What Are the Causes of Raised Intraocular Pressure?

Raised intraocular pressure can lead to vision problems, including blindness, and the process often is slow and painless. In rare cases, glaucoma suddenly attacks, accompanied by pain and headaches. But for the most part, high intraocular pressure, or ocular hypertension, is a silent condition that can gradually damage the optic nerve and rob you of your eyesight.

How It Happens

• Fluid constantly flows into and drains out of the eye, keeping its parts moist and functioning properly. Intraocular pressure builds when the fluid cannot exit and accumulates between the lens and fibrous tissue behind the lens. This pressure eventually causes vision problems.

Open-angle Glaucoma

• In some cases intraocular pressure can build between the cornea and the iris. To facilitate fluid drainage, the cornea and the iris have what's known as a drainage angle between them. A drainage angle is the equivalent of a series of tubes that allow fluid to flow out of the eye. Within these tubes is a series of drainage channels known as the trabecular meshwork. If the trabecular meshwork becomes obstructed, it can cause fluid to back up into the eye, leading to raised intraocular pressure. This condition is known as open-angle glaucoma. It is unknown why the trabecular meshwork develops a tendency to become blocked.

Closed-angle Glaucoma

• Closed-angle glaucoma develops when the iris bulges and blocks the drainage angle that operates between the iris and the cornea. Fluid begins to build and the intraocular pressure increases on the optic nerve. Closed-angle glaucoma can happen gradually or rapidly.
  With open-angle glaucoma the fluid slowly drains from the eye and builds up due to the pace of drainage. Eventually this causes increased intraocular pressure. Closed-angle glaucoma is usually a complete blockage of the trabecular meshwork, and that is why closed-angle glaucoma sometimes strikes relatively quickly.

Causes

• In some cases, anything that irritates the iris and causes it to swell can lead to an increase in intraocular pressure. Some eye drops irritate the iris, and the onset of diabetes or cataracts can cause inflammation in the iris.
  Extended use of cortisone or steroids also can cause inflammation of the iris that leads to raised intraocular pressure.
  An eye injury also could cause a blockage that raises intraocular pressure on the optic nerve. The injury could be recent or could have happened many years ago.

Additional Factors

• If the trabecular meshwork is not properly developed from birth, it will not allow the proper passage of fluids, eventually resulting in raised intraocular pressure.