EYEBALL

EYEBALL (SIMPLE EYE)

• Eyeball is made up of 3 coats:

1. Fibrous coat (outermost layer):

• Anterior 1/6th is transparent & called Cornea.
• Posterior 5/6th is opaque & called Sclera.

2. Vascular coat (middle layer):

Consist of, from anterior to posterior: Iris, ciliary body & choroid.

3. Nervous coat (inner most): Consists of retina.

•  Within these coats are the aqueous humor (in anterior segments), the lens, and the vitreous humor (in posterior segment). 

SEGMENTS & CHAMBERS OF EYEBALL

• Eyeball is divided into 2 segments:

A) Anterior segment

• Part of eyeball anterior to posterior border of lens is called anterior segment.
• It consists of lens, & structures anterior to it, i.e., cornea, iris & two aqueous humor-filled spaces, i.e., anterior & posterior chambers.

i) Anterior chambers:

• bounded anteriorly by back of cornea 
• posteriorly by the iris & part of ciliary body.
• It contains aqueous humor.

ii) Posterior chamber: Triangular chamber

• bounded antrerorly by the posterior surface of the iris & ciliary body
• poteriorly by the lens & it zonules.
• It aso contains aqueous humor.

→ Thus both anterior & posterior chambers are part of anterior segment & both contain aqueous humor.

 B) Posterior segment

• Part of eyeball posterior to lens is called posterior segment.
• It consists of vitreous humor, retina, choroid & optic disc. 

Orbit, extraocular muscles & appendages of the eye

• Each eyeball is suspended by extraocular muscles & fascial sheaths in a quadrilateral pyramid shaped bony cavity called orbit.
• Each eye is protected anteriorly by two shutters called eyelids.
• The anterior part of sclera & posterior surface of lids are lined by thin membrane called conjunctiva.
• For smooth functioning of conjunctiva & cornea, tearsare produced by the lacrimal glands.
• These structures are collectively called the appendages of the eye & include eyelids, eyebrows, conjunctiva, lacrimal apparatus.
• The suspensory ligament (of lockwood) is a part of fascial sheath of eyeball. It provides inferior stability to the eyeball.

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