Understanding Glaucoma

Glaucoma is a disease in which the optic nerve is damaged, leading to progressive, irreversible loss of vision. It is one of the leading causes of blindness in the United States. Glaucoma is often, but not always, associated with increased pressure inside the eye. There are many different types of glaucoma, but they all result in permanent damage to the optic nerve. The optic nerve is made up of millions of small nerve fibers that connect the retina of your eye to the vision center in your brain. The transmission of electrical impulses along these nerve fibers creates an image in your brain to give you sight. In Glaucoma, damage occurs to the optic nerve in a manner that affects peripheral vision (side vision) first and center vision late in the disease process. Glaucoma is often called “the silent thief of sight” because people with the disease often have no symptoms until severe vision loss has occurred. If detected early and treated with eye drops, laser or surgery, severe vision loss can be prevented. Anyone with a family history of glaucoma should have a complete eye exam by an ophthalmologist.

Glaucoma Testing

Glaucoma typically causes a slow progressive loss of vision. There are no symptoms until significant vision loss has occurred therefore screening exams and early detection of disease are extremely important to prevent permanent vision loss. When screening for glaucoma your ophthalmologist will carefully examine your eyes to evaluate your optic nerve for excessive cupping. The cup of the optic nerve is an area of depression in the center of the nerve. Cup size can vary among individuals, but, as a general rule, cupping under 50% of the diameter of the nerve is considered to be normal. If the cup is estimated to be larger than 50% this can sometimes indicate glaucoma damage to the optic nerve. In addition, your ophthalmologist will order a special imaging test of the optic nerve which can measure the thickness of these nerve fibers as they enter the optic nerve. Areas of thinning on this test can indicate glaucoma damage. This test is called an OCT and will be performed regularly for screening and monitoring of glaucoma.

If you are a glaucoma suspect or you have glaucoma your ophthalmologist will also check a visual field test regularly to monitor for development of peripheral vision loss, which is a hallmark of this eye condition.

Tonometry is the term used for measuring eye pressure. This test will be performed at every visit. Tonometry can determine the eye pressure by measuring the amount of force required to indent the cornea. If the cornea is thicker than average the tonometry reading is more elevated than the actual pressure inside the eye. In contrast, if the cornea is thinner than average the eye pressure is lower than the actual pressure inside the eye. For this reason the thickness of the cornea is measured with a test called pachymetry.

The eye pressure is determined by a balance between the amount of fluid produced inside the and the amount of fluid leaving the eye. The drain of the eye, called the trabecular meshwork, is contained in the angle formed by the cornea and iris. The angle can be viewed by a technique called gonioscopy where a special mirrored lens is applied to the cornea. Gonioscopy can help to identify narrowing and other abnormalities of the drainage angle which can lead to glaucoma.

Glaucoma Treatment

When your risk of developing glaucoma is high or if you are diagnosed with glaucoma your ophthalmologist may recommend treatment. Treatment options vary but usually begin with eye drop medications to lower the eye pressure. Laser treatment may also be recommended to lower eye pressure or to prevent against abrupt closure of the drainage angle. In more advanced cases surgical options may be recommended.

Glaucoma Eye Drops
Glaucoma Laser
Glaucoma Surgery