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The human eye is a complex organ, and its movement is controlled by six external muscles, which work in pairs. These muscles are responsible for directing the eyes side-to-side, up and down, or diagonally. They are also involved in binocular movements, where both eyes turn in unison, a phenomenon known as yoking. The muscles that control eye movement are called extraocular muscles and are divided into two groups: the four recti muscles and the two oblique muscles. These muscles originate from the common tendinous ring, a ring of fibrous tissue surrounding the optic canal at the back of the orbit, and attach to the sclera of the eyeball. The recti muscles are named for their straight path from origin to attachment, while the oblique muscles take an angular approach to the eyeball.
| Characteristics | Values |
|---|---|
| Number of muscles involved in eyeball movement | 6 |
| Types of muscles | Recti and oblique |
| Recti muscles | Superior rectus, inferior rectus, medial rectus, and lateral rectus |
| Oblique muscles | Superior oblique and inferior oblique |
| Innervation | Oculomotor nerve (CN III), Trochlear nerve (CN IV), and Abducens nerve (CN VI) |
| Function | Control which way the eyes point, enabling binocular single vision |
| Movement | Horizontal, vertical, and torsional |
| Horizontal movement | Adduction (toward the nose) and abduction (away from the nose) |
| Vertical movement | Elevation and depression |
| Torsional movement | Intorsion (bringing the top of the eye toward the nose) and extorsion (bringing the top of the eye away from the nose) |
| Movement disorders | Myotonic dystrophy, oculopharyngeal muscular dystrophy (OPMD), Kearns-Sayre syndrome, thyroid eye disease, and Graves' disease |
| Injuries | Skull fractures, eye injuries, and head injuries |
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What You'll Learn
How many muscles control eye movement?
Six muscles are involved in controlling the movement of the human eyeball. These muscles are responsible for directing the eyes side-to-side, up and down, or at diagonal angles. They are also responsible for the movement of the eyes into different gazes.
The six muscles can be divided into two groups: the four recti muscles and the two oblique muscles. The four recti muscles are the superior rectus, inferior rectus, medial rectus, and lateral rectus. They are called recti, which is Latin for "straight," because they have a direct path from origin to attachment. The two oblique muscles are the superior oblique and inferior oblique, which have an angular approach to the eyeball.
The extraocular muscles are the most specialized skeletal muscles in the human body. They can be broadly divided into voluntary and involuntary muscles. The voluntary muscles include the four recti muscles, two oblique muscles, and levator palpebrae superioris. The levator palpebrae superioris is responsible for eyelid elevation. The involuntary muscle group includes the superior tarsal muscle (Müller's muscle), inferior tarsal muscle, and orbitalis.
The extraocular muscles are innervated by three cranial nerves: the oculomotor nerve (CN III), the trochlear nerve (CN IV), and the abducens nerve (CN VI). These nerves control the movements of the superior, inferior, and medial rectus muscles, as well as the inferior and superior oblique muscles. Damage to one of these cranial nerves will cause paralysis of its respective muscles and alter the resting gaze of the affected eye.
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What are the names of these muscles?
The muscles that control eye movement are called extraocular muscles. There are six of them, and they can be divided into two groups: the four recti muscles and the two oblique muscles.
The four recti muscles are the superior rectus, inferior rectus, medial rectus, and lateral rectus. They are called recti, which is Latin for "straight", because they have a direct path from origin to attachment. The recti muscles control horizontal eye movements: the medial rectus is responsible for adduction (movement towards the nose), and the lateral rectus is responsible for abduction (movement away from the nose). When the eye is abducted, the rectus muscles are the prime vertical movers.
The two oblique muscles are the superior oblique and inferior oblique. Unlike the recti muscles, the oblique muscles do not originate from the common tendinous ring and instead take an angular approach to the eyeball. They are responsible for torsional movements and are the prime vertical movers when the eye is adducted. The superior oblique muscle is supplied by the trochlear nerve (cranial nerve IV), while the inferior oblique muscle is controlled by the oculomotor nerve (cranial nerve III).
In addition to these six muscles, there is also the levator palpebrae superioris, which is responsible for eyelid elevation.
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What types of eye movement do they control?
Six muscles are involved in controlling the movement of the human eyeball. These muscles can be divided into two groups: the four recti muscles and the two oblique muscles. The four recti muscles are the superior rectus, inferior rectus, medial rectus, and lateral rectus. The two oblique muscles are the superior oblique and inferior oblique.
The recti muscles are so named because they follow a direct path from origin to attachment, in contrast to the oblique muscles, which take an angular approach to the eyeball. The recti muscles originate from the common tendinous ring, a ring of fibrous tissue that surrounds the optic canal at the back of the orbit, and attach to the sclera of the eyeball.
The lateral and medial rectus muscles control horizontal movements of the eye, either toward the nose (adduction) or away from the nose (abduction). Vertical movements, such as elevation and depression, require the coordinated action of the superior and inferior rectus muscles, along with the oblique muscles. When the eye is abducted, the rectus muscles are the primary vertical movers, while the oblique muscles take the lead when the eye is adducted.
The oblique muscles are also primarily responsible for torsional movements, which bring the top of the eye toward or away from the nose (intorsion and extorsion, respectively). The superior oblique muscle is supplied by the trochlear nerve (cranial nerve IV), while the lateral rectus muscle is innervated by the abducens nerve (cranial nerve VI). The oculomotor nerve (cranial nerve III) controls the movements of the superior, inferior, and medial rectus muscles, as well as the inferior oblique muscle.
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What happens when these muscles are damaged?
The eye muscles are delicate, and damage to them can have serious consequences. Ophthalmoplegia, or paralysis of the eye muscles, can affect one or more of the six muscles that hold the eye in place and control its movement. This can lead to double vision, blurred vision, and an inability to position the eyes in sync. It can also cause drooping eyelids and difficulty controlling the muscles that coordinate the eyes.
There are two types of ophthalmoplegia: chronic progressive external ophthalmoplegia and internal ophthalmoplegia. Chronic progressive external ophthalmoplegia typically appears in adults between the ages of 18 and 40 years. It usually starts with drooping eyelids and difficulty controlling the eye muscles. Internal ophthalmoplegia is caused by nerve damage to the nerve fibers that coordinate lateral eye movement, resulting in double vision.
Damage to the oculomotor nerve (CN III) will result in the paralysis of most of the extraocular muscles, except the lateral rectus and superior oblique. The affected eye will be displaced laterally and inferiorly, adopting a position known as 'down and out'. This will cause ptosis, a dilated pupil, and lateral strabismus in the denervated eye. A lesion of the oculomotor nerve can also lead to Horner's syndrome, which includes symptoms such as partial ptosis, miosis, and anhidrosis on the ipsilateral side of the face.
Damage to the trochlear nerve (CN IV) will paralyze the superior oblique muscle. Although this may not affect the resting orientation of the eyeball, the patient will experience diplopia (double vision) and may develop a head tilt away from the site of the lesion to bring the visual axis of the partially paralyzed eye into alignment with the normal eye.
A lesion of the abducens nerve (CN VI) will paralyze the lateral rectus muscle, causing the affected eye to be adducted by the resting tone of the medial rectus. This will result in an abnormality of conjugate horizontal eye movements called lateral gaze paralysis.
In addition to these specific nerve lesions, damage to the lower motor neurons that innervate an extraocular muscle can result in flaccid paralysis of the muscle, while damage to upper motor neurons will produce deficits only in selective types of movements, such as smooth pursuit.
Eye muscle conditions can be caused by injuries to the eye, skull, or other surrounding tissues. Skull fractures can be particularly dangerous, as the eye muscles can become stuck in the crack, requiring immediate surgery to prevent permanent damage. Certain conditions, such as myotonic dystrophy, oculopharyngeal muscular dystrophy (OPMD), Kearns-Sayre syndrome, thyroid eye disease, and Graves' disease, can also directly weaken the eye muscles.
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What is the treatment for eye muscle damage?
There are six muscles that control the movement of the eyeball, which can be divided into two groups: the four rectus muscles and the two oblique muscles. These muscles are responsible for movements of the eye along three different axes: horizontal, vertical, and torsional.
Eye muscle damage can be caused by various factors, including injuries to the eye, face, or head, skull fractures, and underlying medical conditions. Treatment for eye muscle damage depends on the underlying cause and can vary from conservative management to surgical intervention. Here is an overview of the treatments for eye muscle damage:
Conservative Management
- Eye protection: Wearing goggles or impact-resistant glasses can help prevent eye muscle damage caused by injuries.
- Medications: Certain medications may be prescribed, depending on the specific condition affecting the eye muscles.
- Eye exercises: In some cases, eye muscle disorders can be managed or improved through eye exercises.
- Eyeglasses: Corrective eyeglasses can help treat underlying conditions, such as strabismus, and improve eye muscle function.
Surgical Intervention
Eye muscle repair surgery is typically considered when conservative treatments are ineffective or insufficient. This procedure corrects muscle imbalances that cause the eyes to cross inward or outward (strabismus). During the surgery, the doctor will manipulate the eye muscles to realign the eyes and restore proper eye movement. It is usually performed as an outpatient procedure, allowing patients to return home the same day. However, post-operative care is crucial, and patients should avoid touching or rubbing their eyes to prevent infection. Antibiotic eye drops or ointments may be prescribed as a precautionary measure.
In conclusion, the treatment for eye muscle damage depends on the underlying cause and can range from conservative management, such as eye protection, medications, and eye exercises, to surgical intervention in more severe or refractory cases. It is important to seek medical attention for any eye movement issues, as they can be indicative of underlying conditions, and prompt treatment can help prevent permanent vision loss.
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Frequently asked questions
There are six muscles involved in the control of the eyeball itself.
The six muscles can be divided into two groups: the four recti muscles, and the two oblique muscles. The four recti muscles are the superior rectus, inferior rectus, medial rectus and lateral rectus. The two oblique muscles are the superior oblique and inferior oblique.
Damage to the muscles that control eye movement can cause paralysis of the eyes, double vision, and in some cases, can be a sign of a serious medical condition.
