Why Is Eye Pressure Important?

Have you ever heard an optometrist talk about ‘eye pressure’ and found yourself uncertain about its meaning?

The term “eye pressure,” or intraocular pressure (IOP), describes the pressure from fluids within the eye. Keeping eye pressure at a healthy level is crucial for protecting your sight and avoiding vision impairment caused by conditions like glaucoma, a serious eye disorder that can lead to loss of vision.

How is IOP measured?

In the course of a thorough eye examination, your optometrist will carry out a procedure known as a tonometry test to assess the pressure within your eye, also referred to as IOP, to identify any shifts that could signal a problem. Elevated eye pressure is a concern because it can harm the optic nerve and heighten the likelihood of developing glaucoma.

Here’s a breakdown of the different tonometry tests used:

  • The Goldmann applanation tonometry test is widely regarded as the gold standard for measuring eye pressure due to its accuracy. During this test, after applying numbing drops to eliminate any discomfort, your doctor will also use a harmless dye on your lower eyelid. You’ll then position your head into a slit lamp, which provides the necessary illumination and magnification of your eye. The doctor measures your eye pressure by lightly pressing on your eye to flatten a part of the cornea, with the pressure needed for this action indicating your IOP.

    • Non-contact tonometry or air-puff tonometry works on a principle similar to the Goldmann test but uses a burst of air to achieve the corneal flattening.

    • Rebound tonometry involves a small probe touching your cornea and measuring how your eye responds. Tools like the iCare device make this method more accessible since it’s portable, doesn’t require numbing drops, and can even be used at home.

    • The tonometer or tonopen, another portable device, assesses your IOP by making contact with your cornea and measuring its indentation, necessitating numbing drops for comfort.

    These tests are instrumental in monitoring eye health, particularly in preventing conditions like glaucoma by keeping an eye on the intraocular pressure.

Does eye pressure remain constant throughout the day?


Eye pressure doesn’t stay the same all day. It’s crucial to recognize that your eye pressure can fluctuate over the course of a day, typically reaching its peak in the morning. As a result, the measurement taken during an eye examination is just a snapshot of your typical intraocular pressure (IOP).

Additionally, variations in IOP throughout the day can pose a risk to your eye health, particularly if you’re dealing with glaucoma. It’s essential to have a conversation with your optometrist about the most effective strategy for monitoring your IOP, whether that means doing it yourself at home or opting for more regular check-ups. Generally, optometrists suggest measuring eye pressure in the morning, so it’s wise to keep this in mind when planning your next appointment.

What causes an increase in eye pressure?

In a functioning eye, there’s a continuous flow of aqueous humor, or eye fluid, which plays several vital roles. It not only lubricates the muscles and fibers that aid in lens focusing but also delivers nutrients and oxygen to the cornea’s backside, removes waste products from the cornea, and helps keep the cornea’s shape intact.

This eye fluid is constantly being replenished, and as new fluid comes in, the old fluid exits through the anterior angle of the eye, the point where the iris meets the cornea. From there, the fluid is directed to the uveoscleral drains and the trabecular meshwork, eventually making its way down to the back of the nose and throat.

For eye pressure to stay within a normal range, this drainage system needs to function properly. If there’s a glitch in this system, preventing the fluid from draining as it should, it can lead to a buildup of fluid. This buildup is what causes an increase in eye pressure, and maintaining a clear, unobstructed drainage path is crucial for preventing such issues.

What happens when eye pressure remains high?

When eye pressure remains elevated, within the range of 15-25 mmHg, over a prolonged period without intervention, it exerts continuous pressure on the optic nerve. This sustained pressure can lead to optic nerve damage, resulting in irreversible vision loss.

In certain situations, eye pressure can spike suddenly, soaring above 30 mmHg or even reaching 40 mmHg. This sudden increase is often due to conditions like angle-closure glaucoma or an injury to the eye, posing a significant risk of severe optic nerve damage without prior symptoms.

It’s crucial to recognize that changes in eye pressure typically don’t cause pain, meaning they can easily go undetected for extended periods while gradually impairing your vision.

That’s why undergoing a tonometry test is essential for identifying early signs of elevated eye pressure or any eye conditions that could increase your risk of developing glaucoma. Early detection of such conditions significantly improves the chances of preventing or limiting vision loss and preserving your sight.

It’s advisable to book an eye examination with an optometrist who specializes in the diagnosis and management of glaucoma to safeguard your eye health.

When should I have a tonometry test?

Tonometry tests are a standard part of yearly eye examinations but might be performed more often for several reasons, including:

  • Experiencing symptoms that suggest a change in your eye pressure.
  • Taking steroid medications following cataract surgery or for other medical purposes.
  • Being at a higher risk for developing glaucoma.
  • Having a diagnosis or a higher risk for conditions like iritis or retinal detachment.

When it comes to high IOP, various symptoms could signal its presence, yet these symptoms might also be linked to other eye problems.

If you notice any of the symptoms below, your optometrist will likely conduct a tonometry test to exclude the possibility of glaucoma:

  • Intense pain in the eye
  • Eye redness
  • Vision becoming blurred
  • Seeing halos around lights
  • Losing peripheral vision gradually
  • Experiencing tunnel vision

Should you experience any of these symptoms, it’s advisable to consult an eye care professional promptly.

Concerning the risk factors for glaucoma, a tonometry test is crucial for those with an increased chance of developing the condition. Key risk factors include:

  • Being over 60 years old.
  • Having African American or Hispanic heritage.
  • A family history of glaucoma.
  • Diabetes.
  • Hypothyroidism.
  • Suffering from chronic eye conditions.
  • Previous eye injuries.
  • Myopia (nearsightedness).
  • Long-term use of steroid medications.

What is considered a normal eye pressure?

A typical range for healthy eye pressure falls between 12 and 22 mm Hg (millimeters of mercury). Generally, an IOP reading over 20 mm Hg might indicate a potential risk for glaucoma or that the condition is already present.

It’s worth noting that glaucoma can sometimes develop even when eye pressure is within this normal range, underscoring the significance of regular eye examinations to monitor for any shifts in eye health or vision.

Elevated eye pressure can also result from an eye injury, inflammation of blood vessels, or various other eye issues. In such instances, your eye specialist will consider additional factors to accurately diagnose any eye conditions.

For those with a family history of glaucoma or individuals who might be prone to higher IOP, scheduling a consultation with an eye care professional is advisable to explore the best strategies for managing eye pressure and minimizing the risk of glaucoma.