Optic nerve and opthalmic artery
-
Upload
rehan-asad -
Category
Documents
-
view
223 -
download
0
Transcript of Optic nerve and opthalmic artery
-
8/7/2019 Optic nerve and opthalmic artery
1/45
Optic nerve and opthalmic artery
-
8/7/2019 Optic nerve and opthalmic artery
2/45
-
8/7/2019 Optic nerve and opthalmic artery
3/45
Cranial Nerve II: Optic
y Arises from the retina
of the eye
y Function: sensory -
solely for visiony Exits through optic
canal
-
8/7/2019 Optic nerve and opthalmic artery
4/45
-
8/7/2019 Optic nerve and opthalmic artery
5/45
y The optic nerve is the second cranial nerve
y It arises from the optic chiasma on the floor of the diencephalon
y Enters the orbit through the optic canal, accompanied by the
ophthalmic artery
y It changes its shape from being flattened at the chiasma to
rounded as it passes through the optic canal
y Nerve is extension of brain covered by meninges
y Length: 4 cm ; 2.5 mm intraorbital and 5 mm intracanalicular
and 10 mm intracranial
yIn the orbit it passes forwards, laterally and downwards, andpierces the sclera 3mm medial to the posterior pole
y It has a somewhat tortuous course within the orbit to allow for
movements of the eyeball
-
8/7/2019 Optic nerve and opthalmic artery
6/45
-
8/7/2019 Optic nerve and opthalmic artery
7/45
y Special somatic afferents (SSA) are found only in supraspinal locationsand are represented by the laterally-lying vestibular and auditory nucleiin the medulla and pons.
y They develop from branchial arch structures.
Cranial nerves I and II serve vision (SSA) and olfaction (SVA)
y However, these are not true nerves.
y Rather they develop as evaginations of the telencephalon (olfactorynerve) and the diencephalon (optic nerve)
y I I(optic) SSA:
y Originates in ganglion cells of retina
y Lateral geniculate nucleus and superior colliculus
-
8/7/2019 Optic nerve and opthalmic artery
8/45
y The optic nerve or nerve of sight, consists mainly of fibers
derived from about 1.2 million ganglionic cells of the retina
y These axons terminate around the cells in the lateral geniculate
body, pulvinar, and superior colliculus which constitute the loweror primary visual centers
y From the cells of the lateral geniculate body and the pulvinar
fibers pass to the cortical visual center, situated in the cuneus and
in the neighborhood of the calcarine fissure
y There are also a few fine fibers, afferent fibers, extending from
the retina to the brain, that are supposed to be concerned in
pupillary reflexes
-
8/7/2019 Optic nerve and opthalmic artery
9/45
-
8/7/2019 Optic nerve and opthalmic artery
10/45
-
8/7/2019 Optic nerve and opthalmic artery
11/45
Relationsy The optic nerve has important relationships with other orbital structure
y As it leaves the optic canal, it lies superomedial to the ophthalmic artery,and is separated from lateral rectus by the oculomotor, nasociliary and
abducens nerves, and sometimes by the ophthalmic veins
y The optic nerve is closely related to the origins of the four recti muscles,
whereas more anteriorly, where the muscles diverge, it is separated fromthem by a substantial amount of orbital fat
y Just beyond the optic canal, the ophthalmic artery and the nasociliary
nerve cross the optic nerve to reach the medial wall of the orbit
-
8/7/2019 Optic nerve and opthalmic artery
12/45
-
8/7/2019 Optic nerve and opthalmic artery
13/45
-
8/7/2019 Optic nerve and opthalmic artery
14/45
-
8/7/2019 Optic nerve and opthalmic artery
15/45
-
8/7/2019 Optic nerve and opthalmic artery
16/45
y The central artery of the retina enters the substance of the optic
nerve inferomedially about 1.25 cm behind eye ball
y Near the back of the eye, it becomes surrounded by long andshort ciliary nerves and vessels
-
8/7/2019 Optic nerve and opthalmic artery
17/45
y Medial palpebral branch: supply eyelids
y Dorsal nasal branch supply upper part of nose
y Optic nerve has no neurilemmal sheathy It has no power of regeneration
y It is tract
y Optic nerve atrophy is damage to the optic nerve
y The optic nerve can also be damaged by shock, various toxic
substances, radiation, and trauma
-
8/7/2019 Optic nerve and opthalmic artery
18/45
Opthalmic artery
y The main vessel supplying orbital structures is the
ophthalmic artery
y Its terminal branches anastomose on the face and scalp with
those of the facial, maxillary and superficial temporalarteries,
y Establishing connections between the external and internal
carotid arteries
y
In addition to the ophthalmic artery, the infraorbital branchof the maxillary artery, and possibly the recurrent meningeal
artery, supply orbital structures
-
8/7/2019 Optic nerve and opthalmic artery
19/45
y The ophthalmic artery leaves the internal carotid artery as it
quits the cavernous sinus medial to the anterior clinoid process
y It enters the orbit by the optic canal, inferolateral to the opticnerve
y It crosses between the optic nerve and superior rectus to reach
the medial wall of the orbit, running between superior oblique
and medial rectus.
y At the medial end of the upper eyelid, it divides into
supratrochlear and dorsal nasal branches
-
8/7/2019 Optic nerve and opthalmic artery
20/45
y As it crosses the optic nerve with the nasociliary nerve, it is
separated from the frontal nerve by superior rectus and levator
palpebrae superiorisy In c.15% of subjects the ophthalmic artery crosses below the
optic nerve
y It has the following branches:
y Central artery of the retina, lacrimal artery, muscular branches,ciliary arteries, supraorbital artery, posterior ethmoidal artery,
anterior ethmoidal artery, meningeal branch, medial palpebral
arteries, supratrochlear artery, dorsal nasal artery
-
8/7/2019 Optic nerve and opthalmic artery
21/45
-
8/7/2019 Optic nerve and opthalmic artery
22/45
-
8/7/2019 Optic nerve and opthalmic artery
23/45
y Central artery of the retina :The small central artery of the
retina is the first branch
y It begins below the optic nerve and for a short distance
y it lies in the dural sheath of the nerve
y It enters the inferomedial surface of the nerve c.1.25 cm behind
the eye
y Runs to the retina along its a muscular branches
y The central retinal artery supplies all the nerve fibers that form
the optic nerve
-
8/7/2019 Optic nerve and opthalmic artery
24/45
-
8/7/2019 Optic nerve and opthalmic artery
25/45
y There are three groups of ciliary arteries: long and short posterior, and
anterior
y Long posterior ciliary arteries, usually two, pierce the sclera near the optic
nerve, pass anteriorly along the horizontal meridian and join the greaterarterial circle in the iris
y About seven short posterior ciliary arteries pass close to the optic nerve to
reach the eyeball where they divide into 15-20 branches
y T
hey pierce the sclera around the optic nerve to supply the choroid, andanastomose with twigs of the central retinal artery at the optic disc
y Anterior ciliary arteries :They reach the eyeball on the tendons of the recti,
form a circumcorneal subconjunctival vascular zone, and pierce the sclera
near the sclerocorneal junction to end in the greater arterial circle of the iris
-
8/7/2019 Optic nerve and opthalmic artery
26/45
-
8/7/2019 Optic nerve and opthalmic artery
27/45
-
8/7/2019 Optic nerve and opthalmic artery
28/45
-
8/7/2019 Optic nerve and opthalmic artery
29/45
-
8/7/2019 Optic nerve and opthalmic artery
30/45
y The lacrimal artery is a large branch which usually leaves the
ophthalmic artery near its exit from the optic canal
y It accompanies the lacrimal nerve along the upper border of
lateral rectus, supplies and traverses the lacrimal gland, and
ends in the eyelids and conjunctiva as the lateral palpebral
arteries
y Lacrimal artery gives off one or two zygomatic branches
y One reaches the temporal fossa via the zygomaticotemporalforamen, and anastomoses with the deep temporal arteries.
y The other reaches the cheek by the zygomaticofacial
foramen, and anastomoses with transverse facial arteries
y A recurrent meningeal branch, usually small, passes back via
the lateral part of the superior orbital fissure to anastomosewith a middle meningeal branch
-
8/7/2019 Optic nerve and opthalmic artery
31/45
-
8/7/2019 Optic nerve and opthalmic artery
32/45
y The supraorbital artery leaves the ophthalmic artery where it crosses
the optic nerve
y Ascends medial to superior rectus and levator palpebrae superioris
y It passes through the foramen and divides into superficial and deep
branches which supply the skin, muscles and frontal periosteum
y It supplies superior rectus and levator palpebrae superioris, and sends
a branch across the trochlea to the medial canthus
y The posterior ethmoidal artery runs through the posterior ethmoidalcanal and supplies the posterior ethmoidal air sinuses
-
8/7/2019 Optic nerve and opthalmic artery
33/45
-
8/7/2019 Optic nerve and opthalmic artery
34/45
-
8/7/2019 Optic nerve and opthalmic artery
35/45
y The anterior ethmoidal artery passes with its accompanyingnerve through the anterior ethmoidal canal to supply ethmoidal
and frontal air sinusesy The supratrochlear artery is a terminal branch of the ophthalmic
artery
y It leaves the orbit superomedially with the supratrochlear nerve,
ascends on the forehead to supply the skin, muscles andpericranium, and anastomoses with the supraorbital artery andwith its contralateral fellow
-
8/7/2019 Optic nerve and opthalmic artery
36/45
-
8/7/2019 Optic nerve and opthalmic artery
37/45
Applied
y Optic neuritis is inflammation of the optic nerve.
y It may cause sudden, reduced vision in the affected eye
y Sudden inflammation of the nerve connecting the eye and the
brain (optic nerve) can injure the insulation surroundingeach nerve fiber, causing the nerve to swell
-
8/7/2019 Optic nerve and opthalmic artery
38/45
y Optic neuritis most commonly develops due to an autoimmune
disorder that may be triggered by a viral infection, vitamin B
deficiency
y Ocular stroke commonly is caused by embolism of the retinal artery
y Retinal artery occlusion represents an ophthalmologic emergency, and
delay in treatment may result in permanent loss of vision
y Acutely, obstruction of the central retinal artery results in inner layer
edema and damage of the ganglion cell nuclei
-
8/7/2019 Optic nerve and opthalmic artery
39/45
-
8/7/2019 Optic nerve and opthalmic artery
40/45
y The ciliary ganglion is a parasympathetic ganglion which is concernedfunctionally with the motor innervation of certain intraocular muscles
y It is a small, flat, reddish-grey swelling, 1-2 mm in diameter,connected to the nasociliary nerve,
y located near the apex of the orbit in loose fat c.1 cm in front of themedial end of the superior orbital fissure
y It lies between the optic nerve and lateral rectus, usually lateral to theophthalmic artery
y Its neurones, which are multipolar, are larger than in typicalautonomic ganglia; a very small number of more typical neurones arealso present
-
8/7/2019 Optic nerve and opthalmic artery
41/45
-
8/7/2019 Optic nerve and opthalmic artery
42/45
-
8/7/2019 Optic nerve and opthalmic artery
43/45
-
8/7/2019 Optic nerve and opthalmic artery
44/45
-
8/7/2019 Optic nerve and opthalmic artery
45/45
y Its connections or roots enter or leave it posteriorly
y Eight to ten delicate filaments, termed the short ciliary nerves,emerge anteriorly from the ganglion arranged in two or three bundles,the lower being larger
y They run forwards sinuously with the ciliary arteries, above and belowthe optic nerve, and divide into 15-20 branches
y Pierce the sclera around the optic nerve and run in small grooves onthe internal scleral surface
y They convey parasympathetic, sympathetic and sensory fibres betweenthe eyeball and the ciliary ganglion: only the parasympathetic fibressynapse in the ganglion