Annulus of Zinn

Annulus of Zinn (also known as the annular tendon or common tendinous ring) is a crucial anatomical structure in the orbit. It serves as the origin for four of the six extraocular muscles that control the movements of the eye. Understanding the Annulus of Zinn is essential for medical professionals, particularly those specializing in ophthalmology and neurology, due to its significance in eye movement and its involvement in various pathological conditions.

Anatomy

The Annulus of Zinn is a fibrous ring situated at the apex of the orbit, surrounding the optic canal and part of the superior orbital fissure. It provides the origin for the four rectus muscles of the eye:

• Superior rectus
• Inferior rectus
• Medial rectus
• Lateral rectus

Additionally, it gives rise to the levator palpebrae superioris muscle, which is responsible for elevating the upper eyelid. The structure of the Annulus of Zinn is vital for the coordinated movement and stabilization of the eyeball, allowing for precise visual tracking and focus.

Function

The primary function of the Annulus of Zinn is to serve as an anchor point for the extraocular muscles. By providing a stable base, it enables the efficient and coordinated movement of the eye. This is crucial for binocular vision, allowing the eyes to move in a synchronized manner to focus on a single point in space.

Clinical Significance

The Annulus of Zinn is involved in several clinical conditions:

• Thyroid eye disease (TED): Inflammation and swelling of the muscles originating from the Annulus of Zinn can lead to restricted eye movement and proptosis (bulging eyes).
• Optic neuritis: Inflammation of the optic nerve, which passes through the center of the Annulus of Zinn, can result in pain and vision loss.
• Orbital tumors: Tumors in the vicinity of the Annulus of Zinn can affect the function of the extraocular muscles, leading to diplopia (double vision) and other visual disturbances.

Surgical Relevance

Knowledge of the Annulus of Zinn's anatomy is crucial during orbital surgeries, particularly in procedures involving the extraocular muscles or optic nerve. Surgeons must navigate carefully to avoid damaging these critical structures.

See Also

• Extraocular muscles
• Orbit
• Optic nerve
• Binocular vision