Optic Nerve Pathway Anatomy

The optic disc or nerve head is the point where the axons from the retinal ganglion cells leave the eye. The axons of the retinal ganglion cells form the optic nerve.

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In the chiasm the nerve fibres from the nasal retina cross the midline and enter the optic tract of the opposite side.

Optic nerve pathway anatomy. Last Updated on Mon 01 Feb 2021 Brain Anatomy. After its formation the nerve leaves the bony orbit via the optic canal a passageway through the sphenoid bone. The optic stalk has a ventral groove the choroid fissure which contains hyaloid vessels.

The visual association cortex. The posterior visual pathway refers to structures after this point. The optic nerve also known as cranial nerve II or simply as CN II is a paired cranial nerve that transmits visual information from the retina to the brainIn humans the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells.

Retinic photoreceptors cones and rods relay the signal for further processing to other. Their axons pass through the optic nerve the optic chiasm form the optic tract and reach the lateral geniculate body of the thalamus. From the chiasm the same axons continue on as the optic tract.

The visual pathway extends from the globes anteriorly to the occipital cortex posteriorly. OPTIC NERVE Comprises axons of ganglion cells 47-50 mm length Extends from optic disc to chiasma Contains the afferent fibres of light reflex Has 4 parts. A wide variety of disease processes may produce visual dysfunction.

Intraocular part Passes through sclera choroid and appears in eye as optic disc Intraocular portion is of 15mm which expands to 3mm just behind eye because of myelin sheath ONH has 4 portions. The optic nerve is formed by the convergence of axons from the retinal ganglion cells. These axons travel to and synapse in the lateral.

The second cranial nerve is the optic nerve which is responsible for relaying sight back from the retina to the visual cortex in the occipital lobe. 1intraocular 1mm 2intraorbital 30mm 3intra canalicular 6-9mm 4intracranial 10mm. The optic nerve is the second cranial nerve which along with the olfactory nerve CN I is really an extension of the central nervous system.

Pathology of the visual pathways posterior to the chiasm is beyond the scope of this article and is discussed only briefly. The axons coming from the nasal hemiretina are crossed in. Optic Nerve Visual Pathway and Orbit I Optic Nerve and Visual Pathway.

Precise knowledge of the neuroanatomy of the visual system including the perception of visual stimuli in the retina the transmission of visual information to other areas of the central nervous system and the processing of visual information are most important for diagnostics of diseases which are affecting this system. The anterior visual pathway refers to structures involved in vision before the lateral geniculate nucleus. The optic nerve CN II Approximately one million myelinated axons arising from the ganglion cells of the retina come together at the optic disc to form the optic nerves CN II.

Pathway of the Optic Nerve After becoming the optic nerve the fibers from the ganglion cells travel to the lateral geniculate nucleus. This article focuses on pathologic processes affecting the optic nerve optic nervesheath complex and chiasm. Diagram highlighting the anatomical relationship of the sphenoid sinuses pituitary gland and optic chiasm.

Known to the Greek fathers of anatomy as nervus optikus the optic nerve has the responsibility of transmitting special afferent impulses of light to the brain. Optic Nerve Parts of optic nerve Intraocular 1 mm Intraorbital 30 mm Intracanalicular 6- 9mm Intracranial 10 mm 5. The optic nerve is mainly made up of the axons nerve fibers of the retinal ganglion cells from the retina.

It extends from the optic disc to the optic chiasma and continues as the optic. Clinical signs and symptoms Decrease in visual acuity and visual field defects are the cardinal symptoms of optic nerve lesions. The identity of cranial nerve II CN II also known as the optic nerve predates Galenic anatomy.

Arising from the posterior pole of each eye each optic nerve is about 35 mm and 55 mm in length and can be subdivided as follows. These cells in turn receive impulses from the photoreceptors of the eye the rods and cones. It is also involved in several reflex arcs related to the ocular system.

Because the optic nerve is a fiber tract of the brain covered by meninges it can be affected by many of the same pathologic processes that occur in the brain and meninges. The two optic nerves meet at the optic chiasm where the nerve fibers originating in the nasal retina of each eye decussate to join the temporal fibers of the fellow eye. The lateral geniculate body.

These are divided into anterior and posterior pathways. The optic stalk is a structure that connects the optic cup to the brain and it is readily distinguished at 4 weeks of gestation Rizzo 2005 Watanabe et al 2008. The retina and the optic nerve constitute the beginning of the visual pathway.

The optic nerve is formed from the remnants of the optic stalk as shown in Figure 192 Mann 1964 Ozanics and Jakobiec 1982. Similarly to the olfactory system the optic nerve is not a peripheral nerve as it is mostly an evagination of the telencephalon. Thirdly the oculomotor nerve which is essential for the movements of the eyeball.

The visual pathway is made up in addition to the retina and optic nerves ON of the optic chiasma optic tracts lateral geniculate nucleus LGN optic radiations and visual cortex. Unlike other nerves of the body that are myelinated by Schwann cells the fibers of the optic nerve are myelinated by oligodendrocytes. The fibers terminate in a small swelling under the pulvinar of the thalamus called the lateral geniculate body.

Large pituitary tumours can cause chiasmal compression which results in bi-temporal visual field loss. It is a unique structure that functions as the bridge between the retinal layer of the eyes and the visual cortex of the brain. It is not surrounded by Schwann cells with the first sensory bipolar cell body located peripherally in the retina.

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