What is ocular hypertension?
Ocular hypertension is an eye condition where the pressure within the eye or intraocular pressure is higher than that. Stress comes from a liquid called aqueous humor. It fills the space between the cornea, or the outer layer of the eye, and the lens at the front of the eye, which divides the front and back of the eye. The eye constantly produces aqueous humor and extracts it to nourish its tissues. Intraocular pressure can be very high if there is too much aqueous humor or it does not flow properly.
Ocular hypertension is not the same as glaucoma. The difference between ocular hypertension and glaucoma is damage to the optic nerve. In glaucoma, the optic nerve is not healthy, which can lead to vision problems and blindness.
On the other hand, ocular hypertension is an important risk factor for developing glaucoma. High intraocular pressure is one of the main causes of optic nerve damage and glaucoma. However, you can get glaucoma without ocular hypertension. And not all people with ocular hypertension will develop glaucoma. People with ocular hypertension need regular monitoring. If signs of damage appear, early intervention can help protect your vision.
Generally, ocular hypertension does not produce any symptoms, but it can be detected by a simple eye exam measuring it with a tonometer. To diagnose ocular hypertension, the results must be increased in one or both eyes in two different cases.
If you are African American, older than 40, or have a family history or glaucoma, your risk of developing high blood pressure is high. 4.5% of Americans over 40 have ocular hypertension. This rate increases to 7.7% at age 75.
Unfortunately, ocular hypertension is not curable, but it is treatable. If your ophthalmologist decides that treatment is needed, she may include eye drops to reduce the pressure inside the eye. In some cases, doctors may recommend laser treatment or surgery to reduce stress. Treatment can help reduce the risk of glaucoma and vision loss. However, this does not completely eliminate it. You still need regular checkups and eye exams.
Sometimes too much intraocular pressure can cause pain when moving or touching the eyes. Seek medical attention immediately if you experience this.
Symptoms of ocular hypertension
Ocular hypertension in most cases has no signs or symptoms. This means that you may have increased intraocular pressure and may not notice it, and this could put your vision at risk if you continue to develop glaucoma. Therefore, it is important to follow the guidelines for general eye care.
During a comprehensive eye exam, doctors measure intraocular pressure with a device called a tonometer. There are a few different versions of this tool. A common one is to use a puff of air to briefly flatten the cornea. The amount of flattening tells your doctor about the pressure inside your eye.
You should have a baseline eye exam at age 20 and see your ophthalmologist twice at age 30. Once you turn 40, you should have a comprehensive eye exam, and your doctor will use the results to tell you how often to return. If you have a family history of ocular hypertension or glaucoma, these guidelines may change. Talk to your ophthalmologist to find out how often you should get tested.
In some cases, people may experience symptoms when the intraocular pressure is too high. It is usually accompanied by pain with movement or touch of the eyes. See your ophthalmologist as soon as possible if you have these symptoms.
Causes of ocular hypertension
The eyebrows are not empty organs. They have two types of liquid-vitreous humor, which fill the eye from the lens to the retina and aqueous humor that fills the area in front of the lens. In general, the eye constantly produces new aqueous humor and removes old fluid. Ocular hypertension occurs when there is excess aqueous humor in the front of the eye.
This can be the result of excessive fluid production or improper drainage. The reason why any of these problems occurs is unclear.
Elevated intraocular pressure is a concern in people with ocular hypertension because it is one of the main risk factors for glaucoma.
High pressure inside the eye is caused by an imbalance in the production and drainage of fluid in the eye (aqueous humor). The channels that normally drain the fluid from inside the eye do not function properly. More fluid is continually being produced but cannot be drained because of the improperly functioning drainage channels. This results in an increased amount of fluid inside the eye, thus raising the pressure.
Another way to think of high pressure inside the eye is to imagine a closed, nonexpandable water container. The more water that is put into the container, the higher the pressure inside the container. The same situation exists with too much fluid inside the eye — the more fluid, the higher the pressure. The optic nerve in the eye can be damaged by too high of a pressure.
Risk factors for ocular hypertension
Many factors increase the risk of developing ocular hypertension. However, not all people with risk factors develop ocular hypertension. Risk factors:
- African American or Hispanic heritage
- 40 years or more
- Some medical conditions, such as diabetes and high blood pressure
- Conditions such as eye injuries, surgery, and severe myopia and pigmentation syndrome
- Family history of ocular hypertension or glaucoma
- Long-term use of corticosteroid medications
- Lowers your risk of blood pressure
Many risk factors for ocular hypertension are beyond your control. You cannot change your genetics. However, if you have medical conditions that increase your risk, there are steps you can take to reduce your risk. Controlling blood sugar, blood pressure, and other eye conditions can help to prevent ocular hypertension.
If you have any risk factors for ocular hypertension, see your ophthalmologist every day. The only way to know if you have high intraocular pressure is through a comprehensive eye exam that includes tonometry.
Diagnosis of ocular hypertension
An ophthalmologist will perform tests to measure eye pressure and to rule out early primary open-angle glaucoma or secondary causes of glaucoma. These tests are described below.
Your visual acuity, which indicates how well you can see an object, is initially assessed. Your ophthalmologist will determine your visual acuity by reading the letters across the room using an eye chart. This is usually done with the glasses that best correct your vision.
The front of the eyes, including the cornea, anterior chamber, iris, and lens, are examined with a special microscope called a slit lamp.
Tonometry is a method used to measure the pressure within the eye. Measurements are taken for both eyes in two or three cases before making an accurate diagnosis of ocular hypertension. Intraocular pressure varies from hour to hour in any person, and measurements can be taken at different times of the day (for example, in the morning and in the evening). A pressure difference between two eyes of 3 mm Hg or more indicates that further evaluation is needed. Early open-angle primary glaucoma is more likely if intracellular pressure increases gradually.
Each optic nerve is examined for damage or abnormalities; Students must be dissected with eye drops to ensure proper examination of the optic nerve. A normal optic nerve consists of a scooped or hollowed optic nerve. Large optic nerve cups, cup asymmetry between two optic nerves, or progressive cup dilation indicates a glaucomatous change.
Pictures of your optic disc (the front surface of your optic nerve) Pictures taken for future reference and comparison.
Gonioscopy is done to check the drainage angle of your eye; To do this, a special contact lens is placed over the eye. This test is important to know if the angles are open, narrow or closed and to rule out other conditions that may increase intraocular pressure.
Visual field tests check your peripheral (or side) vision, usually by using an automated visual field machine. This test is done to rule out visual field defects due to glaucoma. Visual field tests may need to be repeated. If the risk of glaucomatous damage is low, testing can only be done once a year. If the risk of glaucomatous damage is high, testing should be done frequently once every two months.
Pachymetry (or thickness of the cornea) is verified with an ultrasound probe to determine the accuracy of intraocular pressure readings. A thin cornea can give low pressure readings erroneously, while a thick cornea can give false high pressure readings.
Imaging of the nerve fiber membrane and the ganglion cell membranes of the optic nerve and the retina using optical coherence tomography (OCT) is a new technique that is fast, painless, and targeted. It can detect early changes in structure, suggesting that ocular hypertension treatment is needed to prevent glaucoma.
Treatment for ocular hypertension
Whether ocular hypertension needs treatment or not depends on your risk of developing glaucoma. For those at low risk, it is advisable to monitor eye pressure and optic nerve health on a daily basis. In high-risk individuals, treatment of ocular hypertension increases the risk of glaucoma by more than 50%.
The therapeutic goal is to restore intraocular pressure within the normal range. It is usually used in the form of eye drops:
Alpha agonists such as apraclonidine (Iopidine) and brimonidine (Alphagan-P)
Beta-blockers, betaxolol (betoptic), levobunolol (betagon), and timolol (timoptic)
Carbonic anhydrase inhibitors, brinzolamide (Azopt) and dorzolamide (TruSopt)
Prostaglandin agonists, bimatoprost (Lumigan), latanoprost (Jalatan), and travoprost (Travaton)
Rho kinase / norepinephrine transporter inhibitors such as netarsudil (Ropressa)
There are also many combination products available that use two different classes of drugs. In some cases, doctors recommend the use of laser therapy or surgery to reduce eyestrain.
The goal of medical treatment is to reduce the pressure before it causes glaucomatous loss of vision. Medical treatment is always initiated for those people who are believed to be at the greatest risk for developing glaucoma (see When To Seek Medical Care) and for those with signs of optic nerve damage.
How your eye doctor chooses to treat you is highly individualized. Depending on your particular situation, you may be treated with medications or just observed. Your doctor will discuss the pros and cons of medical treatment versus observation with you.
Some eye doctors treat all elevated intraocular pressures of higher than 21 mm Hg with topical medicines. Some do not medically treat unless there is evidence of optic nerve damage. Most eye doctors treat if pressures are consistently higher than 28-30 mm Hg because of the high risk of optic nerve damage.
If you are experiencing symptoms like halos, blurred vision, or pain, or if your intraocular pressure has recently increased and then continues to increase on subsequent visits, your eye doctor will most likely start medical treatment.
Your intraocular pressure is evaluated periodically using guidelines similar to these:
If your intraocular pressure is 28 mm Hg or higher, you are treated with medicines. After 1 month of taking the drug, you have a follow-up visit with your eye doctor to see if the medicine is lowering the pressure and there are no side effects. If the drug is working, then follow-up visits are scheduled every 3-4 months.
If your intraocular pressure is 26-27 mm Hg, the pressure is rechecked in 2-3 weeks after your initial visit. On your second visit, if the pressure is still within 3 mm Hg of the reading at the initial visit, then follow-up visits are scheduled every 3-4 months. If the pressure is lower on your second visit, then the length of time between follow-up visits is longer and is determined by your eye doctor. At least once a year, visual field testing is done and your optic nerve is examined.
If your intraocular pressure is 22-25 mm Hg, the pressure is rechecked in 2-3 months. At the second visit, if the pressure is still within 3 mm Hg of the reading at the initial visit, then your next visit is in 6 months and includes visual field testing and an optic nerve examination. Testing is repeated at least yearly.
Are there home remedies for ocular hypertension?
If your ophthalmologist prescribes it to help reduce the pressure inside your eye (see Medical Treatment and Medications for use), it is important to apply the medication correctly and follow your doctor’s instructions. Failure to do so will further increase intraocular pressure, leading to optic nerve damage and permanent vision loss (for example, glaucoma).
Complications of ocular hypertension
The main problem with ocular hypertension is glaucoma, or damage to the optic nerve. Glaucoma causes vision problems and is one of the leading causes of blindness in the elderly. However, not all people with ocular hypertension develop glaucoma. If you have ocular hypertension, the risk factors for developing glaucoma are:
- Bleeding in the head of the optic nerve
- Family history of glaucoma
- Excess intraocular pressure
- Low ocular perfusion pressure
- Think central cornea
- Many of these risk factors can only be determined with a comprehensive eye exam. Talk to your doctor about your risk category to understand your personal potential for developing glaucoma.
- Remember, treating ocular hypertension reduces the risk of glaucoma, but it does not eliminate it. It is important to continue regular eye exams throughout your life.