Definition: Muscles responsible for eye movement, allowing coordinated tracking of objects.
Importance: Ensure accurate visual perception; coordinating eye movements is crucial for effective vision.
Six main extrinsic eye muscles control eye movements:
Lateral Rectus Muscle: Moves the eye outward, away from the nose.
Medial Rectus Muscle: Moves the eye inward, toward the nose.
Superior Rectus Muscle: Elevates the eye, moving it upward.
Inferior Rectus Muscle: Depresses the eye, moving it downward.
Superior Oblique Muscle: Rotates the eye downward and away from the nose.
Inferior Oblique Muscle: Rotates the eye upward and away from the nose.
Innervated by three cranial nerves:
Oculomotor Nerve (Cranial Nerve III): Controls most extrinsic muscles.
Trochlear Nerve (Cranial Nerve IV): Innervates the superior oblique muscle.
Abducens Nerve (Cranial Nerve VI): Innervates the lateral rectus muscle.
Essential for binocular vision, depth perception, and visual tracking.
Conjugate eye movement: When both eyes move together harmoniously.
Disruptions can lead to diplopia (double vision) and focusing difficulties.
Convergence: Both eyes move inward to focus on near objects (e.g., reading).
Divergence: Both eyes move outward to focus on distant objects.
Various conditions can affect eye functioning:
Strabismus: Condition where eyes misalign (crossed eyes), leading to potential double vision.
Nystagmus: Involuntary, repetitive eye movements, often linked to neurological disorders.
Extraocular muscles are active during REM sleep, involving rapid eye movements linked to dreaming.
Finger tracking test: Checks coordination of eye muscles for abnormalities.
Diagnostic techniques include:
Hirschberg Test: Light source checks eye alignment.
Cover Test: Assesses eye muscle disorders via occlusion.
Exercises and vision therapy can improve eye coordination and strengthen eye muscles for individuals with control difficulties.
Understanding these muscles aids in perceiving and interacting with the world.
Illustrates the arrangement and connections of extrinsic eye muscles.
Muscle | Movement Description | Target Direction | Prime Mover | Origin | Insertion |
---|---|---|---|---|---|
Superior Rectus | Moves eyes up and inward (elevates and adducts) | Medial | Superior rectus | Common tendinous ring (optic foramen) | Superior surface of the eyeball |
Inferior Rectus | Moves eyes down and inward (depresses and adducts) | Medial | Inferior rectus | Common tendinous ring (optic foramen) | Inferior surface of the eyeball |
Lateral Rectus | Moves eyes outward (abducts) | Lateral | Lateral rectus | Common tendinous ring (optic foramen) | Lateral surface of the eyeball |
Medial Rectus | Moves eyes inward (adducts) | Medial | Medial rectus | Common tendinous ring (optic foramen) | Medial surface of the eyeball |
Superior Oblique | Rotates eyes downward and outward (depresses) | Lateral | Superior oblique | Sphenoid bone | Surface of eyeball between inferior and lateral rectus |
Inferior Oblique | Rotates eyes upward and outward (elevates) | Lateral | Inferior oblique | Floor of orbit (maxilla) | Surface of eyeball between inferior and lateral rectus |
Levator Palpebrae Superioris | Raises upper eyelid | Upper eyelid | Levator palpebrae | Roof of orbit (sphenoid bone) | Skin of upper eyelids |
Orbicularis Oculi | Closes eyelids | Eyelid | Orbicularis oculi | Medial bones of orbit | Circumference of orbit |