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The human eye is a complex organ that relies on several muscles to function properly. Each eye has six muscles that control its movement, and these muscles are known as extraocular muscles. These muscles work in pairs to enable the eyes to move in unison. The extraocular muscles are divided into two groups: rectus muscles and oblique muscles. The rectus muscles include the superior rectus, inferior rectus, medial rectus, and lateral rectus. The oblique muscles consist of the superior oblique and inferior oblique. These muscles work together to allow the eyes to move in different directions, such as up, down, left, and right. They also play a crucial role in maintaining proper eye alignment and enabling depth perception and three-dimensional vision. Understanding the anatomy and function of the eye muscles is essential for diagnosing and treating eye movement disorders, such as strabismus, where surgery may be required to correct muscle imbalances and restore normal vision.
| Characteristics | Values |
|---|---|
| Number of muscles controlling eye movement | 6 |
| Type of muscles | Extraocular muscles, Rectus muscles, Oblique muscles |
| Rectus muscles | Superior rectus, Inferior rectus, Medial rectus, Lateral rectus |
| Oblique muscles | Superior oblique, Inferior oblique |
| Cranial nerves controlling eye muscles | Cranial nerve III (oculomotor nerve), Cranial nerve IV (trochlear nerve), Cranial nerve VI (abducens nerve) |
| Function of superior rectus | Elevate the eye, Adduction, Intorsion |
| Function of inferior rectus | Depress the eye, Adduction, Extorsion |
| Function of lateral rectus | Abduct the eye |
| Function of medial rectus | Adduct the eye |
| Function of superior oblique | Depression, Adduction, Lateral rotation |
| Function of inferior oblique | Extorsion, Elevation, Abduction |
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What You'll Learn
Six muscles control eye movement
The movement of the eyeball is controlled by six muscles, which can be divided into two groups: the four rectus muscles and the two oblique muscles. These muscles are how you can direct your eyes side-to-side, up and down, or at diagonal angles. They are also responsible for eye synchronization, which enables certain visual capabilities like depth perception and three-dimensional (3D) vision.
The four rectus muscles are:
- Superior rectus: Top (“superior” means “up” or “top”)
- Inferior rectus: Bottom (“inferior” means “down” or “bottom”)
- Medial rectus: The side closest to your nose ("medial" means "middle," as in closer to your nose)
- Lateral rectus: The side farthest from your nose ("lateral" means "to the side," like where your ears are)
The two oblique muscles are:
- Superior oblique: This muscle works like a pulley, starting at the upper back of your eye and extending forward, then threading through a small bony opening on the upper-inner side of your eye socket.
- Inferior oblique: The inferior oblique attaches to the lower-inner side of your eye socket, extends laterally (away from your nose), wraps around the bottom of your eye, and attaches just behind the lateral rectus on the far side.
The six muscles work in pairs. When one muscle moves, its partner in the same eye helps control and balance that movement. This is why your eyes can only turn so far. There is also another type of paired movement involving both eyes, which experts call "yoking" because the eyes turn together like a pair of yoked horses or oxen.
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Rectus and oblique muscles
The eyes are controlled by six external muscles, which are also called "extrinsic" muscles. These muscles are responsible for eye movement and work in pairs. When one muscle moves, its partner in the same eye helps control and balance that movement. This is called "yoking", and it is how our eyes turn in unison.
There are two types of eye muscles: rectus muscles and oblique muscles. Each eye has four rectus muscles: superior rectus, inferior rectus, medial rectus, and lateral rectus. The superior rectus is at the top, the inferior rectus is at the bottom, the medial rectus is on the side closest to the nose, and the lateral rectus is on the side farthest from the nose. The recti muscles have a direct path from origin to attachment, which is where their name comes from, as "recti" is derived from the Latin word for "straight".
Each eye also has two oblique muscles. The superior oblique muscle works like a pulley, starting at the upper back of the eye and extending forward, then threading through a small, bony opening on the upper-inner side of the eye socket. The inferior oblique muscle attaches to the lower-inner side of the eye socket, extends laterally (away from the nose), wraps around the bottom of the eye, and attaches just behind the lateral rectus on the far side. Unlike the recti muscles, the oblique muscles have an angular approach to the eyeball.
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Cranial nerves and eye muscles
The eyes are controlled by six muscles that allow them to move in various directions. These muscles are extrinsic and external, attaching to the outside of the eyeball. They are:
- Superior rectus
- Inferior rectus
- Medial rectus
- Lateral rectus
- Superior oblique
- Inferior oblique
These muscles work in pairs, with one muscle moving and its partner controlling and balancing that movement. This is why human eyes can only turn so far. The muscles that control eye movement depend on signals that travel through three cranial nerves: cranial nerve III (CN III), also known as the oculomotor nerve; cranial nerve IV (CN IV), also known as the trochlear nerve; and cranial nerve VI (CN VI), also known as the abducens nerve.
Cranial nerve III controls the movements of the superior, inferior, and medial rectus muscles, as well as the inferior oblique muscle. Cranial nerve IV controls the superior oblique muscle. Cranial nerve VI is the most commonly affected by cranial nerve palsies, a specific type of nervous system-related muscle disorder.
The extraocular muscles are located within the orbit and are separate from the eyeball itself. They control the movements of the eyeball and the superior eyelid. There are seven extraocular muscles: the levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique, and superior oblique. The levator palpebrae superioris is the only muscle involved in raising the superior eyelid.
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Eye muscle conditions
There are several muscle disorders that affect eye movement, including myotonic dystrophy, oculopharyngeal muscular dystrophy (OPMD), Kearns-Sayre syndrome, thyroid eye disease, Graves' disease, strabismus (eye misalignment), and amblyopia (lazy eye). Strabismus is a disorder in which the two eyes do not line up in the same direction, resulting in "crossed eyes" or "walleye".
Nervous system-related disorders that can affect eye movement include cranial nerve palsies, myasthenia gravis, multiple sclerosis, stroke, transient ischemic attacks (TIAs), tumours and cancers of the brain, nerve or brain lesions, Lyme disease, Parkinson's disease, and parkinsonism. Sixth (abducens) nerve palsy is the most common form of cranial nerve palsy.
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Eye muscle surgery
The surgery involves detaching and reattaching the muscles to another position on the eye, either shortening or tightening them by cutting or folding them over. In some cases, the surgeon may move the muscle to make it looser. The muscles that control eye movement are all attached to the outside of the eyeball, and they are referred to as "external" or "extrinsic" muscles. There are six muscles involved in eye movement, four rectus muscles, and two oblique muscles. The rectus muscles include the superior rectus, inferior rectus, medial rectus, and lateral rectus. The two oblique muscles are the inferior oblique and superior oblique.
Before the surgery, the patient will have a pre-anesthesia visit, where they will be informed about when to stop eating and drinking. The patient will then be put under general anesthesia, and their vital signs will be monitored throughout the procedure. The surgeon will cut into the outer white covering of the eye (conjunctiva) and pull up the muscles that need surgery with a hook. They will then move the muscle as needed and attach the muscles with stitches (sutures) that dissolve. The surgery takes anywhere from 30 minutes to 2 hours.
After the surgery, the patient will be taken to a recovery room, where their vital signs will be monitored until they are discharged. The patient may need to rest and take it easy for up to a week, and they may be prescribed eye drops or ointment. The patient should also be informed about what to look out for after the surgery and when to call the doctor.
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Frequently asked questions
The human eye has six muscles that control its movement. These muscles are the superior rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, and inferior oblique. Each eye has four rectus muscles and two oblique muscles. The muscles work in pairs, with one muscle moving and the other controlling and balancing that movement.
The superior rectus elevates the eye, the inferior rectus depresses the eye, the lateral rectus abducts the eye, and the medial rectus adducts the eye.
The superior oblique intorts the eye and the inferior oblique extorts the eye.
