What is the optical disc?

The optical disc is a vertically oval location at the back of the eye about three to four millimeters (0.14 to 0.18 inch) nasal in the center. It consists of the nerve fibers of the nerve cells, called ganglion cells, which reside in the light-sensitive layer of the back of the eye, called the retina. The 1,0-1,200,000 nerve fibers or axons of ganglion cells leave the eye at the level of the disc and form the optic nerve, which carries visual information to the brain. A physiological blind spot in the visual field of each eye results from the absence of light-sensitive cells, sticks and cones, to the optical disc. An examination of the optic disc through the pupil provides valuable diagnostic information on various ocular and neurological diseases.

On average, optical disk measurements are approximately 1.92 millimeters (0.09 inches) vertical by 1.76 millimeters (0.08 inches) horizontally. The optical cut is a small central depression in the disc, which generally extends about 33 percent of the disc area. Normally, the disc is pinkish yellowish orange with well-defined margins. The rim around the cup is slightly thicker at the lower pole, with the thinner part of the temporally located boundary. A standard ophthalmologic examination includes the notation of disc color, cup size, margin definition, associated bleeding or swelling, and rim abnormalities.

Glaucoma is a degenerative disease of the optic nerve usually associated with sustained elevation of intraocular pressure. A characteristic feature of glaucoma is the gradual expansion of the optical cut with respect to the size of the optic disc. Disc notching of the disc crown, as well as bleeding at the edge of the disc, may also occur. Progressive excavation of the optic disc is a sign of the pursuit of the retina nerve layer fiber slimming. Clinical studies show that lowering eye pressure by 20 to 30 percent effectively stops damage to the optic nerve in most cases.

A pale disc is indicative of poor blood flow or atrophy. Optic atrophy is the hallmark of ganglion cell damage. Degrees of severe damage are characterized by a chalky white disc color with Stark borders, unusually pronounced. Light degrees of atrophy can be recognized by comparing the disc color with the other eye. Optic atrophy occurs four to six weeks after cellular damage due to reduced blood flow or inflammation.

Optical disk swelling or edema occur due to nutrient deficiency flow through the axons. This can result from increased head pressure, reduced blood flow, inflammation, or mechanical compression. Optics features nerve edema include blurred margins of discs, bleeding around the disc, elevation of the head of the nerve, and a reddish color of the disc. Swelling of the disc may be a sign of a brain tumor, an orbital tumor, inflammation of the active optic nerve, or a mini stroke to the nerve.

Discus optic drusen are calcified nodules buried with the head of the optic nerve. Drusen cause an elevation of the head of the optic nerve with a festooned appearance. They are bilateral in 75 percent to 86 percent of cases. Although drusen usually produce no symptoms, temporary visual fluctuations and minor visual field defects are sometimes reported.

• The optical disc is located at the back of the eye.
• The optical disk of the eye is made up of nerve fibers and nerve cells.
• Glaucoma causes a progressive expansion of the optical cup in relation to the size of the optical disc.
• Glaucoma is a degenerative disease of the optic nerve that is usually associated with a steady rise in ocular pressure.