Tonometry - Causes, symptoms and treatment. MF.
Tonometry is a method of determining intraocular pressure with a tonometer. Intraocular pressure is expressed in millimeters of mercury. There are two types of tonometry: contact and contactless.
Indications:
1. Age over 40 years( healthy persons tonometry should be conducted at least once a year).
2. Glaucoma( tonometry should be conducted at least once every 3 months).
3. Pain in the eyes, frequent headaches.
4. Presence of patients with glaucoma among close relatives.
5. Endocrine, cardiovascular and neurological diseases.
Contraindications to contact tonometry:
1. Corneal pathology.
2. Viral and bacterial eye diseases.
3. Allergy.
No contraindications to the use of contactless tonometry.
Conducting contact tonometry
At the heart of the method of contact tonometry is the principle of flattening the cornea. To do this, use the Maklakov tonometer, which is a hollow metal cylinder weighing 10 grams, inside which is a lead base. At the ends of this cylinder are two polished areas of white glass with a diameter of 1 cm
Tonometer Maklakova
Before the examination, the doctor( or nurse) wipes these areas with alcohol, and then they are applied a thin even layer of special paint containing a collargol( or bismarckboron), glycerin and distilled water. The paint is applied by touching the pad to a stamp pad impregnated with the dye. Surplus paint is removed with a dry cotton swab. For local anesthesia 3-5 minutes prior to the study, two drops of lidocaine are injected into the patient twice at intervals of 1 minute.
The patient lies face down on the couch. The doctor sits at his head.
Procedure for contact tonometry
The patient should lift his arm upward so that his eyes are facing directly to the index finger. The doctor carefully with one hand spreads the eyelids of the patient and drops the tonometer, which is in a special holder, with the other hand on the cornea. The tonometer should be lowered strictly vertically and strictly on the center of the cornea. The cornea is flattened under its weight. At the point of contact of the cornea with the colored area of the tonometer, the dye passes to the surface of the cornea, while the paint remains only on the periphery of the tonometer pad, and in the center there is a white dye, which has no dye. The essence of the method is that the higher the intraocular pressure, the denser the eye, therefore, the less the corneal flattening by the tonometer and the less contact of the tonometer with the surface of the cornea and, as a result, the diameter of the white circle is smaller. Conversely, the lower the intraocular pressure, the stronger the contact and the greater the diameter of the white circle. Then the doctor measures the pressure on this eye repeatedly, turning the tonometer over so that the used area is on top. To determine the intraocular pressure on the other eye, use another similar weight, 10 g.
It is assumed first to measure pressure on the right, and then on the left eye. After the procedure, disinfecting drops are instilled in the eyes( eg, r-r furacilin).
Then the obtained circles are alternately printed on pre-moistened with alcohol paper. The name of the patient, the date and time of the study must be indicated on this paper, it is necessary to note which prints are obtained from the right eye and which ones are from the left eye. The diameters of the obtained circles are measured by means of a special ruler, which immediately gives the result, expressed in millimeters of mercury.
For this method of normal pressure testing, 18-27 mm Hg is considered. Art.with diurnal fluctuations of 3-5 mm Hg. Art.(in the morning IOP is higher), so with a diagnostic purpose tonometry should be done in the morning and in the evening.
Conducting contactless tonometry
Non-contact tonometry is carried out using a special device that determines IOP by air strike. This method is simpler, fairly accurate and does not require preliminary anesthesia. But this requires the presence of a special apparatus.
The patient sits down near the apparatus, puts his head on a special stand and looks at a certain point. The device produces a flow of air with a certain amount of force. The level of IOP depends on the degree of flattening of the cornea under the influence of this flow. The result of the study is displayed on the screen of the device.
Procedure for contactless tonometry
Contact tonometry procedure is usually unpleasant for the patient, but absolutely painless;contactless tonometry can cause the patient some discomfort when the air stream hits the cornea, which can cause temporary tears;the procedure is also painless.
The duration of the contact tonometry procedure is on the average 10-15 minutes;The procedure for contactless tonometry takes several minutes.
Doctor ophthalmologist Odinochko Е.А.