The examination of the intraocular pressure should be performed in people over 40 years of age, especially in farsighted people, when the eyeballs are small and predispose to the appearance of glaucoma. Intraocular pressure testing (tonometry) is also performed in cases of headache, pain in the area around the eye socket or in the eye.

The intraocular pressure test allows to determine the value of intraocular pressure, which must always be taken into account in the diagnosis of glaucoma and in the assessment of its advancement. With the current state of medical knowledge, it is known that the most effective method of fighting this disease is lowering the intraocular pressure, even if it is within the statistical norm.

Why is eye pressure measurement important?

In any type of glaucoma, it is important to establish a target pressure value, which is the pressure at which glaucoma does not progress.

Low voltage of the eyeball can be seen, among others, in in choroidal inflammation, in diabetes, after injuries, in leaky postoperative wounds, etc.

This value is different for each patient. Therefore, a correct result of the pressure in the eyes should not reassure you and slow you down from the need to perform further detailed diagnostic tests, let alone treatment. The level of intraocular pressure in a patient with glaucoma depends on the severity of changes in the optic nerve and in the field of vision. Additional factors that worsen the prognosis are also important, such as disturbances in the blood supply to the brain, abnormal blood pressure, disorders in the cardiovascular system, recurrent migraines now and in the past, freezing hands and feet, and myopia.

Methods of measuring intraocular pressure

There are several methods of measuring intraocular pressure, which differ in the measurement technique and its accuracy. Along with the development of modern research methods, these devices are more and more modernized so that the obtained measurement result is as close as possible to the real value.

  • Schiøtz Impression Tonometry

This is an old method, used since 1905, simple and cheap. it measures the pressure in the eyes by measuring the degree of corneal intussusception. It is still used in many clinics in Poland, thoughit is burdened with a measurement error and is very burdensome for the patient. In the era of rapid development of technology, it should be replaced by more modern methods.

  • Goldmann applanation tonometry

The measurement is based on the analysis of corneal flattening. The examination is performed in a slit lamp, it is unpleasant and requires anesthesia. The tip of the apparatus presses against the cornea, flattening it and thus measuring. A newer version of Goldmann's applanation is "ton-pen" electronic applanation tonometry. Compared to the older method, it has three main advantages, namely: a) it has a lower measurement error, b) the tip touching the eye has a disposable cover (cap) that is changed after each use and c) it exerts less pressure on the eye (flattening area of ​​the cornea) is smaller than in the case of older Goldmann planes.)

  • Pascal's Dynamic Contour Tonometry

Pascal dynamic contour tonometry equipped with a piezoelectric sensor. Unlike the applanation technique, which requires pressure on the cornea, the piezoelectric sensor in this method only touches the eye. The measurement result is independent of the corneal thickness, but it does not take into account its viscoelastic properties. The values ​​obtained by this method are often higher than the values ​​obtained by other methods. Pascal's tonometry also measures the amplitude of the ocular pulse.

  • Air puff tonometer

It is also a common method of measuring eye pressure. It measures the flattening of the cornea by a blast of air. The test is non-contact, but a sudden gust of air into the eye can be unpleasant. In patients with or suspected glaucoma, blood pressure measurement by this method is not sufficient. In these cases, it is recommended to measure the pressure using the applanation method. Modern air puffs work in the corneal response (CR) technology, which corrects measurement errors resulting from the failure to take into account the viscoelastic properties, i.e. the viscoelastic (stiffness) of the cornea. The viscoelastic properties influence the corneal hysteresis and thus the measurement result.

Intraocular pressure: interpretation of the result

Mean IOP value is 16 ± 3 mmHg. 21 mmHg is assumed to be the upper limit of normal, and values ​​over 21 mmHg are suspect glaucomatous. In some people, however, glaucomatous damage appears at a pressure of less than 21 mmHg (normal pressure glaucoma, JNC), and in others, symptoms are absent above 21 mmHg (ocular hypertension, NO). There are many factorsinfluence on altitude and should always be taken into account when assessing ocular pressure. The most important are tear film disorders, corneal surface disorders, central corneal thickness, disorders in the eye vascular system, incorrect eye positioning, excessive eye muscle tension, lack of proper patient cooperation and incorrect measurement by the examiner. When analyzing the intraocular pressure values, they must always be taken into account, in particular the central thickness of the cornea, which is measured by the pachymetry test.

More information on the IOP can be provided by plotting the so-called IOP curve. This curve requires several measurements per day (preferably over a two-day period). Not only do you get the pressure values ​​at different times of the day, you can also see how the pressure fluctuates. Differences greater than 4 mmHg are glaucomatous and are indicative of an increased risk of developing and worsening glaucoma.

About the authorBarbara Polaczek-Krupa, MD, PhD, specialist in eye diseases, Centrum Opulystowa Targowa 2, Warsaw

Dr. Barbara Polaczek-Krupa, MD, initiator and founder of the Targowa 2. Ophthalmology Center. She specializes in modern diagnostics and treatment of glaucoma - this was also the subject of her PhD thesis defended with honors in 2010.

Dr. med. Polaczek-Krupa has been gaining experience for 22 years, since she started working at the Ophthalmology Clinic of CMKP in Warsaw, with which she was associated in 1994-2014. During this period, she obtained two degrees of specialization in ophthalmology and the title of doctor of medical sciences.

In the years 2002-2016 she worked at the Institute of Glaucoma and Eye Diseases in Warsaw, where she gained knowledge and medical experience by consulting patients from all over Poland and abroad.

For years, as part of cooperation with the Medical Center of Postgraduate Education, he has been a lecturer at courses and trainings for doctors specializing in ophthalmology and primary he alth care.

He is the author or co-author of numerous publications in scientific journals. Member of the Polish Ophthalmology Society (PTO) and the European Glaucoma Society (EGS).

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Research