What is Glaucoma?

Glaucoma is a disease that causes deterioration of the optic nerve. Vision loss from glaucoma is permanent but can usually be prevented with early detection and treatment. Because the symptoms of early glaucoma are so slight, the disease often goes unnoticed until significant, permanent vision loss has occurred.

Glaucoma is a disease caused by increased intraocular pressure (IOP) resulting either from a malformation or malfunction of the eye’s drainage structures. Left untreated, an elevated IOP causes irreversible damage to the optic nerve and retinal fibers resulting in a progressive, permanent loss of vision. When glaucoma damages your optic nerve, transmission of visual information from the eye to the brain is limited which causes visual impairment. Glaucoma typically causes you to begin to lose patches of vision, usually side (peripheral) vision initially. Over time, glaucoma may also damage straight ahead (central) vision. You may not notice a loss of peripheral vision until you have lost a great deal of your sight.

A clear liquid called aqueous humor circulates inside the front portion of the eye. To maintain a healthy level of pressure within the eye, a small amount of this fluid is produced constantly while an equal amount flows out of the eye through a microscopic drainage system. This liquid is not part of the tears on the outer surface of the eye.

Glaucoma causes damage to the nerve fibers of retinal ganglion cells and is manifest clinically by alterations in the appearance of the optic disc. There is a rather typical sequence of change that occurs to the optic disc in uncontrolled glaucoma.

Optic Nerve Head Cupping a. – d., left to right; C/D = Cup-to-Disc Ratio)

a. Normal optic nerve head with small central physiologic cup, C/D ratio ~ 0.2
b. Concentric enlargement of the central cup, C/D ratio ~ 0.5
c. Irregular enlargement of the cup, especially inferiorly due to loss of inferior neural rim tissue, C/D ratio ~ 0.7
d. Marked glaucoma cupping with high degree of central atrophy and loss of inferior rim, C/D ratio ~ 0.9