor to retrieve the time of the first break of the film after the blink. The whole procedure (film tinting, the use of a slit lamp and a light filter) is built so that the observation of the film breaks does not imagine.

Also, the test of Norna makes it possible to detect the already started pathological changes in the cornea.

Norna's sample is a diagnostic technique aimed at determining the stability of a peeling film. The procedure is quite simple and does not require a patient training. When it is carried out in the patient's eye, the fluorescein solution or analogues are stained, which paint the tears of the eye.

After that, the ophthalmologist scans the horny shell of the eye using the blue filtering element and the slit lamp. This approach allows you to determine any violation of the tears and take appropriate measures.

Indications for testing Norna:

Suspicion of dry eye syndrome;
Tellular fluid production failures due to the reception of pharmacological preparations;
Pathologies of the horny shell eye.

Contraindications for conducting sample Norna:

Individual intolerance to the preparations used for staining of the tear fluid;
Pregnancy and breastfeeding period;
Kidney disease;
Ulceration of the horny shell of the eye;
Conjunctival fistula;
Children's age of the patient;
Bronchial asthma.

How to spend a sample NORN?

The procedure is simple and does not require a patient special training. All that is needed: to visit an ophthalmologist in time. It will be asked to take the situation sitting and get into the eye 0.1-0.2% solution of sodium fluoresin or use special strips with a staining effect.

Fluorescein sodium is a dye that has found widespread use in medicine during diagnostic studies. It is used with caution, eliminating the presence of contraindications in the patient.

After applying the staining substance, the patient is offered to smorn and exclude the blink during the inspection process using a slit lamp. The ophthalmologist conducts a study of the cornea and fixes the segment of the time through which the integrity of the peeling film is disturbed. For this, a stopwatch is used, which turns off after the gap has increased.

Interpretation of the results of the sample of Norna

In the process of interpretation of these studies, an ophthalmologist compares the results obtained and the test indicators of Norna, which in ophthalmology is considered for the norm. As the test spend at least three times, instigating each eye, the doctor operates with an average. When deciphering, the patient's age is necessarily taken into account. The norm is considered:

Break time 22.1 seconds aged 16 to 35 years;
The break time is 11.6 seconds aged 60 to 80 years.

Since soft contact lenses We directly interact with a lacrimal film and for their comfortable wearing requires a sufficient amount of tears, it is necessary to carry out a quantitative and qualitative assessment of the tear film, which will help to prevent possible problems.

Typically, the thickness of the film is 7 microns

The average volume of tear fluid eye - 6 μl

Time of complete evaporation of the lacrimal film 10-20 s

Migration time is normal - every 5-10 s

For the study of the lacrimal film, there is a special device -Taskop, with which you can detect the most initial changes in its structure. However, in everyday practice there is no need for this, so we will focus on the simplest methods that allow you to distinguish the norm from pathology.

Quantitative evaluation of tear fluidyou can spend using the following methods:

Sample Shirmer

A qualitative assessment is carried out by methods:

Study of tear meniscus

Study of the breaking time of the tear film

4.1. Structure of tear film

Layer of water and dissolved in it nutrients The cornea is called a tear film. This film is constantly produced and removed from the eye surface. The lacrimal film consists of:

Lipid layer

Water layer

Mucin layer

Lipid layer

Provides gliding conjunctiva upper century On the surface of the eye

Protects the cornea from drying

Water layer

Provides a cornea with oxygen and nutrients

Immune defense (lysozyme)

Wash out of the eye foreign bodies

Muzzin layer

Binds a lacrimal film with a cornea

Makes the surface of the cornea smooth and smooth, thereby providing high quality of view

4.2. Study of tear meniscus

The tear meniscus is the thickening of the tear film at the rear edge of the lower eyelid. To assess its condition, the biomicroscopy technique is used, if possible, with a "grid", with a large increase (X25) and avoiding bright lighting, so as not to interfere with the tear reflex.

Methodology:

Compare both eyes

Examine to any instillations and manipulations

The study of the tear meniscus helps to assess the volume of tears:

Normally: Menisk Width 0.3 -0.4 mm

Insufficient tears - Menisk 1.0 mm

and the quality of tears:

Normally: Meniscus is smooth border, convex form

In pathology: Improper form and faster edge

4.3. Investigation of the breaking time of the tear film by non-invasive methods

The study is carried out without using any dyes, which makes it possible to eliminate the irritating and causing tearing the action of medicines.

The examination is carried out on a special device - a copyoscope, but if it is not, you can use a conventional keratometer and, in this case, the indicator serves as a time at which the picture of the labels disroached on the cornea begins to break.

The method allows you to estimate the stability of the tear film, namely the function of the mucin layer.

Results:

Normal\u003e 30 s

Border states: from 10 to 30 s

Pathology< 10 с

4.4. Investigation of the breaking time of the tear film using fluorescein

This method allows you to estimate the stability of the tear film using fluorescein.

After instillation of fluorescein, using a blue cobalt biomicroscope filter, we define the time when the roar of the cornea is destroyed by a lacrimal film, which is visually defined as the appearance of dark spots on a flat background.

Results:

Norm from 10 to 45 s

Methods of research of tearoproduks

Comprehensive examination of the tear-producing apparatus Includes an assessment of the stability of the discronized tears and the measurement of the secretion of the tear fluid (total, as well as if necessary, the main and reflex).

Determine the time of the stability of the distributed tears.

Determine the total amount of secreted teasel fluid.

Determine the amount of the main (carried out by additional teasel glands) the secretion of the tears fluid.

Indications

Syndrome "dry eyes" and suspected of it with normal values \u200b\u200bof the Siberiana sample.

Contraindications

Similar to those in the formulation of the Sibermer sample.

Preparation

The test strip is prepared as when performing a sample of Shirr. In the conjunctival cavity bury eye drops with anesthetic.

Methodik

After instillation of the solution, anesthetic from the lower conjunctival arch gently absorb the tear and the remnants of the preparation with a cotton swab. Then, for the lower eyelid of the patient for 5 minutes (as when conducting a swirder sample), the filter paper strip is placed and the resulting result is evaluated.

Interpretation

Normably in 5 minutes is wetting at least 10 mm test strips. Smaller sample values \u200b\u200bindicate a decrease in the main tearoproduction.

Since the spelling sample allows us to estimate the volume of general, and according to Jones - basic tear products, the difference of their results characterizes the number of reflexively separated tears (normally not less than 5 mm). However, its "reserve" is significantly higher than this value, since the stimulus used in the examined tests (filter paper) is far from the strongest.

Operating characteristics

The sensitivity of both samples (wiring and Jones) is satisfactory. False negative test results are associated with excessive irritation of the cornea with improper placement of the strip.

The specificity of both samples is very high (provided that the method of their production is observed).

Factors affecting the result

The erroneous results of the considered samples may be caused by an improper arrangement of the test strip, namely the contact of it with the cornea, excessive irritation of eyelashes and skin of the eyelid. As a result, there is an excessive stimulation of reflex tears and a false-negative result of samples. For the same reason, the eyelid opening during the study is unacceptable. However, the largest number of erroneous conclusions when setting under the samples are related to the inadequate quality of filter paper for the preparation of the test strip, therefore it is preferable to use their standard branded sets (see Fig. 8-2).

Complications

Not noted (taking into account contraindications to the formulation of the sample).

Alternative methods

Methods for measuring tear products using a test thread It is based on the definition of the time required for wetting the segment of hydrophilic (polyvinol, cotton, etc.) of the thread placed in one end for the lower eyelids of the surveyed (as when performing a sample by the store). The result of the sample depends on the material and thickness of the test thread used. The method allows you to evaluate both the total tearoproduction and its main components.

Laktorrreen testit is aimed at measuring the concentration of lactoferrin in a tear (it is produced by peeling glands). The decrease in the concentration in the tear of the studied protein to 0.92 mg / ml is evidenced by the reduction of the concentration in the tear of the protein under study and below. A simplified method of determining the lactoferrin in a tear using the Lactoplate portable analyzer has been developed. The method is designed to estimate the number of main tear products.

Sodium fluorescein breedingit is based on fluorofotometric observation of a decrease in the concentration of the dye in the conjunctival cavity as it is "dilution" of a constantly secreted tear. The sample allows you to estimate the number of basic tear products.

Methodology for estimating the height of a tear meniscus. With the help of a slit lamp (with a thin slit), the ratio of the vertical and horizontal components of the lower tears meniscus in the adjustment zone of the free edge of the lower eyelid to the cornea is evaluated. Normally, the height of the tears of meniscus is 2 times the basis. If the ratio under consideration changes in favor of the vertical component, the deployment is diagnosed if the horizontal decrease in tear products. The sample is used to measure the volume of the fluid at the time of study in the conjunctive cavity, which indirectly allows you to evaluate the main tearoproduction.

Evaluation of active passability of tear paths