What is intraocular pressure?

Intraocular pressure is the pressure created by the fluid inside the eye. It can fluctuate slightly and depends on various factors – a person's well-being, health and age, and time of day.

Why do I need to monitor my intraocular pressure? A high or low reading may indicate an eye disease. For example, glaucoma, which without treatment can lead to blindness. Often problems with intraocular pressure are detected in a situation when conservative treatment is almost impossible. This is why annual preventive examinations by a doctor are so important.

Norms of intraocular pressure

In normal cases, the intraocular pressure (IOP or ophthalmotonus) is between 10 and 20 mm Hg (millimeters of mercury). Slight fluctuations are possible during the day: the difference of the intraocular pressure values during the day may be within 1-3 mm Hg.

After the age of 40 the intraocular pressure becomes more unstable, and the indexes increase. This is why doctors recommend having a complete ophthalmologic examination every year at least once a year.

Symptoms of intraocular pressure abnormalities

High and low intraocular pressure is mistaken by many for fatigue. This is why the disease remains unnoticed for a long time, leading to irreversible changes in the structures of the eye.

The following symptoms should alert you:

  • Pain in the area of the eyebrows;
  • Deterioration of vision;
  • Unreasonable lacrimation;
  • "Burst" blood vessels in the eye;
  • Dry, stinging, burning or foreign body sensations in the eye;
  • The appearance of flies, dots in the eyes or a halo effect around a light source;
  • Rapid general fatigue.

If symptoms are systemic, be sure to see your doctor.

Causes of abnormal intraocular pressure levels

Elevated or decreased intraocular pressure is usually the result of some kind of disease. The most common diagnoses of impaired ophthalmotonus are:

  • Glaucoma;
  • Infectious and inflammatory eye diseases (conjunctivitis, blepharitis, keratitis, etc.);
  • Vascular diseases;
  • Chronically high blood pressure;
  • Abnormalities in the shape of the eyeball;
  • Refraction disorders – optical power of the eyes (usually farsightedness – hypermetropia, especially age-related).

IOP abnormalities may be caused by excessive tea or coffee consumption, which affects cerebral blood vessels.

What are the dangers of ophthalmotonus disorders?

The main danger of increased or decreased intraocular pressure is the total irreversible loss of vision.

When the intraocular pressure is elevated, the first thing that happens is changes in the fine nerve structures, and the pressure is exerted on the optic nerve disk. At first, the visual field narrows slightly, but the patient may not pay attention to the change. Meanwhile, the visual function continues to deteriorate.

If the intraocular pressure is reduced, the vitreous body, the gel-like framework of the eyeball which gives it its shape and elasticity, deteriorates. The eye gradually atrophies and shrinks. The patient does not notice the deterioration of vision longer than in case of increased ophthalmotonus. In this respect, a decrease in intraocular pressure is the most dangerous.

Checkups help detect changes in time, thus stopping the pathological process and keeping the disease under control.



Usually the patient does not complain about intraocular pressure because he is not aware of the problem. The doctor is helped by the above symptoms, as well as by external examination and palpation of the eyes through the closed eyelids to assume an ophthalmotonus disorder.

Intraocular pressure is measured instrumentally using a special tonometer. It can be either contact or non-contact.

Contact methods can be painful, so local anesthesia may be needed. Staining of the cornea is also necessary, which also makes the patient uncomfortable.

Non-contact methods are modern ways of measuring intraocular pressure. They are painless and do not require additional corneal staining.

The most advanced devices for measuring are immersion tonometers, such as Icare. It determines the pressure by bouncing – a small sterile tip quickly touches the cornea, and the patient does not feel it. The device gives accurate readings.

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