8.2.1 Extraocular Muscles Flashcards
Why do we have binocular vision?
Wider field of vision
Depth perception 3D vision (stereoscopic vision)
What needs to happen to allow binocular vision?
Visual axis of both eyes must be aligned
Eyes need to co-ordinate and move together conjugate eye movement so that the two images that reach the occipital cortex are fused
What happens if the visual axis are not aligned?
Brain unable to fuse the two images as they hit different parts of each retina, thus two images are seen
Diplopia
What are the extra-ocular muscles in each eye?
4 recti muscles:
- Superior rectus
- Inferior rectus
- Lateral rectus
- Medial rectus
2 obliques:
- Superior oblique
- Inferior oblique
Where do all extra-ocular muscles attach?
Sclera
Where do all EO muscles originate?
Apex of the orbit, except IO which arises from floor of orbital cavity anteriorly
Where do the recti muscles arise from?
Common tendinous ring
What innervates the EO muscles?
Remember trochlear (CNIV) does superior oblique, abducens (CNVI) does lateral rectus so oculomotor does the rest
What are the two axis of the eye?
Axis of the orbit (EO muscles run in line with this and thus some attach obliquely)
Visual axis
(Don’t align fully)
What is the trochlear pulley?
Ring-like cartilage through which superior oblique passes
What muscles are acting in primary resting gaze?
All EO muscles, equal and opposite pull
Actions are balanced at rest, each muscle has an antagonist of its movement
How do we change the position of our gaze?
Muscles moving both eyes must be highly co-ordinated and move simultaneously
Visual axes must remain aligned (conjugate gaze)
What is intorsion and extorsion?
Internal rotation and external rotation
What muscles have a single action on the eye?
Medial and lateral recti
