Tear film examination. Study of tear production and drainage Norn test in ophthalmology

Schirmer test.

Two strips 5 mm wide and 40 mm long are cut out of laboratory filter paper of the “Filtrak” type. Their ends (5 mm) are bent at an angle of 40-45°. The patient is asked to look up and at the same time, with the finger of one hand, the lower eyelid of the right eye is pulled down, and with the other hand, the short curved end of the strip is carefully inserted beyond its ciliary edge in the lateral third of the palpebral fissure. In this case, the curved part of the strip with its end should reach the bottom of the lower fornix of the conjunctiva. Then the same procedure is carried out on the left eye. Immediately after inserting the test strips over the eyelids, start the stopwatch.

After 5 minutes, they are removed and the length of the moistened part (from the bend point) is measured using a millimeter ruler. Normally it is at least 15 mm.

When using other types of filter paper, the regulatory figures will differ. In particular, the results of studies conducted by V.V. Brzhesky and E.E. Somov (1998) showed that the normal wettability of test strips produced by Alkon is already 23 ± 3.1 mm.

Norn's test.

The patient is asked to look down and, pulling the lower eyelid with a finger, irrigate the limbus area for 12 hours with one drop of 0.1-0.2% sodium fluorescein solution. After this, the patient is seated at the slit lamp and, before turning it on, is asked to blink again and then open his eyes wide. Through the eyepieces of a working slit lamp (a cobalt filter must first be introduced into its system), the cornea is scanned in the horizontal direction. The time of formation of the first break in the colored tear film is noted. Most often it occurs in the lower outer quadrant of the cornea. In the course of research conducted by V.V. Brzhesky and E.E. Somov (1998), it was proven that healthy people at the age of 16-35 years, the tear film break time is 21±2.0 s, and at the age of 60-80 years - 11.6±1.9 s.

ADDITIONS

Burn degrees.

1.Hyperemia and chemosis of the conjunctiva, mild pinpoint opacification of the cornea. The surface layers of the epithelium are damaged.

2.Anemization, chemosis, conjunctival erosion, corneal opacity. The epithelium is damaged, with the exception of the germinative layer. The iris is not changed.

3. The conjunctiva is white, the cornea is intensely cloudy. Necrosis of all layers of the conjunctiva, epithelium, Bowman's membrane, and partially the native layer of the cornea. Irritation of the iris.

4. Disintegration of the conjunctiva and superficial layers of the sclera. Intense opacification and disintegration of the cornea. Necrosis of all layers of the cornea. Irritation of the iris.

EXAMPLES OF RESEARCH

OD sph-1.5 cyl -1.0 ax 90 (sph-1.5 - 1.0 x 90)

OS sph -2.0

This prescription means that the right eye requires spherical correction of myopia with a -1.5 D lens; there is astigmatism, which is corrected with a minus cylindrical lens of 1.0 D, while the axis of the cylinder, i.e. inactive meridian, located along an axis of 90 degrees. Spherical correction was prescribed for the left eye minus lens 2.0 D

OU sph +1.0 +1.5 add

In this case, bifocal lenses with a distance zone of +1.0 D and a near increase of +1.5 D were prescribed for both eyes.

OD Sph −2.0D Cyl −1.0D ax 179

OS Sph −2.8D Cyl −2.0D ax 173

Dp 68 (34.3/33.7)

For the right eye, correction of myopia (myopia) with an optical power of a lens of 2.0 D and correction of astigmatism using a cylindrical lens with a power of -1.0 D with a cylinder axis of 179 degrees is required.

The left eye requires correction of myopia (myopia) with an optical power of a lens of 2.8D and correction of astigmatism using a cylindrical lens with a power of -2.0D with a cylinder axis of 173 degrees.

The interpupillary distance is 68 mm; The distance from the bridge of the nose to the pupil of each eye is indicated in parentheses.

The Norn sample is diagnostic technique aimed at determining the stability of the tear film. The procedure is quite simple and does not require any preparation from the patient. During this procedure, a solution of fluorescein or analogs is instilled into the patient’s eye, which stains the tear film of the eye.

After this, the ophthalmologist scans the cornea using a blue filter element and a slit lamp. This approach allows any disruption of the tear film to be identified and appropriate action taken.

More about the Norn test

The Norn test has become widespread in ophthalmology, since it can confirm or exclude dry eye syndrome in a patient. This condition is fraught with a number of serious complications.

During the diagnostic process, the ophthalmologist can determine the stability of the tear film. She covers cornea eyes and performs a number of important functions. They are as follows:

• ensuring protection and removal of small foreign bodies from the cornea, preventing the growth and development of pathogenic microorganisms;
• providing natural lubrication for comfortable movement of the eyeball and blinking, preventing drying of the conjunctiva and cornea;
• supplying oxygen to the horny tissue and preventing the growth of blood vessels into it, maintaining its transparency;
• smoothing the surface of the cornea and ensuring correct refraction of rays for a clearer focus of vision.

Thinning tear film is the cause discomfort, sand in the eyes, redness and pain, which is fraught with much more serious consequences. By interpreting the results of the Norn test, the doctor has the opportunity to determine the time of tear film rupture, as well as a number of pathological changes in the cornea at the initial stage.

Indications for performing the Norna test:

• Suspicion of dry eye syndrome;
• Failures in the production of tear fluid due to taking pharmacological drugs;
• Pathologies of the cornea.

Contraindications to the Norna test:

• Individual intolerance to drugs used to color tear fluid;
• Pregnancy and breastfeeding period;
• Kidney diseases;
• Ulcerations of the cornea;
• Fistulas of the conjunctival sac;
• Childhood of the patient;
• Bronchial asthma.

How is the Norn test performed?

The procedure is simple and does not require the patient special training. All you need to do is visit the ophthalmologist’s office on time. He will be asked to take a sitting position and a 0.1-0.2% sodium fluorescein solution will be dropped into the eye or special strips with a coloring effect will be used.

Sodium fluorescein is a dye that has found widespread use in medicine for diagnostic studies. It is used with caution, excluding the presence of contraindications in the patient.

After applying the dye, the patient is asked to blink and avoid blinking during the examination using a slit lamp. An ophthalmologist examines the cornea and records the period of time during which the integrity of the tear film is disrupted. To do this, use a stopwatch, which turns off after the gap has increased.

Interpretation of Norn test results

In the process of interpreting research data, the ophthalmologist compares the results obtained and the Norn test indicators, which in ophthalmology are considered to be the norm. Since the test is carried out at least three times, using drops in each eye, the doctor operates on the average. When decoding, the patient’s age must be taken into account. The norm is:

• Breakup time 22.1 seconds in ages 16 to 35;
• Breakup time is 11.6 seconds for ages 60 to 80.

The Norn test is one of the methods for diagnosing dry eye syndrome. Dry eye syndrome is a lack of moisture on the surface of the conjunctiva and cornea.

Front side eyeball covered with a thin tear film, which protects the eye from direct exposure to the atmosphere and promotes washing out of the eye foreign bodies, provides the cornea with nutrients and oxygen, and has immunoprotective properties. The film breaks, and we blink to renew the tear fluid and restore the film. At the age of 16-35, the film breaks in approximately 21 seconds; with age, this interval decreases and by the age of 60-80 it is already 11.6 seconds. If the tear film breaks in less than 10 seconds, it is considered pathological, and in this case, dry eye syndrome is diagnosed.

How is the Norn test performed?

The Norn test is a test to determine how long it takes for the tear film to break. The patient is asked to look down, after which, pulling back the lower eyelid with a finger, the ophthalmologist instills a 0.1-0.2% solution of sodium fluorescein, which colors the tear fluid. Next, a scan is performed using a slit lamp and a blue filter. The patient is asked last time blink, after which he must look without blinking. This allows the doctor to time the first rupture of the film after blinking. The entire procedure (tinting the film, using a slit lamp and a light filter) is designed so that observing film breakage does not pose a problem.

Also, the Norn test makes it possible to detect already begun pathological changes cornea.

In most cases of dry eye syndrome, there are problems with the formation of tear fluid. There may also be changes in the composition and drainage of the solution that is produced by the lacrimal glands. To assess the condition of the eyes in this syndrome, not only clinical signs, but also a number diagnostic tests. For example, the Schirmer test is used to determine tear production; the fluorescein instillation test and the Norton test can be performed to study the tear film itself. To establish a diagnosis of dry eye syndrome, it is sufficient to identify a decrease in the amount of tears produced, as well as disruption (tears, instability) of the tear film.

To carry out the Norm test, a solution (0.1%) of a photosensitizer (sodium fluorescein) is used. You will also need a slit lamp with a blue filter to carry out the test. In this case, the illuminator is limited to a high slit (of medium width), and the angle with respect to the microscope should be 300. To increase the reliability of the examination, you can switch the operation of the slit lamp to the illuminator overheating mode. The overall sensitivity and specificity of the Norna test are quite high.

Methodology

During the Norna test, one drop of fluorescein solution is instilled into the patient's eye (on the limbus area). In this case, the subject’s gaze should be directed downward, and upper eyelid pulled back. Next, you need to blink once, and then open your eyes and try not to make blinking movements. The doctor starts a stopwatch and observes the stained surface of the tear cord through the slit lamp. Special attention is given to the cornea, the site where the tear film breaks, which looks like dry spot or a black hole.

At the moment when the tear in the tear cord increases in size or radial branches appear from it, the doctor must stop the stopwatch. The tear can be located in any area of ​​the surface of the eye, but its favorite location is the lower outer quadrant of the cornea near the tear meniscus. This is due to the fact that in this area the thickness of the tear film is thinnest. To get a reliable result, you need to test 2-3 times for each eye, and then average the obtained values.

Interpretation of results

In healthy people, tear film rupture occurs no earlier than 10 seconds after blinking. In the event that a violation of the integrity of the film is recorded in more than early dates, then there is a violation of the stability of the precorneal tear layer.

The Schrimer test is based on reflex stimulation of tear fluid production, as well as the absorbency of filter paper, which is placed in the conjunctival cavity.

The purpose of the study is to determine the amount of tears that are produced over a certain time.

The Schrimer test should not be performed in case of an ulcer or fistula of the cornea, extensive erosion of its surface, or in case of perforation of the eyeball.

Methodology

To carry out the test, you must use special filter paper strips. They can be produced in a set or you need to make them yourself (length 40 mm, width 5 mm). The end of the strip at a distance of 5 mm from the edge is bent at an angle of 40-450. Next, the patient is asked to look up, and this curved tip is placed under the lower eyelid of the eye (in the outer third). It is necessary that the edge of the strip touches the bottom of the lower fornix of the conjunctiva, then the bend will be located at the level of the edge of the eyelid. It is advisable to carry out the test on both sides simultaneously.

After administering the strips, the doctor should start the stopwatch and the patient closes his eyes. After exactly five minutes, the strips are removed and the length of the wet part is measured, starting from the point of inflection. If the wetting boundary cannot be established, the strips can be illuminated. When the wet boundary is located obliquely, the average result is taken into account.

Interpretation of results

In healthy patients, 15 mm test strips are wetted for 5 minutes. With a decrease in tear production, the length of the wetted test strip decreases; with hypersecretion of tear fluid, on the contrary, it lengthens significantly, reaching 35 mm within 2-3 minutes. The Schrimer test does not exclude a decrease in the main tear production, which may long time masked by its reflex enhancement.

Cost of diagnostic procedures

These studies are quite simple to perform and are inexpensive. The price of each of these procedures is eye clinics Moscow is about 500 rubles.