L15 EOMs Flashcards
What is the fascial sheath aka orbital fascia?
Modified conjunctiva that forms the periosteum of the bones of the orbit. All structures that can be isolated in the orbit are covered by fascial sheath, except optic nerve. It is continuous with dura matter of optic nerve, and continuous with orbital septum
It surrounds all organs and muscles within orbit from fat and other stuff.
i.e. around rectus muscle and eyeball
The superior and inferior rectus, along with oblique muscles attach at an angle, and therefore have … actions
tertiary
Fascial sheath also forms the … capsule (is the same thing as)
Tenon’s capsule
What do the check ligaments do?
Prevents eye from going inwards
What is the Tenon’s capsule?
aka facia bulbi or bulbar sheath
Fascial sheath that envelops eyeball, separating it from orbital fat. Blood vessels and nerves that approach the eyeball pierce through the capsule.
Function: position and support eyeball. Permits the action of EOMs which are attached to the Tenon’s capsule.
Fascial sheath is separated from the sclera by ___ space
Episcleral
Anteriorly, the fascial sheath is attached to…
Sclera
Posteriorly, the fascial sheath fuses with the…
Meninges around optic nerve
The modified tenon’s capsule has expansions around…
EOMs, medial and lateral check ligaments, and around the ligament of lockwood.
What do check ligaments do?
Limit the action of the medial and lateral rectus, and prevent retraction of the globe into the orbital cavity during eye movements.
Where are the check ligaments attached to?
Attached to the lateral wall of the orbital, lacrimal, and zygomatic bones.
The suspensory ligament (of lockwood) is formed by…
Blending of the fascial sheaths o the inferior rectus and inferior oblique bmuscles with part of Tenon’s capsule.
What is the name of the structure from which the superior oblique’s tendon runs between?
Trochlea
Trochlea is fibrocartilage attached to the ____ of the frontal bone
trochlear fossa
Inferior oblique arises from the ___ bone (in front of the orbit), and inserts into the ___ side of the globe
posterior, inferior, lateral surface of the globe.
What is the acronym used to remember EOM innervation?
LR6(SO4)3
Annulus of Zinn is a…
Tendinous ring at the apex of the orbital cavity, where rectus and superior oblique muscles arise from.
Located in front of the superior orbital fissure.
Cranial Nerve __ leaves the orbit through Annulus of Zinn. Other CN pass into the orbit through the annulus
3
What is the agonist?
Primary muscle that moves an eye in a given direction
What is a Synergist?
A muscle in the same eye that moves in the same direction as the agonist
What is an anagonist?
The muscle in the same eye that moves in the opposite direction of the agonist.
What is the listing’s law?
Listings’ law states that the eye achieves all 2D orientations starting from one specific “primary” reference orientation, then rotating about an axis that lies within the plane orthogonal to the primary orientation’s gaze direction.
What is hering’s law?
Equal innervation to muscle of both eyes gazing in a particular direction
What is sherrington’s law?
When one muscle constricts in the eye, the other antagonist muscle relaxes in the same eye.
What is Axes of Fick?
A movement around an eye around the theoretical enter of rotation. They rotate about 3 potential axes. Ficks’ axes cross at the centre of rotation.
Horizontal eye movements around z axis
vertical eye movements around x axis
Torsional eye movements around y-axis.
What are yoke muscles?
Primary muscles in each eye that accomplish a given version (i.e. for a right gaze, the right lateral rectus and left medial rectus). By herring’s law, yoke muscles are given equal and simultaneous innervation.
What is the secondary action of SR?
Intorsion
What is the secondary action of IR?
Extorsion
What is the secondary action of IO?
Elevation
What is the secondary action of SO?
Depression
What is the tertiary action for SR and IR?
Adduction
What is the tertiary action for IO and SO?
Abduction
What is strabismus/heterotropia?
If one eye is constantly in a different direction than the eye that is fixating
What is nystagmus?
Involuntary, rapid eye movement (physiological - optic kinetic nystagmus (OKN), vestibuloocular reflex, albinism) or (pathological - drug induced)
