Ocular hypertension is increased pressure inside the eye.
Ocular hypertension increases a person's risk of developing glaucoma. Around 10% of people with untreated ocular hypertension go on to develop glaucoma.
Eye pressure, also called intraocular pressure or IOP, is measured in millimetres of mercury (mmHg) using a procedure called tonometry.
Pachymetry, or corneal thickness, may be checked by an ultrasound probe to determine the accuracy of the intraocular pressure readings. A thinner cornea can give false low pressure readings, whereas a thick cornea can give false high pressure readings.
If high pressure is detected, further vision tests, monitoring or specialist referrals may be recommended.
Normal eye pressure ranges from 10 to 21 mmHg. Ocular hypertension is an eye pressure of greater than 21 mmHg.
The condition affects around 3-5% of people over 40.
Ocular hypertension causes
High pressure inside the eye is caused by an imbalance in the production and drainage of fluid in the eye (aqueous humour). The channels that normally drain the fluid from inside the eye do not function properly. More fluid is continually being produced but cannot be drained because of the improperly functioning drainage channels. This results in an increased amount of fluid inside the eye, thus raising the pressure.
Another way to think of high pressure inside the eye is to imagine a water balloon. The more water that is put into the balloon, the higher the pressure inside the balloon. The same situation exists with too much fluid inside the eye - the more fluid, the higher the pressure. Also, just like a water balloon can burst if too much water is put into it, the optic nerve in the eye can be damaged by too high pressure.
Ocular hypertension symptoms
Most people with ocular hypertension do not experience any symptoms. For this reason regular eye examinations with an ophthalmologist or other eye care professional are very important to rule out any damage to the optic nerve from the high pressure.
Treatment for ocular hypertension
If an eye specialist believes the eye pressure is too high, medication, usually in the form of eye drops, are prescribed to help lower intraocular pressure.
Laser and surgical therapy are not generally used to treat ocular hypertension because the risks associated with these therapies are higher than the actual risk of developing glaucomatous damage from ocular hypertension. However, if you cannot tolerate your eye medications, laser surgery could be an option, and you should discuss this therapy with the specialist.
Next steps - follow-up
Depending on the level of intraocular pressure control, people with ocular hypertension may need to be seen from every two months to yearly, even sooner if the pressures are not being adequately controlled.
Glaucoma should still be a concern in people who have elevated intraocular pressure with normal-looking optic nerves and normal visual field testing results or in people who have normal intraocular pressure with suspicious-looking optic nerves and visual field testing results. These people should be observed closely because they are at an increased risk of glaucoma.
Ocular hypertension cannot be prevented, but through regular eye examinations with an eye specialist, its progression to glaucoma can be prevented.
The prognosis is very good for people with ocular hypertension.
- With careful follow-up care and compliance with medical treatment, most people with ocular hypertension do not progress to primary open-angle glaucoma, and they retain good vision throughout their lifetime.
- With poor control of elevated intraocular pressure, continuing changes to the optic nerve and visual field that could lead to glaucoma might occur.