What is the intraocular portion of the optic nerve called?
The optic nerve head (i.e. intraocular part) measures about 1 mm in length. The intraorbital part is approximately 25 mm in length. The intracanalicular part is most variable, ranging between 4 – 10 mm in length. The Intracranial part accounts for about 10 mm of the total length of the nerve.
What is Prelaminar region of optic disc?
The most anterior zone of the optic nerve is the superficial nerve fiber layer region. Immediately posterior to this is the prelaminar region, which lies adjacent to the peripapillary choroid. More posteriorly, the laminar region is continuous with the sclera and is composed of lamina cribrosa.
What are the parts of the optic nerve?
The optic nerve has four major portions: intraocular, intraorbital, intracanalicular, and intracranial. Posterior to the lamina cribrosa, optic nerve axons are myelinated by oligodendrocytes similar to those in white matter tracts in the brain and spinal cord.
What connective tissue surrounds the optic nerve?
The optic nerve intraorbital segment extends from the eyeball to the orbit and becomes enveloped in meninges consisting of three layers: dura mater (outer), arachnoid (center), and pia mater (inner). The intraorbital optic nerve in all three species is surrounded by connective tissue, fat, and the rectus muscles.
What is the function of Abducens nerve?
The abducens nerve functions to innervate the ipsilateral lateral rectus muscle and partially innervate the contralateral medial rectus muscle (at the level of the nucleus – via the medial longitudinal fasciculus).
What is the function of the fovea?
Structure and Function The fovea centralis is located in the center of the macula lutea, a small, flat spot located exactly in the center of the posterior portion of the retina. As the fovea is responsible for high-acuity vision it is densely saturated with cone photoreceptors.
What does Peripapillary mean?
Medical Definition of peripapillary : situated around the optic papilla.
What is the colored portion of the eye?
Iris
Iris. The colored part of the eye. The iris is partly responsible for regulating the amount of light permitted to enter the eye. Lens (also called crystalline lens).
What is the name of the outermost layer of the anterior eye?
The sclera is the tough outer layer of the eyeball (the white of the eye). The slight bulge in the sclera at the front of the eye is a clear, thin, dome-shaped tissue called the cornea.
What fluid surrounds the optic disc?
The front part of the eye is filled with a clear fluid (called aqueous humor) made by the ciliary body. The fluid flows out through the pupil. It then reaches the eye’s drainage system, including the trabecular meshwork and a network of canals.
What is the structure of the optic nerve?
The optic nerve (ON) is constituted by the axons of the retinal ganglion cells (RGCs). These axons are distributed in an organized pattern from the soma of the RGC to the lateral geniculated nucleus (where most of the neurons synapse). The key points of the ON are the optic nerve head and chiasm.
What is the most common cause of optic nerve entrapment?
The condition is caused by infarction of the laminar or retrolaminar portion of the optic nerve head supplied by the short posterior ciliary arteries (SPCAs). The un … Non-arteritic anterior ischaemic optic neuropathy (NAION) is the most common acute optic neuropathy in people aged 50 years and older.
What is non-arteritic anterior ischaemic optic neuropathy?
Non-arteritic anterior ischaemic optic neuropathy (NAION) is the most common acute optic neuropathy in people aged 50 years and older. The condition is caused by infarction of the laminar or retrolaminar portion of the optic nerve head supplied by the short posterior ciliary arteries (SPCAs).