viernes, 8 de marzo de 2019

What Causes Ocular Hypertension?

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By Sanchari Sinha Dutta, Ph.D.Reviewed by Jennifer Logan, MD, MPH

Ocular hypertension is a condition wherein the internal pressure of the eye becomes higher than the normal.

What is ocular hypertension?

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 (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.

It is known from scientific findings that about 10% of people with untreated ocular hypertension develop primary open angle glaucoma in 5 years. Therefore, a regular monitoring of the eye pressure is important for these people to avoid the possibility of developing glaucoma.

What causes 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.

In most cases, a blockage in the drainage channels of the eye or overproduction of aqueous humor is responsible for ocular hypertension. In addition, injuries to the eye or certain eye disorders can cause ocular hypertension. Certain medicines, such as steroids, can also elevate the intraocular pressure.

What are the risk factors for ocular hypertension?

Although ocular hypertension can develop at any age, the prevalence increases with age. People who are 40 years or older are more susceptible to develop ocular hypertension.

African-Americans and Hispanics are at high risk. According the Collaborative Initial Glaucoma Treatment Study (CIGTS), being non-White is a significant predictor of glaucoma.

With respect to sex, women are more likely to develop ocular hypertension than men. One of the reasons for women’s higher susceptibility is menopause-related changes in blood estrogen level, which is associated with an increased intraocular pressure. However, such physiological changes increase the risk of glaucoma more than they do the ocular hypertension.

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.