Ocular hypertension: what is ocular pressure and why it should be controlled

By Cristiano Antonino On Mar 11, 2023

Let’s talk about ocular hypertension: taking care of one’s eyes is just as important as taking care of other parts of the body, but we often underestimate the warning signs until the disorder becomes unbearable

One of the values to which one should pay attention and for which a regular eye examination is necessary is that of eye pressure, which, if altered, could impair vision.

What is eye pressure

The eyes also have their own pressure, which arises from the balance between the secretion of aqueous humour from the ciliary blow and its outflow from the eye.

In practice, the eyes produce and drain fluid, activities that keep the intraocular pressure in an acceptable range.

If this does not happen and especially in the case of ocular hypertension, one could be facing very serious pathologies, such as glaucoma.

What are normal intraocular pressure values

Eye pressure should remain within a range of 10-12 mm of mercury (mmHg) to a maximum of about 21-22 mmHg.

A pressure within these values ensures correct vision and good eye function.

Caution, however: range values should always be interpreted in relation to corneal thickness, and are therefore valid for a cornea measuring 530 microns.

Should one be faced with a higher or, on the contrary, a thinner thickness, one must re-evaluate the value of the intraocular pressure by adjusting it to the cornea.

This is why it is always useful to combine eye pressure measurement with pachymetry, i.e., the test that evaluates the thickness of the cornea.

Measuring eye pressure is, therefore, an assessment that takes several aspects into account, just as it is for blood pressure.

How to measure ocular pressure

Measuring eye pressure regularly is important to check the health of your eyes and is essential in cases where sudden vision problems occur.

The measurement is carried out by the eye doctor using a test called tonometry, which makes use of different types of tonometers

blow tonometer, which involves no contact with the cornea and produces a jet of air
applanation tonometer, the most widespread and accurate, which consists of a cone placed in contact with the eye that measures the resistance of the ocular surface
rebound tonometer, which uses a small probe that makes contact with the cornea

If the tonometry reveals intraocular pressure abnormalities, the doctor may prescribe other tests to confirm the diagnosis.

In particular, among the most frequent tests used to confirm or not the diagnosis are:

gonioscopy, which analyses the space between the iris and the cornea, where the aqueous humour outflow channels are located, detecting whether they are obstructed, open, reduced or totally closed
ophthalmoscopy, which allows us to examine the ocular fundus and thus the optic nerve by projecting a beam of light through the pupil onto the retina.

High ocular pressure

Hypertension of the eye, i.e. values above, on average, 22 mmHg, is due to an alteration in the amount of aqueous humour, the transparent liquid inside the anterior and posterior chambers of the eye.

When an excessive amount of fluid is present, intraocular pressure rises.

High eye pressure can lead to optic nerve damage and even blindness, particularly when associated with glaucomatous disease, as is often the case.

Causes of high eye pressure

The causes of high blood pressure can be diverse, some directly related to the functioning of the eyes, others associated with external factors.

Causes related to the eyes obviously include excessive production of aqueous humour and insufficient drainage of it, but also eye diseases such as pseudo-exfoliation syndrome, while external factors include:

severe stress and anxiety
consumption of caffeine, alcohol and drugs
smoking
ocular trauma
difficult pregnancies
pressure surges
diabetes, high blood pressure and heart disease
excessive consumption of red meat, sugar, salt
certain medications

External factors can cause temporarily high intraocular pressure. In these cases, hypertension can be resolved by adopting different habits and a healthier lifestyle.

In other cases, however, it must be kept under control to avoid the onset of glaucomatous diseases.

Symptoms of high ocular pressure

Noticing high eye pressure is impossible, because there are no obvious signs of altered values at least until serious consequences such as damage to the optic nerve and thus glaucoma arise.

Only the ophthalmologist can assess whether or not the eye pressure is within the range through a thorough eye examination in which he or she measures the pressure using a tonometer.

Glaucoma and ocular hypertension

Glaucoma is an eye disease that affects the optic nerve and impairs vision, even completely.

It is a progressive disease, is the second leading cause of blindness in Italy and is, in most cases, due to increased intraocular pressure (in rare cases it is congenital, from birth).

How high ocular pressure is treated

There is no real cure for intraocular hypertension, but there are eye drops to prevent the onset of glaucoma or, if it already exists, to keep it at bay.

These are hypotensive eye drops that are based on four different molecules and aim to keep eye pressure within the range considered ‘normal’.

In some cases, surgery to reduce eye pressure may be considered, such as trabeculectomy, which involves the removal of a portion of external eye tissue in order to create a small additional duct through which the aqueous humour can drain.

Low eye pressure

There is not only high ocular pressure: in some cases, intraocular hypotonia can develop, i.e. when pressure values are below the minimum considered normal, i.e. 10-12 mmHg (always taking into account the patient’s specifications and horny thickness).

Low ocular pressure is less frequent but must still be kept under control.

It can be the consequence of trauma or complications following surgery, and is easily detected because below 10 mmHg vision begins to decrease significantly, although this symptom can vary from patient to patient and some are completely asymptomatic even with lower values.

Eye pressure and children

Unfortunately, there are cases of congenital glaucoma, in which the condition is therefore present from birth due to the inability of the eye to produce and drain the aqueous humour properly, resulting in a constant increase in eye pressure.

It is therefore important to have children’s eyesight checked regularly by an eye examination in order to detect the pathology at an early stage.

When to have eye pressure measured

Having intraocular pressure measured is important to keep high values at bay and to curb the onset of glaucomatous diseases.

Considering that every adult should have an eye examination on a regular basis, even in the absence of refractive defects, it is a good idea to combine the examination with a blood pressure check (which is usually carried out), particularly when there are risk factors that can cause an increase in eye pressure.

After the age of 40, then, pressure undergoes a natural increase of about 1 mmHg every ten years, so it is even more important to have it measured after this age.

Eye pressure is one of the parameters that are examined to assess the health of the eyes.

It is important that the values fall within a range between 10-12 and 21-22 mmHg, because in the case of hypertension, damage to the optic nerve could occur and, consequently, glaucomatous disease could develop.

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