Ocular hypertension overview
The term ocular hypertension usually refers to any situation in which the pressure inside the eye, called intraocular pressure (IOP), is higher than normal. Eye pressure is measured in millimetres of mercury (mmHg). Normal eye pressure ranges from 10 to 21 mmHg. Ocular hypertension is an eye pressure of greater than 21 mmHg.
Although its definition has evolved through the years, ocular hypertension is commonly defined as a condition with the following criteria:
- An intraocular pressure of greater than 21 mmHg is measured in one or both eyes on two or more occasions. Pressure inside the eye is measured using an instrument called a tonometer.
- The optic nerve appears normal.
- No signs of glaucoma are evident on visual field testing, which is a test to assess your peripheral (or side) vision.
- No signs of any ocular disease are present. Some eye diseases can increase the pressure inside the eye.
Ocular hypertension should not be considered a disease by itself. The term ocular hypertension is used to describe the condition of individuals who should be observed more closely than the general population for the onset of glaucoma. For this reason another term that may be used to refer to an increase in intraocular pressure is ‘glaucoma suspect’. A glaucoma suspect is a person whom an ophthalmologist (a medical doctor who specialises in eye care and surgery) is concerned may have or may develop glaucoma because of the elevated pressure inside the eyes.
As mentioned above, increased intraocular pressure can result from other eye conditions, but within this article ocular hypertension primarily refers to increased intraocular pressure without any optic nerve damage or vision loss. Glaucoma occurs when increased intraocular pressure, optic nerve damage and vision loss are present.
In the UK glaucoma affects about 2% of adults over 40. Worldwide, over 12% of blindness is caused by glaucoma. These statistics alone emphasise the need to identify and closely monitor people who are at risk of developing glaucoma, particularly those with ocular hypertension.
Some studies have found that the average intraocular pressure in people of African or African-Caribbean descent is higher than in white people, while other studies have found no difference.
Although some studies have reported a significantly higher average intraocular pressure in women than in men, other studies have not shown any difference between men and women.
- Some studies suggest that women could be at a higher risk for ocular hypertension, especially after menopause.
- Studies also show that men with ocular hypertension may be at a higher risk for glaucomatous damage.
Intraocular pressure slowly rises with increasing age, just as glaucoma becomes more prevalent as you get older.
- Being older than 40 is considered to be a risk factor for the development of both ocular hypertension and primary open-angle glaucoma.
- Elevated pressure in a young person is a cause for concern. A young person has a longer time to be exposed to high pressures over a lifetime and a greater likelihood of optic nerve damage.