There are six muscles that attach to the eyeball and control the voluntary movement of the eyes.
Six Extra Ocular Eye Muscles
The six muscles that control eye movements are called the extra ocular muscles. These muscles are around the eyeball and inside the eye socket.
The muscles are the superior rectus, medial rectus, lateral rectus, inferior rectus, superior oblique, and inferior oblique.
Four of these muscles have three functions in contributing to eye movement.
The Superior Rectus Muscle
The superior rectus muscle is an extra ocular muscle on the top of the eyeball.
The main function of the superior rectus muscle is to raise the eye when looking straight ahead.
The superior rectus muscle also assists moving the eyes towards the nose and turning the eye towards the nose.
If the superior rectus muscle is damaged, the eye will be unable to raise above the line of sight. This may cause the other eye to appear higher or the affected eye to appear lower.
The Medial Rectus Muscle
The medial rectus muscle is an extra ocular muscle on the side of the eyeball closest to the nose.
The function of the medial rectus muscle is to turn the eyeball towards the nose through a process called adduction.
The medial rectus muscle does not have a secondary or tertiary action.
Any damage to the medial rectus muscle will result in the inability to move the affected eye towards the nose.
The Lateral Rectus Muscle
The lateral rectus muscle is an extra ocular muscle on the side of the eyeball closest to the ear or edge of the face.
The function of the lateral rectus muscle is the opposite of the medial rectus. The lateral rectus muscle will turn the eyeball away from the nose and towards the side of the face which is called abduction.
Like the medial rectus, the lateral rectus does not have any additional functions.
If the lateral rectus muscle is damaged, the eye will be unable to turn past the midline towards the side of the face.
The Inferior Rectus Muscle
The inferior rectus muscle is an extra ocular muscle on the bottom of the eyeball which is responsible for moving the eyeball down when looking straight ahead.
The inferior rectus muscle also has additional actions that are less pronounced. The inferior rectus muscle can assist in moving the eye towards the nose and turning the eyeball away from the nose or towards the side of the face.
If the medial rectus is damaged, the eye will be unable to look down from straight ahead. Like the superior rectus, this may cause the eyes to appear misaligned.
The Superior Oblique Muscle
The superior oblique muscle is an extra ocular muscle on the top of the eyeball.
The superior oblique muscle inserts on the eyeball in the opposite direction of all of the recti muscles and as such has a different action.
The superior oblique muscle’s main action is to rotate the eye towards the nose.
The superior oblique muscle also assists in lowering the eyeball and moving the eye towards the side of the face.
If the superior oblique muscle is damaged, the eye will be unable to rotate inward without using the superior rectus muscle and as a result will compensate by lifting the eye.
In these cases, the eye with the damaged superior oblique muscle will appear higher than the other eye.
The Inferior Oblique Eye Muscle
The inferior oblique muscle is an extra ocular muscle that is on the bottom of the eyeball.
Like the superior oblique muscle, the inferior oblique inserts from the front to the back of the eyeball.
The main purpose of the inferior oblique muscle is to rotate the eyeball towards the side of the face or towards the ear.
The inferior oblique also assists in raising the eye and moving the eye towards the side of the face.
If the inferior oblique muscle is damaged, the eye will be unable to rotate outwards and may use the inferior rectus to compensate, resulting in the eye appearing lower than the other.
Functionality of the Extra Ocular Eye Muscles
The six extra ocular muscles work together to allow for quick, accurate eye movements.
It is important that each of the muscles is functioning properly to avoid symptoms such as double vision or an eye turning out.
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