Determination of intraocular pressure
Determination of intraocular pressure, depending on the influx and outflow of blood, the formation and outflow of intraocular fluid and its pressure on the walls of the eye, is a very important point in the study of the organ of vision. In the norm, the intraocular pressure ( eye tone) is between 18 and 25 mm Hg.and fluctuations between the parameters of the usually higher morning( 7:00 am) and lower evening( 19:00 pm) pressure should not exceed 3-5 mm Hg. Art. Increase in intraocular pressure is the main sign of severe eye disease - glaucoma, so knowing the state of intraocular pressure is necessary for diagnosing the disease, indications for medical and surgical treatment, and evaluating its effectiveness. It is equally important to recognize and lower the intraocular pressure, which accompanies a number of inflammatory and other processes in the eye. For an approximate determination of intraocular pressure, palpation is often used, based on a comparison of pressure( density) in the diseased and healthy eye. The patient closes his eyes and looks down, and the examiner puts the index fingers of both hands to the upper eyelid above the cartilage and gently presses on the eye alternately with each finger. The degree of pressure increase is denoted by one( +), two( ++) or three( +++) plus signs, the degree of decrease - by the minus signs, respectively. This study is of particular practical importance when it is impossible to use the instrumental method( for example, with corneal ulcers, penetrating wounds, after surgery).
For measuring intraocular pressure - tonometry - use special devices - tonometers. The most accurate of them is the Maklenov tonometer. It is a metal( or plastic) cylinder with a weight of 10 g, at the ends of which there are two porcelain platforms. Before the beginning of the study, they are lubricated with the paint prepared from collargol according to the following formulation: Collargoli, 2.0 g, Aq.destillatae, glycerini aa gtt XXX.The paint is stored in a jar with ground glass stopper. For tonometry, a bottle, a 0.25% solution of dicaine( or a 2% solution of lidocaine), a bottle with alcohol, wooden sticks with tightly wound cotton wool, moist, wrung, sterile cotton wool are placed on a separate tray. To measure the pressure, the patient is placed on the back on the couch, the eye is anesthetized by three-fold instillation of a 0.25% solution of dicaine( 2% lidocaine), and a pre-oiled tonometer is lowered onto the cornea, moving freely in a special handle. On the site of the tonometer there is a white circle - a flattening pad, which is imprinted with a tonometer attached to paper slightly moistened with alcohol. On a special scale in the set of the blood pressure monitor, measure the diameter of the light circle, which corresponds to a certain pressure expressed in millimeters of mercury: the smaller the light circle, the higher the pressure, and vice versa. For the accuracy of tonometry, two measurements are made for each eye, the difference between the data of which should not be more than 1 mm Hg. Art.
Elastotonometry is a method in which intraocular pressure is measured in series with four tonometers of different weights( 5, 7.5, 10 and 15 g).At the same time, the more the load of the tonometer is, the higher the pressure indicators. The obtained data of all tonometers, calculated on a special scale, where there are indications for all four tonometers, are drawn in the form of an ascending curve. Absolute numbers of indicators and their ratio gives a more accurate picture of intraocular pressure.
Even more accurate method - tonography - is produced with the help of modified tonometry( AP Nesterov), elastotonometry( SS Kaleda) on a special apparatus - a tonograph. At the same time, the quantitative characteristics of the production and outflow of the aqueous humor are determined.
Eye examination is performed after examination of the state of the functions of the central and peripheral vision, since they can change after the action of bright light during ophthalmoscopy and side illumination, palpation, eversion of eyelids and other manipulations.