Causes of Glaucoma

Glaucoma causes include elevated eye pressure (called intraocular pressure or IOP) due to the eye’s inability to drain fluid efficiently. A clear fluid called aqueous humor circulates inside the front portion of our eyes. To maintain a constant healthy eye pressure, the eye continually produces a small amount of aqueous humor while an equal amount of this fluid flows out of the eye. The fluid flows out through a very tiny drain called the trabecular meshwork, a complex network of cells and tissue in an area called the drainage angle.

If the drainage angle is blocked, excess fluid cannot flow out of the eye, causing the fluid pressure to increase.

If you have glaucoma, the aqueous humor does not flow through the trabecular meshwork properly. If the drainage angle is become less efficient at draining fluid, as in the common open-angle glaucoma, excess fluid cannot flow out of the eye properly, causing the intraocular pressure (IOP) to increase. Over time, raised IOP causes damage to the nerve fibers. If the drainage angle becomes completely blocked, eye pressure rises quickly, resulting in a narrow-angle glaucoma or angle-closure glaucomaattack, with severe eye and brow pain, nausea and vomiting. This kind of glaucoma attack is a medical emergency and must be treated immediately.

Damage to the optic nerve can occur at different eye pressures among different patients. Your ophthalmologist (Eye M.D.) establishes a target eye pressure for you that he or she predicts will protect your optic nerve from further damage. Different patients have different target pressures.

Some people have a type of glaucoma called normal tension, or low tension glaucoma. Their eye pressure is consistently below 21 mm Hg, but optic nerve damage and visual field loss still occur.

Congenital glaucoma is a rare type of glaucoma that develops in infants and young children. It can be hereditary, and it happens when the eye’s drainage system doesn’t develop fully or correctly before birth.

Glaucoma can often be caused by another eye condition or disease. This is known as secondary glaucoma. For example, someone who has a tumor or people undergoing long-term steroid therapy may develop secondary glaucoma. Other causes of secondary glaucoma include:

  • Eye injury;
  • Inflammation of the eye;
  • Abnormal blood vessel formation from diabetes or retinal blood vessel blockage;
  • Use of steroid-containing medications (pills, eyedrops, sprays); or
  • Pigment dispersion, where tiny fragments or granules from the iris (the colored part of the eye) can circulate in the aqueous humor (the fluid within the front portion of the eye) and block the trabecular meshwork, the tiny drain for the eye’s aqueous humor.