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  • Writer's pictureCarina Lee

Why Is Eye Pressure Important?

Dr. Carina Lee, August 15, 2022

Have you heard your ophthalmologist refer to "eye pressure" but are unsure of what it means?

The fluid pressure inside the eye is referred to as eye pressure, commonly known as intraocular pressure (IOP). Your eyesight will be preserved and you can avoid losing your vision from eye illnesses like glaucoma, an eye disease that can cause blindness, by maintaining a healthy IOP.

How is IOP measured?

Your eye doctor will use a tonometry test as part of a complete eye examination to measure your IOP and identify any changes in your eye pressure. A rise in eye pressure can harm the optic nerve and raise your chance of developing glaucoma.

Types of tonometry tests

Goldmann applanation tonometry test.

As it is thought to be the most accurate method of determining IOP, this test is the most frequently performed. Your eye doctor will provide numbing drops to your eyes prior to the test to ensure that you don't experience any pain. A non-toxic dye drop will be placed on your lower eyelid once your eyes have become numb. For proper illumination and eye magnification, you will then sit with your head in a slit lamp apparatus. In order to flatten a little portion of your cornea, your eye doctor will gently touch the surface of your eye. The amount of pressure required to flatten your cornea will be used to determine your eye pressure..

Air-puff tonometry, a non-contact tonometry technique. In contrast to the Goldmann applanation test, this procedure flattens a small portion of your cornea with a brief air pulse.

Tonometry in rebound. In order to assess your eye's reaction to the touch, you will place a tiny probe on your cornea and move it slightly during this exam. This type of test can be performed in the comfort of your home using some equipment, such as the iCare gadget, which is portable and doesn't require numbing drops.

Another portable instrument, the tonometer or tonopen, measures your IOP by contacting your cornea and analyzing the indentation. But before the test is done, this instrument needs numbing drops.

Does eye pressure remain constant throughout the day?


Eye pressure varies throughout the day and is often highest in the morning, which is crucial to understand. A little estimate of your usual IOP can therefore only be obtained by measuring your ocular pressure during an examination. Additionally, if you have glaucoma, a change in IOP levels during the day might be harmful to the health of your eyes. The optimum strategy to monitor your IOP, whether at home or during more frequent eye exams, should be discussed with your eye doctor. When scheduling your next examination, keep in mind that eye physicians typically advise measuring ocular pressure in the morning.

What causes an increase in eye pressure?

Aqueous humor, or fluid, flows continually through a healthy eye.

Eye fluid is in charge of:

  • Lubricating the muscles and fibers of the focusing lens

  • Supplying nutrients and oxygen to the back of the cornea

  • Clearing away waste products from the cornea

  • Maintaining the shape of the cornea

Previous fluid drains out of the eye through the anterior angle, where the cornea and iris meet, while fresh fluid is created. The fluid travels from the eye to the trabecular meshwork, uveoscleral drains, and back of the nose. To keep IOP at normal levels, this drainage system must stay unobstructed and functional. If a problem develops and the fluid can no longer drain effectively, a buildup of fluid may happen, which can subsequently increase ocular pressure.

What happens when eye pressure remains high?

If your IOP stays high—between 15 and 25 mmHG—for a long time without receiving therapy, the pressure will steadily exert pressure on the optic nerve, harming it and ultimately resulting in permanent vision loss. Sometimes an increase in IOP happens abruptly, immediately going above 30 mm HG or even 40 mm HG. Angle-closure glaucoma and eye trauma are the main causes of this, and it can cause serious optic nerve damage without any prior warning.

It's crucial to realize that variations in eye pressure do not hurt and may go unnoticed for years while gradually impairing eyesight.

Therefore, a tonometry test is essential for spotting early indications of elevated eye pressure or ocular issues that could raise your risk of developing glaucoma. Your chances of preventing vision loss and/or keeping remaining vision are higher the earlier the condition is identified.

When should I have a tonometry test?

Annual eye exams include tonometry testing, although for the following reasons, it may be done more frequently:

  • If you are experiencing symptoms that may indicate a change in IOP

  • If you are taking steroid medication post cataract surgery or for any other medical reason

  • If you are at risk of glaucoma

  • If you have been diagnosed with, or are at risk of developing iritis or retinal detachment

Which symptoms are associated with high IOP?

Numerous symptoms can be indicative of excessive IOP, however they might also be brought on by another ocular problem. In order to rule out glaucoma, your eye doctor will do a tonometry test if you have any of the symptoms listed below:

  • Severe pain

  • Redness

  • Blurred vision

  • Halos around lights

  • Gradual peripheral vision loss

  • Tunnel vision

If you experience any of these symptoms contact an eye doctor near you.

Who is at risk of developing glaucoma?

A tonometry test will be performed if your risk of developing glaucoma is higher to look for any changes in your IOP.

Typical risk elements include:

  • Over 60 years of age

  • African American or Hispanic race

  • Family history of glaucoma

  • Diabetes

  • Hypothyroidism

  • Chronic ocular conditions

  • Eye injuries

  • Myopia

  • Extended use of steroid medication

What is considered a normal eye pressure?

The average ocular pressure is 12 to 22 millimeters of mercury (commonly presented as mm Hg).

In most circumstances, if your IOP is more than 20 mm Hg, you may already have glaucoma or be at risk of getting it.

Even with a normal IOP, glaucoma can occasionally develop, which emphasizes the value of routine eye exams for spotting any changes to your vision or ocular health.

Your eye doctor will consider other relevant aspects in order to properly diagnose an optical ailment in some circumstances when high IOP might develop after an eye injury, blood vessel inflammation, or other ocular disorders.

If you may be at risk for having a high IOP or have a family history of glaucoma, or may be at risk of high IOP. Contact your eye doctor to help determine the most effective way to control your eye pressure and reduce the risk of glaucoma.

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