Eye Muscles Anatomy Quiz

Tear Film

• The outermost layer of the tear film is composed of lipids
• Lipids prevent tear evaporation
• Lipids provide lubrication for smooth lid movement
• Lipids contribute to the optical properties of the eye
• Lipids maintain a continuous strip at the lid margin to prevent tear overflow by increasing surface tension

Middle Aqueous Layer

• The middle layer of the tear film is the aqueous layer
• The aqueous layer provides oxygen to the avascular parts of the eye
• The aqueous layer provides an antibacterial environment to the eye
• The aqueous layer helps maintain a smooth surface by filling in irregularities
• The aqueous layer washes away debris towards the puncta (drainage points)

Innermost Muцин Layer

• The innermost layer of the tear film is the mucin layer
• The mucin layer interacts with the lipid layer to stabilize the tear film
• The mucin layer collects loose cells, foreign particles, and bacteria to the bulbar conjunctiva.

Conjunctiva

• The conjunctiva is a thin, transparent mucous membrane
• It lines the posterior surfaces of the eyelids.
• The conjunctiva covers the anterior surface of the eyeball, but excludes the cornea
• The conjunctiva secretes mucus to lubricate the eye
• The conjunctiva has two parts: bulbar and palpebral, and a transitional region called forniceal conjunctiva

Eye Muscles

• Six muscles surround the eye (four straight, two oblique)
• These muscles control eye movement (adduction and abduction, elevation/depression, and intorsion/extorsion).
• Eye muscles are responsible for turning and moving the eye
• Each muscle contracts and relaxes at the same time

Eye Movement Types

• Adduction: Eye moves towards the nose
• Abduction: Eye moves away from the nose
• Elevation: Eyes look upward
• Depression: Eyes look downward
• Intorsion: Top of the eye turns inwards
• Extorsion: Top of the eye turns outwards

Three Antagonistic Pairs of Eye Muscles

• Lateral and medial rectus muscles (horizontal movement)
• Superior and inferior rectus muscles (vertical movement)
• Superior and inferior oblique muscles (vertical and torsional movements).

Strabismus

• Strabismus is a condition where the eyes do not properly align
• One type is esotropia, where the eye turns inwards.
• Another type is exotropia, where the eye turns outwards.
• Other types include hypotropia (downward turning) and hypertropia (upward turning).