What is Ocular Hypertension (High Eye Pressure)?
The pressure inside the eyeball is called intraocular pressure. In normal physiological condition, fluids enter the eyeball to supply nourishment and maintain the shape of the eye. Sometimes, a dysfunctional eye drainage system causes the fluid to build up, resulting in an increase in pressure inside the eye, which is known as ocular hypertension. A chronically higher intraocular pressure (>21 mmHg) often leads to the development of glaucoma – an eye disorder wherein persistently high eye pressure damages the optic nerve and causes vision loss. Unlike glaucoma, ocular hypertension is usually asymptomatic and not directly related to optic nerve damage and vision loss. Researchers have estimated that ocular hypertension is 10 to 15 times more likely to occur than primary open-angle glaucoma, the most common type of glaucoma.
How Do You Know You Have Ocular Hypertension?
You can’t tell by yourself that you have ocular hypertension, because there are no outward signs such as eye pain or red eyes. During a comprehensive eye exam, your eye care practitioner will measure your IOP and compare it with normal levels.
5 Causes of Ocular Hypertension
The eye constantly makes a clear fluid called aqueous humor, which enters the front section of the eye to supply nutrition. An equal amount of fluid also flows out simultaneously to maintain a normal eye pressure. When this drainage system fails to function properly, the fluid accumulates and intraocular pressure increases, leading to ocular hypertension.
Factors that cause or are associated with ocular hypertension are virtually the same as the causes of glaucoma. These include:
Excessive aqueous production. The aqueous (or aqueous humor) is a clear fluid that is produced in the eye by the ciliary body, a structure located behind the iris. The aqueous flows through the pupil and fills the anterior chamber of the eye, which is the space between the iris and the cornea.
The aqueous drains from the eye through a structure called the trabecular meshwork, in the periphery of the anterior chamber, where the cornea and iris meet. If the ciliary body produces too much aqueous, the pressure in the eye increases, causing ocular hypertension.
Inadequate aqueous drainage. If the aqueous drains too slowly from the eye, disrupting the normal balance of production and drainage of the eye’s clear fluid, this too will cause high eye pressure.
Certain medications can have the side effect of causing ocular hypertension in certain individuals. Steroid medicines used to treat asthma and other conditions have been shown to increase the risk for ocular hypertension.
Even steroid eye drops used after LASIK and other refractive surgery can cause high eye pressure in susceptible individuals. If you have been prescribed steroid medications for any reason, consult with your eye doctor to see how frequently you should have your IOP checked.
Eye trauma. An injury to the eye can affect the balance of aqueous production and drainage from the eye, possibly leading to ocular hypertension.
Sometimes this can occur months or years after the injury. During your routine eye exams, be sure to mention to your doctor if you have experienced any recently or in the past.
People with certain diseases, such as diabetes or high blood pressure, or people who are very nearsighted (myopic) are more susceptible for developing ocular hypertension. In addition, people with pigment dispersion syndrome (an eye disorder that occurs when pigment cells of the iris float in the aqueous humor) and exfoliation syndrome (an eye disorder caused by an accumulation of abnormal fibrillar extracellular material in the ocular tissues) are at risk. A family history of ocular hypertension or glaucoma is also a major risk factor.
Interestingly, although systemic hypertension (high blood pressure) increases the risk of ocular hypertension, a low blood pressure can cause glaucoma by reducing ocular perfusion pressure and blood supply to the eye and optic nerves.