The technique of ophthalmotonometry by weights. Tonometer Maklakova: the device and application

The pressure inside the eye chambers is determined by the difference in the rate of inflow and outflow of fluid from them. The methods of tonometry used in clinical practice (pressure measurements) refer to the indirect methods and give a tonometric index of pressure.

Measurement of intraocular pressure is very important for the diagnosis of glaucoma and timely ophthalmic care for patients.

Tonometer Maklakov in ophthalmotonometry

In domestic ophthalmology, the most commonly used methods are contactless tonometry and measurement of intraocular pressure according to Maklakov. The latter was proposed in 1884, and entered into wide practice a little later.

Tonometry according to Maklakov consists in the short-term installation of a weight (tonometer) on the cornea of the eye and obtaining a print of the contact surface. The area of intraocular pressure is determined by its area.

In addition to the territory of the CIS, the method is widely used in China.

Tonometer of the eye Maklakova - completeness and device of the device

The set of the tonometer includes:

• Two cylindrical weights of 10 g in weight, extended at the ends with flat end faces;
• A holder for measuring, in which both weights can be fixed simultaneously;
• 3 measuring lines for estimating the diameter of a print or the ruler of Professor B. Polyak;
• case.

The cargoes are hollow inside, contain a lead weighting agent. Their end surfaces are made of frosted glass, which allows the ink solution to be uniformly retained.

The holder is needed so that during measurements with your fingers you do not create excessive pressure on the Maklakov tonometer.

Instructions for working with a tonometer

Before starting work, it is necessary to check the condition of the tonometer. Breaking the integrity of the end areas can damage the cornea of the patient's eyes. In addition, the cylinder should easily walk in the gap of the holder.

Treatment of Maklakov tonometers before use consists in rubbing the areas with alcohol, after which the device is dried for 15-30 seconds.

Sterilization by boiling in a 2% solution of baking soda for 30 minutes is carried out only in cases of extreme necessity:

• When a patient with signs of inflammation of the conjunctiva was examined;
• In case of threat in the department of viral keratoconjunctivitis.

As the Maklakov tonometer is not sealed, water can boil when boiled. To ensure that the results of ophthalmotonometry have not been distorted due to changes in the mass of the device, it is dried for an hour or more on a sterile gauze pad.

The paint applied to the Maklakov tonometer is a collargol (colloidal silver with albumin), which is ground in a mixture of glycerin and water. It is possible to use dyes bismarck-brown or methylene blue. To cover the plates with ink, use a stamp pad or transfer a drop of prepared dye with a glass rod, and then rub with a cotton swab. The latter way is safer in the epidemic plan.

The procedure for studying intraocular pressure with a Maklakov tonometer

Before tonometry, the patient's eyes are anesthetized. For this purpose, a solution of dicaine is added to the conjunctival sac twice at intervals of 2 minutes. The patient between the instillations covers his eyelids.

Further, the doctor or nurse performs the following actions:

1. Disinfection of Maklakov's tonometers with alcohol is carried out, they are dried.
2. A thin layer of paint is applied to the area of the tonometer.
3. The patient lies on the couch without a pillow, slightly lifting his chin, fixes his eyes on the index finger of his outstretched hand. The central part of the cornea should be in a horizontal position.
4. With the fingers of one hand, the researcher expands the eye gap so that the eyelids do not exert pressure on the eyeball.
5. With the other hand, using the holder, the Maklokov tonometer is lowered with a colored pad on the center of the cornea. Gruzik must completely fall to the eye with all his weight.
6. Next, the cargo is quickly lifted and an imprint is made on paper moistened with alcohol.
7. The study is repeated for the second eye.
8. The eyes of the patient are washed from the dye with saline and the Albucidum is instilled.

During the lowering of the tonometer on the cornea, the paint on the contact area is washed off by a tear. As a result, the impression is a ring.

Interpretation of the results of ophthalmotonometry according to Maklakov

The diameter of the light circle on the impression is proportional to the degree of flattening of the cornea during the examination. Accordingly, the higher the pressure, the less paint will be removed and, accordingly, the less light area of the print.

A transparent ruler measures the diameter of the light area. The researcher must place it downward to avoid distortion. The result is evaluated through a binocular loupe. The scale applied on the ruler allows you to immediately translate the result into millimeters of mercury.

When measured with a conventional ruler (up to 0.1 mm), the pressure reading is calculated as the ratio to the weight of the tonometer: the square of the radius of the print on the number of "Pi" and the specific gravity of mercury (13.6).

The norm of eye pressure according to Maklakov is the interval 18-26 mm Hg. Art.

Limitations and features of the method

It is not recommended to use tonometry according to Maklakov in the following cases:

• After a surgery on the eyeball;
• With allergic reaction to anesthetic;
• Inflammation of the eye and membranes.

Tonometer Maklakova has on the eyeball pressure, which exceeds this figure in other techniques, respectively, the result of the norm is shifted to a larger side. For comparison, the normal eye pressure according to Goldman is 9-21 mm Hg. Art. Therefore, the comparison of the results obtained by different methods will not be correct.