The optic nerve is a structure containing about 1.2 million nerve fibers of the retinal ganglion cells of one retina, which connecting the eye ball and the brain, transmitting visual information from the retina of the eye to the visual system of the brain.
The optic nerve is the second of twelve pair of cranial nerves, called cranial nerve II, which begins from the retinal ganglion cell axons, and leaves the orbit via the optic canal to the optic chiasm, and terminates in the lateral geniculate nucleus from where visual information is sent to the occipital lobe of the brain via visual cortex. The optic nerve is about 50mm long (1mm in the globe, 24mm in the orbit, 9mm in the optic canal and 16mm in the cranial space), and the diameter of the optic nerve increase from 1.6mm to 4.5mm along from the eye to the brain.
The point where optic nerve leaves the eye is called the eye's blind spot, caused by the absence of photoreceptors in the area of retina.
When the optic nerve is injured, vision loss may occur. The type of vision loss depends on the part of the optic nerve that was damaged. Damage before the optic chiasm causes vision loss in the same side only. Damage in the optic chiasm causes vision loss in both eyes. Damage after the chiasm causes vision loss on one side and may also affect the other eye, for instance, causing eye diseases.
Ophthalmologists, especially an expert in the sub specialists, who are called neuro-ophthalmologists, are need for diagnosing and treating the diseases of the optic nerve.
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