Glaucoma

What causes glaucoma?

Glaucoma is caused by pressure build-up inside the eye. This increased pressure is due to a backup of fluid.

Normally,  this fluid, called the aqueous humor, fills the area just behind the iris (the colored part of the eye). The fluid flows around the eye to nourish the cornea (the clear outer layer at the front) and lens (the curved part of the eye behind the pupil). After bathing the eye, this fluid drains through the trabecular meshwork, the spongy tissue in the eye’s corner where the cornea and iris meet.

In glaucoma, this drainage system breaks down, slowing or blocking the outflow of fluid. The fluid backs up in the eye, like water in a clogged sink, and the internal pressure rises. This, in turn, puts stress on the optic nerve. If the pressure continues unabated, nerve fibers that carry optical messages to the brain die off, and vision begins to fade.

The following factors increase the risk of glaucoma:

• A family history of glaucoma
• Age (60 and older, or age 40 and older for African Americans)
• Increased eye pressure
• Thin cornea
• Severe nearsightedness
• Eye surgery or injury
• High blood pressure or cardiovascular disease
• Diabetes
• Use of corticosteroid medicines

What are the symptoms of glaucoma?

Glaucoma is regarded as a silent disease. That’s because, in most forms, no signs or symptoms appear until the optic nerve becomes damaged from rising eye pressure and vision begins to fade.

In its later stages, glaucoma symptoms include blind spots in the peripheral (side) vision and tunnel vision (vision that has narrowed so you see only what is directly in front of you, like looking through a railroad tunnel.)
 
Closed-angle glaucoma is the most severe form and can cause permanent optic nerve damage and even blindness in days or even hours. The onset of symptoms is usually rapid and severe. Seek immediate medical attention if you experience blurred vision, eye pain, light sensitivity, rainbow halos around lights, headaches, nausea, and vomiting.

What are the different types of glaucoma?

There are three common forms of glaucoma: open-angle, normal tension, and closed-angle.
 
Open-angle glaucoma. This is the most common form of the disease, accounting for more than 90% of all cases. It occurs when the passage through which fluid drains from the anterior chamber of the eye remains open, yet the aqueous humor drains too slowly. This leads to fluid backup and a gradual rise in pressure. Eventually excess pressure damages the optic nerve and causes vision loss.

Closed-angle glaucoma. Also known as narrow-angle, this form of glaucoma causes eye pressure to rapidly rise. This occurs when the angle between the iris and cornea narrows so much that the iris suddenly blocks fluid from flowing out, resulting in a quick rise in eye pressure. Closed-angle glaucoma is a medical emergency that must be treated immediately to prevent vision loss.

Normal-tension glaucoma. Approximately 30% of people with open-angle glaucoma have eye pressures that fall in the normal range, but the optic nerve still sustains damage. Symptoms don’t usually occur until late in the disease, when blind spots may appear in the peripheral (side) vision. Your doctor will probably check for this problem if your pressure is at the high end of the normal range or if you have suspicious-looking optic nerves or other risk factors, such as

• abnormal blood flow in the eye
• an autoimmune disease
• low blood pressure
• a disorder that affects blood vessels, such as migraines or Raynaud’s phenomenon
• a family history of glaucoma

What are treatments for glaucoma?

Although there is currently no cure for glaucoma, prompt treatment can help slow or stop the progression of vision loss. Depending on many factors, including your age and the type and severity of your glaucoma, treatment may include medicated eye drops and/or surgery.

Eye drops. Medicated eye drops work to lower eye pressure by either helping fluid drain more easily from the eye or reducing the amount of fluid the eye makes.

Laser surgery. Laser surgery creates an opening for the fluid to drain from the eye. Laser trabeculoplasty is used for open-angle glaucoma and stimulates the fluid channels in the eye to help fluid drain more effectively. Laser peripheral iridotomy is used for closed-angle glaucoma; a laser creates a hole no bigger than the head of a pin in the iris, which allows fluid to drain internally through the trabecular meshwork of the eye.

Conventional surgery. If medicine and laser surgery don’t work or aren’t an option, doctors can surgically create a new channel for fluid to drain. Examples include trabeculectomy (the most common surgery) and tube shunt implantation. Micro-invasive glaucoma surgery (MIGS) increases fluid drainage using implantable microscopic-sized stents and shunts.