Ocular hypertension

What is ocular hypertension?

Ocular hypertension means that the intraocular pressure is higher than the normal value. However, this increased intraocular pressure does not yet have any harmful effects on the optic nerve or vision. This is why doctors do not yet classify ocular hypertension as a “disease”. However, increased intraocular pressure can lead to glaucoma, and the risk of glaucoma is increased with increased intraocular pressure. To be more precise: open-angle glaucoma. The optic nerve is then at risk and the damage cannot be reversed.

In ocular hypertension, two processes are no longer in balance: the outflow of aqueous humor in the chamber angle and its production in the ciliary body. When the fluid builds up in the eye, the intraocular pressure also increases. In most cases, this does not cause any symptoms and those affected do not notice it. Only when the optic nerve has suffered a great deal of damage do the first signs appear, such as visual disturbances and visual field loss.

It is not possible to say with certainty in whom the increased intraocular pressure will develop into glaucoma. In many cases, doctors initially observe ocular hypertension if there are no other risk factors for glaucoma. These include, for example, first-degree family members with glaucoma, severe short-sightedness or a thin cornea. You should have your eyes examined regularly by a doctor and have your intraocular pressure checked. Otherwise, ocular hypertension can be treated with medication that lowers the pressure in the eye. There are eye drops with different active ingredients.

Ocular hypertension – frequency and age

The frequency of ocular hypertension cannot be precisely quantified. This is because many sufferers do not feel the increased pressure in their eyes and therefore do not visit an ophthalmologist. Experts therefore suspect that the number of unreported cases is very high. Some facts and figures on glaucoma in Switzerland and worldwide:

• Experts estimate the risk of ocular hypertension developing into glaucoma at around ten percent within five years.
• Experts estimate that around 2.5 percent of all Swiss citizens over the age of 40 suffer from glaucoma. This risk doubles with every additional decade of age.
• Glaucoma affects around 70 million people worldwide – half of whom are unaware of their eye disease.
• In principle, anyone can develop glaucoma – even younger people. However, the risk of glaucoma increases from the age of 40.
• Glaucoma affects people of all genders and is one of the most common causes of blindness.

Ocular hypertension: causes

The cause of ocular hypertension is a disturbed outflow of aqueous humor or an increased production of this fluid. Both processes are out of balance. If the formation of aqueous humor is greater than the outflow, the intraocular pressure increases. The aqueous humor is important for the eye because the fluid keeps it in shape and supplies it with nutrients.

However, specialists only speak of ocular hypertension when the ocular eye pressure is more than 21 mmHg (millimeters of mercury). Normal intraocular pressure values are between 9 and 21 mmHg. Another characteristic of ocular hypertension is that there is no evidence of damage to the optic nerve or visual field defects.

In the long term, however, increased intraocular pressure can affect the optic nerve. This damage cannot be reversed. However, not every increased pressure in the eye necessarily leads to glaucoma.

Risk factors for glaucoma

Doctors are aware of a number of risk factors that can disrupt the production and drainage of aqueous humor and increase the risk of glaucoma. These include, for example:

• Elevated eye pressure values
• Genes
• older age
• familial predisposition – glaucoma in first-degree relatives
• Severe short-sightedness (more than -5 diopters) or severe long-sightedness
• Thin cornea – the thicker the cornea, the less likely it is that the ocular hypertension will develop into glaucoma
• Ethnicity – such as African or Asian origin
• Severe eye inflammation
• Eye injuries
• Complications caused by other eye diseases
• Previous eye operations
• certain underlying diseases: e.g. cardiovascular diseases or diabetes mellitus
• some medications, for example long-term treatment with cortisone

Symptoms: Ocular hypertension often goes unnoticed

Ocular hypertension does not cause any symptoms and therefore goes unnoticed for a long time. By definition, ocular hypertension does not yet involve damage to the optic nerve or visual field. Doctors often discover increased intraocular pressure by chance during a routine eye examination. For people over the age of 40, ophthalmologists recommend an eye examination every one to three years for the early detection of glaucoma. Eye examinations are advisable every two years from the age of 50 and every year from the age of 60.

The first symptoms usually appear when the ocular hypertension has progressed to glaucoma and the optic nerve has already suffered considerable damage. The following signs indicate this:

• impaired vision, e.g. blurred vision or loss of central visual acuity
• Visual field defects: Objects in the center of the visual field are clearly visible, while objects further out are no longer visible. Spatial perception is limited. Those affected often bump into objects or have problems climbing stairs or in traffic.
• Disorders of color vision
• Disorders of contrast perception
• Difficulties with light-dark adaptation

When these symptoms occur, the optic nerve is usually already damaged. And this damage cannot be undone. This is why it is so important to diagnose ocular hypertension as early as possible and then monitor it continuously with an ophthalmologist. This makes it possible to detect in good time whether the increased intraocular pressure could develop into glaucoma. If you have certain risk factors, doctors treat ocular hypertension preventively (prophylactically).

Ocular hypertension: Diagnosis with us

The diagnosis of ocular hypertension begins with a discussion of your medical history (anamnesis). The doctor will ask you a number of questions, including

• Have you noticed any symptoms? If yes: Which ones?
• When did the complaints first appear?
• How severe are the symptoms?
• Did they develop quickly or slowly and steadily?
• Do any family members have glaucoma?
• Do you have any known underlying diseases?
• Do you suffer from an eye condition, such as short-sightedness?
• Have you ever had an eye injury?
• Have you previously undergone eye surgery?
• Do you take medication or do you use it locally? If yes: Which and since when?
• Which ethnic group do you belong to?

Their answers already allow initial conclusions to be drawn about the cause of the symptoms. This is followed by various eye examinations. The most important are:

• Determination of visual acuity
• Slit lamp examination of the anterior and middle sections of the eye
• Ophthalmoscopy (fundoscopy, ophthalmoscopy): Examination of the back of the eye
• Tonometry – measurement of intraocular pressure, also at different times of day, to detect any fluctuations
• Perimetry: measurement of the visual field
• Gonioscopy: Examination of the chamber angle in the eye – an anatomical structure that lies between the cornea and the iris.

Sometimes further examinations follow, such as papillary photography or laser scanning tomography. These methods can be used to detect even the smallest changes in the optic nerve. Sometimes doctors examine how well the blood circulation is working. This is done, for example, by measuring blood pressure over 24 hours, capillary microscopy (reaction of the fine vessels to external stimuli such as cold) or a special ultrasound examination (sonography).

Ocular hypertension is present if the following criteria are met:

• The intraocular pressure is more than 21 mmHg (millimeters of mercury = unit of pressure). Doctors detect this increased intraocular pressure in one or both eyes.
• The optic nerve and visual field appear normal.
• There are no signs of eye disease – some eye diseases can be associated with increased intraocular pressure.

Ocular hypertension: prevention, early detection, prognosis

You cannot really prevent ocular hypertension. However, you have a number of options for early detection of increased intraocular pressure at the doctor’s surgery. Ophthalmologists recommend the following measures for early detection:

• If there is no known glaucoma in your family, a first ophthalmologic examination at the age of 40 is advisable. After that, you should repeat this every one to three years.
• An eye examination is recommended every two years from the age of one.
• After the age of one, it is best to have an eye examination once a year.

The situation is different if you have a family history of glaucoma. These recommendations apply here:

• If glaucoma is known to run in the family, all close relatives should be examined by an ophthalmologist as soon as possible. Ask your parents and siblings.
• If glaucoma has already occurred in your family members at a young age, the first examinations should take place from the age of 20.

In general, the probability of glaucoma increases with age.

Progression and prognosis of ocular hypertension

The course of ocular hypertension cannot be generally predicted. In some people, the increased intraocular pressure develops into glaucoma. Experts put the probability of this happening at just under ten percent within five years. However, doctors do not know for sure in advance who is affected.

It also depends on the individual risk factors that you bring with you. These include advanced age, significantly increased intraocular pressure, a family history of glaucoma, a thin cornea or severe short-sightedness. With treatment, the risk of the increased intraocular pressure developing into glaucoma within five years is reduced to around 4.4 percent.

If ocular hypertension has developed into glaucoma, the prognosis is less favorable. Glaucoma is associated with damage to the optic nerve that cannot be repaired. The consequences are impaired vision, loss of vision and, in the worst case, blindness.

Ocular hypertension: treatment often means waiting

In many cases, doctors wait before treating ocular hypertension. Based on the risk factors present, they estimate the probability that the increased pressure in the eye will lead to glaucoma. This must be prevented at all costs, as damage to the optic nerve cannot be reversed. In summary, this treatment strategy means: wait, observe and check the increased intraocular pressure at regular intervals. For example, intraocular pressure measurement, ophthalmoscopy, perimetry and other procedures are used.