The optic disc is the area where nerve fibers collected in the retina gather together and exit the eyeball as the optic nerve, which transmits visual information to the brain.

The optic disc does not contain photoreceptor cells (light‑sensing cells).
Therefore, images that fall on this area cannot be detected by the eye, and this region is known as the “blind spot.”
However, in normal vision the brain compensates using surrounding visual information, so people are usually not aware of this blind spot.

The optic disc is the exit where nerve fibers leave the eye and travel toward the brain, and the center of this area is slightly depressed.
This central depression is called the “optic disc cup.”
The optic disc is composed of many bundles of nerve fibers, but the central region contains relatively fewer fibers, which is why a natural depression exists there.

When diseases such as glaucoma damage the optic nerve, this depression may enlarge. As the condition progresses, parts of the visual field may gradually be lost.

However, some people naturally have a larger optic disc cup, so a large cup does not necessarily mean glaucoma.
What is most important is whether the depression is progressing over time, which is why regular ophthalmic examinations and follow‑up are essential.