The term hypertension typically refers to high blood pressure. In the realm of optometry and ophthalmology, ocular hypertension refers to a buildup of fluid pressure inside the eye. Just as high blood pressure must be managed well to support whole-body health, ocular hypertension requires immediate diagnosis and treatment to support eye and vision health.
What Is Ocular Hypertension?
Your eye is dependent on two different types of fluid: aqueous humor and vitreous humor. The vitreous humor lives in the deeper parts of the eyeball. It is a thicker fluid and provides structural support to the eyewall, protects the eye from impact, and also helps to keep the retina in place. The aqueous humor is found in chambers located in both the front and back (anterior and posterior) of the eye.
The aqueous humor’s job is to regulate pressure in the eye. Aqueous humor is more liquidy and in addition to regulating pressure in the outer part of the eye, it supplies nutrients to the parts of the eye that don’t have a direct connection to a blood supply, and the aqueous humor also washes away debris and toxins from the eye.
The body makes aqueous humor and flushes it into the eye at the same rate that it drains it out again. If the eye makes more aqueous humor than it flushes, there is a high-pressure build-up and we call this ocular hypertension. If the condition isn’t diagnosed, and the high pressure persists, it can damage the optic nerve and puts you at a much higher risk for developing glaucoma. In fact, the American Academy of Ophthalmology (AAO) describes those with ocular hypertension as being “glaucoma suspects.”
Risk Factors Include…
While anyone can potentially develop ocular hypertension, there are several risk factors that increase your chances:
- A family history of the condition
- People with diabetes or high blood pressure
- Being 40-years old or older (As a result of The Ocular Hypertension Treatment Study estimates that between 4.5% and 9.4% of Americans 40+ have ocular hypertension)
- Having extreme myopia (nearsightedness)
- African-Americans and Latin Americans/Hispanics
- Those who’ve had eye surgery or eye injuries in the past
- Having pigment dispersion syndrome or pseudoexfoliation syndrome (PXF)
- Taking long-term steroid medications
If any of these are true for you, speak to your optometrist about more frequent eye exams.
Annual eye exams are crucial for diagnosis
Unlike other eye conditions such as cataracts or the development of astigmatism, there are no clear symptoms of ocular hypertension. It requires a full eye exam, where your eye doctor checks your intraocular pressure (IOP) to uncover ocular hypertension. This is just one reason why annual eye exams are so important.
During the exam, your eye doctor will use drops that temporarily numb the surface of your eye. Then, s/he’ll use one of several standard tests that can measure the pressure in the eye. These include:
- Applanation tonometry. For this test, in addition to the numbing drops, the doctor also adds a non-toxic dye into the eyes. Then, you’ll sit in front of a piece of equipment that has a lamp and a small probe with a tip that gently presses the exterior of your eye to measure the resistance or pressure.
- Pneumotonometry. This is the method we use if a patient has scarred corneas. No dye is used for the pneumotonometry measurement. This version creates a printout and is thought to be less affected by variations in corneal thickness.
- Rebound tonometry. We use a small probe with a rubber end to gently bounce the tip on the exterior of the cornea. This can be off-putting for some patients because you can see the tip coming in towards the eyes. Other patients find it fascinating because you can’t feel a thing.
- Air-puff tonometry. Like applanation tonometry, you’ll be seated at a sit lamp, but in between blinks we’ll direct a quick puff of air at your cornea, during which the machine measures the IOP.
An eye pressure reading of 21 mmHg (millimeters of mercury) or higher generally signifies ocular hypertension.
Causes & treatment for ocular hypertension
Beyond the risk factors associated with ocular hypertension (listed above), several factors ultimately cause the condition.
- Excessive aqueous production. If your eyes produce more aqueous humor than they can drain properly, it will cause a buildup of pressure.
- Poor drainage. On the other side of the equation, if there is an issue with how your eye drains the aqueous humor, this will also cause high aqueous pressure. Usually, aqueous liquid drains from the eye through the trabecular meshwork, which is found around the sides of the rear chamber of the eye. Any disruption to the trabecular meshwork and its correlating parts can slow down drainage.
- Certain medications. Certain medications, especially steroid medications, put you at higher risk for developing ocular hypertension. This is why it’s so important to provide a detailed account of your medical history and medication usage. Your eye doctor will take special care to look out for higher-than-normal pressure in your eyes. Even the steroid drops prescribed after LASIK and other eye surgeries can cause temporary pressure changes, which your doctor knows to look out for.
- Eye injury or trauma. It can take months or even years for ocular hypertension to occur after an eye injury or trauma. So, make sure to let your optometrist know if you have ever had a serious injury to your eye, even if it feels far back in the past.
- Other eye issues. Other issues affecting eye health, such as pigment dispersion syndrome, corneal arcus, and pseudoexfoliation syndrome can also be precursors to developing ocular hypertension.
Treatment varies from patient to patient
Whether or not we treat ocular hypertension depends on a variety of factors. Sometimes, the condition can be controlled with eye drops or other medications. However, all medications come with certain side effects.
So, if your IOP is only slightly higher than normal, we typically take a watch and wait approach to minimize unnecessary intervention. If we feel your ocular hypertension is under control, we may not do anything at all other than have you come in more frequently for checkups and to keep an eye on the development of glaucoma.
If your pressure readings are in the higher range, we’ll probably prescribe drops that bring that pressure down. Patients who don’t respond to the drops and are showing signs of glaucoma will have other treatment options available.
The best way to prevent ocular hypertension is to eat well and exercise (minimizing your risk of diabetes or high blood pressure) and to make sure you have your eyes thoroughly examined at least once every year.
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