Extraocular Muscles + Eye Movements Flashcards
What are the axes of the eyes
Visual axis
Orbital axis
Insertion of extra ocular muscles
All insert into sclera
Why do we have two eyes?
- Stereoscopic vision (depth perception)
- Wider field of vision
What is stereoscopic vision?
Depth perception (3D)
What is conjugate gaze?
The movement of both eyes in the same direction synonymously
What is binocular vision?
The ability of both eyes to face the same direction + perceive a single 3D image **
What can you do to test if dipopia is due to misalignment of visual axes?
Covering over either eye > diplopia disappears
What are the extra ocular muscles of the eye?
Superior Rectus
Inferior Rectus
Medial Rectus
Lateral Rectus
Superior oblique
Inferior oblique
What is primary resting gaze?
Position of eyes when looking straight ahead
What axis do the extra ocular muscles run in line with?
Orbital axis
Innervation of the extra ocular muscles
LR6 SO4 R3
- lateral rectus: abducens CN VI
- superior oblique: trochlear CN IV
- rest: oculomotor CN III
Origin of the extra ocular muscles
- At the apex of the orbital cavity
- Rectus muscles come from the common tendinous ring
Describe the role of the extra ocular muscles at primary resting gaze
Equal and opposite pull of all extra ocular muscles
Describe the action of the extra ocular muscles when changing position of gaze
- Exert greater pull through action of certain extraocular muscles
- Antagonists relax
Action of superior rectus from primary resting gaze
Elevation
Intorsion
ADuction
Action of inferior rectus from primary resting gaze
Depression
Extorsion
ADuction
Action of medial rectus
ADduction
Action of lateral rectus
ABduction
Action of superior oblique from primary resting gaze
Intorsion
Depression
ABduction
Action of inferior oblique from primary resting gaze
Extorsion
Elevation
ABduction
Action of superior rectus when eye is positioned laterally
Elevation dominates
Action of inferior rectus when eye is position laterally
Depression dominates
Action of superior oblique when eye is positioned medially
Depression dominates
Action of inferior oblique when eye is positioned medially
Elevation dominates
What extra ocular muscles are stronger elevators ad depressors of the eyeball when the eye is in the ABducted (lateral) position?
Superior rectus E
Inferior rectus D
What extra ocular muscles are stronger elevators ad depressors of the eyeball when the eye is in the ADducted (medial) position?
Superior oblique D
Inferior oblique E
Define esotropic
Form of strabismus when one or both of the eyes turn inwards (ADducted)
Define hypertopia
A condition where one of the eyes is elevated
What is strabismus?
Ocular misalignment
(Squint)
Clinical testing of eye muscles
H movement to isolate + test each muscle
What is the likely cause of a oculomotor nerve issue if the pupil is spared?
Micro vascular ischameia
(Diabetes, hypertensive)
How to remember the actions of the oblique extra ocular muscles?
oBlique - aBduction
Oblique - Opposite (superior depresses, inferior elevate)
Superior oblique - depression + ABduction
Inferior oblique - elevation + ABduction
What is the position of the eye in a trochlear nerve lesion?
Up + in
Superior oblique innervation lost (depression + ABduction)
What is the position of the eye in oculomotor nerve lesion?
Down + out
Lateral rectus + superior oblique still work (ABduction + depression)
What could causes micro vascular ischaemia?
Diabetes
Hypertension
