The optic cup, or ophthalmic cup, is a two-walled depression that can be found in the center of the eye's optic disc. This area is named for its location and its cup-like shape. The optic cup is one of the components of the visual system, and overall, it has an important role in ophthalmology, a branch of medicine that involves the study of the eye.
The cup-like region of the eye is formed during the early stages of development, thus making it a part of the embryology specialization of medicine. It is when the bulb of the optic vesicles—protruding parts of the developing anterior portion or frontal area of the brain—acquire a certain thickness and begin to sink backward, that the optic cup is created. The area resulting from this process, called invagination, then uses the two layers of cells it has derived to create the light-sensitive tissue that lines the inner surface of the eye called the retina.
The cellular strata that constitute the optic cup cover the entire cup margin. They also cover the lens at its front and stretch toward the pupil's aperture. Each layer has a specific role in the formation of the retina. The outer layer is responsible for creating the membrane's pigmentation. The inner layer, on the other hand, takes care of the retina's sensory elements, which include supporting nerves and fibers.
The optic disc—the center of which is the optic cup—is also known as the optic nerve head. This is because it is where a mass of nerve fibers formed from retinal ganglion cells leave the eye to create the optic nerve. This part of the eye is particularly important because it provides visual information from the retina to the brain. Described as a circular region, the optic disc can be found at the rear of the eye's interior, where the retina and optic nerve connect. This connection area is known as the eye's "blind spot."
The optic cup is used to diagnose glaucoma. This is an eye disorder that concerns damage to the optic nerve. Left untreated, the optic nerve could become permanently damaged, and the patient could go totally blind. Doctors or medical professionals specializing in eye care—ophthalmologists, optometrists and orthoptists—can diagnose this condition by relying on a cup-to-disc ratio. This means they have to figure out the optic cup's size in relation to the total diameter of the optic disc.