Download Eye & Orbit

Identify the elements of the bony orbit on a skull or x-ray.
Indicate the structures lying superior, inferior, medial and lateral to the
eyeball and the position of the eyeball relative to the bony orbit.
Horizontal CT
Orbit lies:
• Lateral to nasal cavity and
paranasal sinuses
•Medial to infratemporal fossa
Coronal CT
Orbit lies:
• Inferior to cranial cavity
•Above maxillary sinus
Eyeball is oriented anteroposteriorly but orbits are angled outward
Trace the flow of blood into and out of the orbit and orbital
structures.
Supratrochlear a.
Supra-orbital a.
Lacrimal gland
Sup. Ophthalmic v.
Inf. Ophthalmic v.
Ant. ethmoidal a.
Cavernous sinus
Post. ethmoidal a.
Lacrimal a.
Facial v.
Ophthalmic a.
Internal carotid a.
Retromandibular v.
Pterygoid plexus
Identify the extra-ocular muscles.
Side view
Levator palpebrae
Superior oblique
Optic nerve
Superior rectus
Lateral rectus (cut)
Inferior oblique
Inferior rectus
Medial rectus
SO
LP
LP
SR
LP
SO
MR
IO
SR
SR
SO
LR
MR
IR
IO
LR
LR
MR
IR
IR
Frontal views
IO
Indicate the nerve supply to each.
Supratrochlear n.
Supra-orbital n.
Lacrimal n.
Infratrochlear n.
Ethmoidal nn.
Lacrimal n.
Frontal n.
Short ciliary nn.
V1
VI
Long ciliary nn.
Nasociliary n.
V2
II
Ciliary ganglion
V3
V
II
III
Frontal n. (cut)
III
IV VI
V
IV
VI
Sensory nerves are branches
of the ophthalmic division
of the trigeminal- V
1
Motor nerves are branches of
cranial nerves III, IV, and VI
Contrast the common clinical test for extra-ocular muscle function with
the action of the individual muscles.
SO
LP
Actions of individual extraocular muscles:
•Lateral & medial rectus pull eyeball medial &
laterally, respectively
SR
LR
MR
IR
•Because of different axis of orbit & eyeball, superior
& inferior rectus muscles pull the eyeball medially as
well as elevate and depress it
IO
•Because of their oblique course, the superior &
inferior oblique pull the eyeball laterally as well as
down and up
•Pure elevation is produced by the superior rectus &
inferior oblique acting together
•Pure depression is produced by IR & SO
Contrast the common clinical test for extra-ocular muscle function with
the action of the individual muscles.
Clinical tests:
•The best method to test eye motion is ask
the patient to follow your finger drawing a
large H pattern in the air a few feet from
their face. The two legs of the H will
isolate and test the motion of the
superior/inferior rectus pair and
inferior/superior oblique pair. The center
part of the H will test the medial and
lateral muscles.
•Obliques are unique and involve
adduction of globe prior to elevation and
depression
Predict the functional deficit resulting from damage to each nerve.
This patient has a damaged right trochlear nerve (IV). The right superior oblique muscle is
paralyzed. Note that movements to the right are not affected, but movements down and,
especially, down and to the left result in asymmetrical eye movements. The right eye is not
able to move down and in.
There is a very cool web site that allows you to simulate the eye motions expected from
lesions to different cranial nerves and different eye muscles. Check it out at
http://cim.ucdavis.edu/Eyes/Version1/eyesim.htm
Follow the course of autonomic nervous supply to the orbital
structures, indicating the pre- and post-ganglionic
sources of innervation.
To Eyeball:
•Preganglionic parasympathetic axons from EdingerWestphal nucleus travel in CN III to ciliary ganglion
•After synapsing in ciliary ganglion, postganglionic axons
travel to constrictor of the pupil and ciliary body via
short ciliary nerves
•Preganglionic sympathetic axons from T1-T2 enter
sympathetic chain and ascend to the superior cervical
ganglion (SCG)
•After synapsing in the SCG, postganglionic axons join
the plexus on the internal carotid artery and enter the
orbit via its ophthalmic branch
•In the orbit, these axons travel with the nasociliary
nerve. Some pass through the ciliary ganglion and
enter the eyeball via short ciliary nerves. Others enter
via long ciliary nerves. These innervate the dilator of
the pupil.
•Other sympathetic postganglionic axons contribute to
the innervation of the levator palpebrae muscle
Follow the course of autonomic nervous supply to the orbital
structures, indicating the pre- and post-ganglionic
sources of innervation.
Innervation of the lacrimal gland:
•Arises from facial nerve
•Takes pathway involving several nerves
Greater petrosal n.
N. of pterygoid canal formed from:
•parasympathetic preganglionic axons in
greater petrosal n. that will synapse in
pterygopalatine ganglion
•Sympathetic postganglionic axons from
SCG cells that will pass through ganglion
Facial n.
Lacrimal n. (V1)
Deep petrosal n.
V2
N. of pterygoid canal
Pterygopalatine ganglion
Pterygopalatine ganglion