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Elevated intraocular pressure is called ocular hypertension, meaning that the pressure inside the eye is higher than normal. Eye pressure is measured in millimeters of mercury (mm Hg). Normal eye pressure ranges from 10-21 mm Hg. Ocular hypertension is an eye pressure greater than 21 mm Hg. One of the most common threats to vision is glaucoma, damage to the nerve that takes visual signals from the eye to the brain, is often caused by elevated intraocular pressure. The big problem is that most people with ocular hypertension do not experience any symptoms. That’s why regular eye examinations with an ophthalmologist are very important for the diagnosis.
Normal aqueous humor cycle
A specific layer of cells behind the iris, the colored part of the eye, produces humor aqueous as it’s primary role. Normally, the fluid passes through a hole in the centre of the iris called the pupil, to leave the eye through tiny drainage channels localized behind in the corner of the front of the eye and the iris. Then, this fluid normally returns to the blood stream.
Possible causes of ocular hypertension
Many people are not aware that the elevated intraocular pressure is a serious condition 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 aqueous humor. The channels that normally drain this fluid from inside the eye do not function properly causing the fluid to stay in the eye and thus increase the pressure.
Diagnosis of ocular hypertension
Although its definition has evolved through the years, ocular hypertension is commonly defined as the condition with the following criteria:
- An intraocular pressure higher than 21 mm Hg is measured in one or both eyes on 2 or more occasions.
- The optic nerve should appear normal.
- No signs of glaucoma are evident
- No signs of any ocular disease are present.