What is the role and function of extraocular muscles?

From the Guidelines

The extraocular muscles play a crucial role in controlling eye movements and positioning, and their proper functioning is essential for maintaining binocular vision, depth perception, and preventing diplopia (double vision) 1.

Role and Function of Extraocular Muscles

The extraocular muscles are responsible for moving the eyes in various directions, including up, down, left, right, and the diagonal movements. There are six muscles for each eye: the lateral rectus, medial rectus, superior rectus, inferior rectus, superior oblique, and inferior oblique. These muscles work together to produce the six cardinal directions of gaze and allow for smooth pursuit movements to track moving objects, saccadic movements for rapid eye repositioning, vergence movements to focus on objects at different distances, and vestibulo-ocular reflexes to maintain stable vision during head movements.

Importance of Extraocular Muscles

The extraocular muscles are innervated by three cranial nerves: the oculomotor (CN III), trochlear (CN IV), and abducens (CN VI) nerves. These muscles are unique compared to other skeletal muscles because they contain a high concentration of mitochondria, making them resistant to fatigue, which is essential for maintaining constant eye position and movement throughout the day. Proper functioning of these muscles is critical for binocular vision, depth perception, and preventing diplopia (double vision) 1.

Clinical Significance

Minimizing extraocular motility impairment, diplopia, and compensatory head position that can affect visual function, quality of life, and its socioeconomic consequences warrant treatment 1. The extraocular muscles can be affected by various conditions, including strabismus, thyroid eye disease, and iatrogenic strabismus, which can result in diplopia and other vision problems. Treatment options, such as surgery and botulinum toxin injections, are available to manage these conditions and improve vision outcomes 1.

Key Points

• The extraocular muscles control eye movements and positioning.
• There are six muscles for each eye: the lateral rectus, medial rectus, superior rectus, inferior rectus, superior oblique, and inferior oblique.
• The extraocular muscles are innervated by three cranial nerves: the oculomotor (CN III), trochlear (CN IV), and abducens (CN VI) nerves.
• Proper functioning of the extraocular muscles is critical for binocular vision, depth perception, and preventing diplopia (double vision).
• Treatment options, such as surgery and botulinum toxin injections, are available to manage conditions affecting the extraocular muscles.

From the Research

Extraocular Muscles

• Extraocular muscles are responsible for controlling the movement of the eyes
• There are six extraocular muscles for each eye, which work together to enable precise movements

Role and Function of Extraocular Muscles

• The primary function of extraocular muscles is to rotate the eyes in various directions, allowing for a wide range of vision
• They also play a crucial role in maintaining binocular vision and depth perception
• Extraocular muscles are controlled by the brain, which sends signals to the muscles to move the eyes in a coordinated manner

Treatment of Strabismus using Botulinum Toxin

• Botulinum toxin injection into extraocular muscles has been used as an alternative to strabismus surgery 2
• Studies have shown that botulinum toxin can be effective in treating strabismus, with success rates comparable to those of surgery 3, 4, 5
• The use of botulinum toxin has been found to reduce the duration of general anesthesia and time in the postanesthesia care unit compared to surgery 4

Comparison of Botulinum Toxin and Strabismus Surgery

• Research has compared the effectiveness of botulinum toxin injection and strabismus surgery in treating strabismus, with mixed results 3, 4, 5
• Some studies have found that botulinum toxin is noninferior to surgery at 36 months, while others have reported varying success rates 3, 4
• The choice between botulinum toxin and strabismus surgery may depend on individual patient factors and the type of strabismus being treated 3, 5

Adverse Events and Complications

• Botulinum toxin injection has been associated with adverse events such as partial transient ptosis and transient vertical deviation 3, 6
• However, these adverse events are typically temporary and resolve on their own 3, 6
• Strabismus surgery has also been associated with complications, including discomfort and the need for additional surgery 3