Ocular hypertension is a condition in which the eye pressure is higher than usual. Increased eye pressure is also a sign of glaucoma, but ocular hypertension is notably different.
Ocular hypertension does not have any of the physiological changes or damage that come with glaucoma. Ocular hypertension may be monitored or treated similarly to glaucoma depending on the relative risk of conversion into glaucoma.
What is the Eye Pressure?
Eye pressure, or intraocular pressure (IOP), is the pressure exerted on the inside of the eye from the fluid in the front of the eyes.
The fluid, called aqueous fluid, is produced behind the iris and flows through the pupil into the space between the cornea and the iris.
The amount of fluid in the front of the eye is dependent on the rate that the aqueous is produced and the rate that it is drained.
If the aqueous is produced too rapidly or drains too slowly, the eye pressure will rise.
In most individuals, the eye pressure is within the normal range between 10 and 20 millimeters of Mercury.
Testing for Eye Pressure
Intraocular eye pressure can be tested in many ways in an eye examination. The most common ways to check eye pressure include applanation using a yellow dye, the air puff test (non-contact tonometry), and a handheld device called an iCare tonometer.
At every routine eye examination, the intraocular eye pressure will be measured and recorded.
This allows for screening for both ocular hypertension and glaucoma and provides a history of the previous eye pressure to compare against.
Having High Eye Pressure
Like high blood pressure, high eye pressure will not cause any symptoms that are noticed, and it can only be identified by having a screening at an eye exam.
If the eye pressure is elevated, the eye exam will also have other ways to determine whether the elevated pressure is due to ocular hypertension or glaucoma.
It is possible for eye pressure to fluctuate both throughout the day and between days so having only one high eye pressure reading may still be within the normal limits if the other readings are all within the typical range.
Difference Between Ocular Hypertension and Glaucoma
If the eye pressure is consistently higher than normal, then either ocular hypertension or glaucoma is causing the elevated pressure.
Ocular hypertension is elevated eye pressure without any associated change or damage from the high pressure.
Glaucoma is elevated eye pressure with some form of physical change or damage to the eye. This damage is identified in an eye examination by the eye doctor when evaluating the retina and the back of the eye.
To better distinguish between ocular hypertension and glaucoma, additional tests may be performed to assess the health of the retina and the function of the retinal cells.
Conversion from Ocular Hypertension to Glaucoma
If there is no current damage and the diagnosis is ocular hypertension, there is still a risk that there will be damage in the future and glaucoma will develop.
If there are risks for glaucoma besides ocular hypertension, then treatment may be initiated as a preventative measure even in cases of ocular hypertension.