Optic Nerve Causes

CAUSES The main factor that leads to the damage of optic nerve is elevated pressure in the eye. The optic nerve is the main visual nerve of the eye. It transmits the images we see back to the brain for interpretation. The shape and tone of the eye is maintained by a pressure within the eye, which ranges between 8 mm and 22 mm of mercury. When this pressure is too low, the eye becomes softer, while an elevated pressure causes the eye to become harder. The optic nerve is the most susceptible part of the eye to high pressure because the delicate fibers in this nerve are easily damaged either by direct pressure on the nerve or decreased blood flow to the nerve.
The front of the eye is filled with a clear fluid called the aqueous humor, which provides
nourishment to the structures in the front of the eye. This fluid is produced constantly by the ciliary body, which surrounds the lens of the eye.
The aqueous humor then flows through the pupil and leaves the eye through tiny drainage channels called the trabecular meshwork. These channels are located at what is called the drainage angle of the eye. This angle is where the clear cornea, which covers the front of the eye, attaches to the base of the iris, which is the colored part of the eye. The cornea covers the iris and the pupil, which are in front of the lens. The pupil is the small, round, black-appearing opening in the center of the iris. Light passes through the pupil, on through the lens, and to the retina at the back of the eye. This diagram shows the drainage angle of the eye. The front part of the eye is in cross section to show the filtering, or drainage, angle. This angle is between the cornea and the iris, which join each other right where the drainage channels are located. The arrow shows the flow of the aqueous fluid from the ciliary body, through the pupil, and into the drainage channels. In most people, the drainage angles are wide open, but in some individuals, they can be narrow. For example, the usual angle is about 45 degrees, whereas a narrow angle is about 25 degrees or less.
After exiting through the trabecular meshwork in the drainage angle, the aqueous fluid then drains into tiny blood vessels into the main bloodstream. The aqueous humor should not be confused with tears, which are produced by the lacrimal glands under the upper eyelid outside of the eyeball itself. If the eye's trabecular meshwork becomes clogged or blocked, the intraocular pressure may become elevated. Also, if too much fluid is being produced within the eye, the intraocular pressure may become too high. In either event, since the eye is a closed system, if it cannot adequately remove the increased fluid, the pressure builds up and optic-nerve damage may result.