What is Intraocular Pressure (Eye Pressure)?

Intraocular pressure (IOP), also known as eye pressure or high eye pressure, refers to the pressure exerted on the inner wall of the eye.

Increased eye pressure is caused by an imbalance in the production or drainage of aqueous humor. Regular check-ups with an ophthalmologist are important since symptoms are rarely consciously perceived.

What is Normal Eye Pressure?

Eye pressure, also called intraocular pressure (IOP), is the physical pressure exerted on the inner wall of the eye. It is influenced by the balance between the production and drainage of aqueous humor.

Normal eye pressure ranges between 10 and 21 mmHg, with the average value being around 15.5 mmHg. mmHg stands for millimetres of mercury and is a medical measurement for the pressure of bodily fluids.

Many people wonder what is intraocular pressure. High intraocular pressure, also known as ocular hypertension, does not always have a pathological cause and is not a disease by itself. However, it is crucial to investigate the cause in detail, as high eye pressure can indicate or be a symptom of a systemic disease that requires treatment.

Additionally, elevated eye pressure should be monitored as it can lead to glaucoma. This condition damages the optic nerve, potentially causing irreversible vision damage.

What Happens with Increased Pressure Within The Eye?

Increased eye pressure occurs when the drainage of aqueous humor is impaired or its production is elevated. The two processes become unbalanced, leading to more aqueous humor being produced than can be drained, thus increasing eye pressure. When it exceeds 21 mmHg, it is called ocular hypertension.

It is important to examine what is normal eye pressure. A key characteristic of normal eye pressure is that no visual function impairments, such as visual field defects or optic nerve damage, have occurred.

If high eye pressure increase persists over a long period, it can cause irreversible optic nerve damage, leading to glaucoma. Aqueous humor plays a vital role in the eye, maintaining its shape and supplying the lens and cornea with essential nutrients.

Eye pressure is measured using a procedure called tonometry, employing a device called a tonometer. There are several different methods for tonometry, with the two most common being non-contact tonometry and Goldmann applanation tonometry.

Goldmann Applanation Tonometry

The eye is anaesthetised with eye drops to perform the examination painlessly. A sensor then flattens a small area of the cornea. The pressure needed for this corresponds to the intraocular pressure and can be read by the doctor. Goldmann applanation tonometry is a highly accurate method for measuring eye pressure.

Non-Contact Tonometry

A brief puff of air flattens the cornea, and the resulting corneal deformation is measured to determine the intraocular pressure. This method is only effective up to a certain pressure level; it becomes unreliable with significantly elevated eye pressure.

Symptoms of High Eye Pressure

Most people with high eye pressure do not experience symptoms. The intraocular pressure can rise slowly over a long period, making changes go unnoticed. Therefore, doctors and opticians recommend annual medical check-ups with an ophthalmologist, which include eye pressure measurement.

The following symptoms may occur in individuals with acutely elevated eye pressure:

• Pressure behind the eye: An uncomfortable pressure around and behind the eye can indicate high intraocular pressure. However, this pressure sensation can also result from inflammation of the eyelid edges, conjunctiva, or cornea.
• Headaches: Severe headaches and eye pain, often affecting only one eye, along with visual disturbances, nausea, and vomiting, can indicate acute glaucoma. This is a medical emergency requiring immediate attention.
• Burning Eyes: Burning and red eyes may also signal acutely elevated eye pressure.

In the presence of these symptoms, it is advisable to consult an ophthalmologist immediately. Once symptoms such as reduced vision or visual field defects appear, irreversible optic nerve damage has often already occurred.

Causes of Eye Pressure

As mentioned, increased eye pressure does not always have a pathological cause, but identifying the cause is essential to implement appropriate treatment. Below are risk factors and causes of elevated eye pressure. People at higher risk should regularly consult with an ophthalmologist to determine the frequency of their check-ups.

• Age: From age 40, annual eye pressure checks are recommended. Older individuals are more frequently affected by high eye pressure.
• Genetics: If elevated eye pressure or glaucoma is known or prevalent in your family, regular eye pressure checks are worthwhile. Ethnic factors can also play a role; people with darker skin are more frequently affected.
• Blood Pressure: Although blood pressure is not directly related to eye pressure, chronic or acute high blood pressure can cause vascular calcification and circulation disorders, affecting the eyes. High blood pressure increases the risk of vascular occlusions and nerve fibre layer damage, potentially causing permanent vision impairment and blindness. People with low blood pressure should also undergo regular checks, as low blood pressure can reduce blood flow and nutrient/oxygen supply, especially at night.
• Pre-existing Conditions: Heart and circulatory diseases (e.g., arteriosclerosis) and diabetes mellitus can lead to increased eye pressure. Individuals with migraines also have a lower risk of elevated eye pressure.
• Severe Refractive Errors: Significant refractive errors with changes in eye tissue, such as high myopia or hyperopia, can also pose a higher risk for increased eye pressure.
• Acute Eye Inflammation or Trauma: Severe acute eye inflammation or previous eye trauma can lead to elevated eye pressure.
• Medications: Long-term use of corticosteroid medications can increase eye pressure, potentially damaging the optic nerve or causing lens clouding, leading to cataracts or glaucoma.

Risks of High Eye Pressure

High eye pressure is often detected late since symptoms usually appear only after damage has occurred. Increased pressure in the eye can cause irreversible optic nerve damage. The first signs are often reduced vision and visual field defects, indicative of glaucoma.

Treatment for High Eye Pressure

There are different types of increased intraocular pressure treatments available. For ocular hypertension, the treatment approach is often watchful waiting. Monitoring and regularly checking eye pressure is essential to detect and treat glaucoma early. Therapy aims to normalise and maintain eye pressure within the normal range, using various methods:

• Medication: Primarily, medications are prescribed to reduce aqueous humor production or improve its drainage, available as eye drops or tablets.
• Laser Therapy or Surgery: If medication is insufficient, laser therapy or surgery may be the next step, also aimed at improving aqueous humor drainage or reducing its production.
• If another disease underlies the eye pressure, a suitable, individualised treatment method is chosen.

How to Prevent High Eye Pressure

There are no direct measures to prevent an increase in eye pressure. However, risk factors can be minimised: a healthy lifestyle, avoiding smoking, and maintaining good blood pressure can reduce the risk of heart and circulatory diseases that can lead to increased eye pressure.

While glaucoma itself cannot be prevented, regular check-ups with an ophthalmologist are crucial if certain risk factors or causes apply to you. Early detection through screening can help diagnose and treat underlying conditions promptly.

Preventive measures include reducing risk factors for high eye pressure: a healthy lifestyle with a balanced diet and sufficient exercise, no smoking, and maintaining good blood pressure can lower the risk of developing heart and circulatory diseases.