High eye pressure and Glaucoma

What is eye pressure?

Eye pressure is the measurement of force exerted by the aqueous humor fluid inside the front of the eye. The drainage angle of the eye allows aqueous humour to drain from the eye depending on fluid production, so that the eye pressure is maintained.

What causes high eye pressure?

High eye pressure occurs as a result of a build-up of aqueous humour fluid; this is either due to an imbalance in the rate at which the fluid is drained relative to the fluid produced, or due to a narrow or blocked drainage angle which restricts the drainage of the fluid.

What is considered normal eye pressure?

A ‘normal’ or average eye pressure ranges from 10mmHg to 24mmHg. If eye pressure is higher than this range it is called ocular hypertension or high eye pressure; the pressure can compress the optic nerve over time and damage it. A low eye pressure (below 5mmHg) is a very rare condition; it is called hypotony and can be caused by eye trauma or as a result of eye surgery. Hypotony can lead to eye problems including corneal swelling and decreased vision.

How to test eye pressure?

Tonometry is the procedure used to test the eye pressure to determine whether it is within the expected range or outside of its normal range. There are two main methods used for measuring eye pressure:

• Non-contact air puff tonometry. This method uses a small puff of air to determine eye pressure without touching the eye and is used by most high-street opticians. However, this method is not very accurate and can overestimate eye pressure
• Goldmann contact tonometry. This method does involve contact with the eye but numbing eye drops are used to avoid any discomfort. The measurement is adjusted to take into account the central corneal thickness – variations in corneal thickness result in falsely high or low readings with non-contact tonometry. This is the most accurate form of contact measurement and is done by trained opticians and all ophthalmologists

What are the symptoms of high eye pressure?

If the increase in eye pressure is gradual, there are no symptoms since the pressure builds very slowly.

On the other hand, the rapid rise in pressure that happens from a blocked drainage angle would result in symptoms that include pain in the eye, blurred vision, redness in the eye, and seeing halos around light.

How is high eye pressure treated?

High eye pressure is a major risk factor for glaucoma because the higher than average pressure can result in the optic nerve being damaged over time. There are several treatments for glaucoma depending on the type of glaucoma that is diagnosed – open angle or closed angle; both laser and surgical treatments are available. Learn more about the procedures here.