Anatomy of the Eye

Cornea

• Transparent, dome-shaped surface at the front of the eye
• Refracts light, allowing it to enter the eye
• Composed of five layers: epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium
• Regenerates quickly, with the entire epithelium replaced every 7-10 days

Retina

• Innermost layer of the eye, lining the back of the eye
• Contains specialized light-sensitive cells (photoreceptors: rods and cones) that convert light into electrical signals
• Divided into two parts: outer plexiform layer and inner nuclear layer
• Rods responsible for peripheral and night vision, cones responsible for color vision and high-acuity central vision

Lens

• Transparent, flexible structure behind the iris
• Changes shape to focus light on the retina (accommodation)
• Composed of crystalline proteins (crystallins) that provide refractive power
• Suspended by zonular fibers, which attach to the ciliary body

Iris

• Colored part of the eye, controlling the amount of light entering the eye
• Composed of smooth muscle and connective tissue
• Regulates pupil size through contraction and relaxation of the iris muscles (dilator and sphincter pupillae)

Optic Nerve

• Cranial nerve responsible for transmitting visual information from the eye to the brain
• Composed of axons from the ganglion cell layer of the retina
• Divided into four parts: intraocular, intraorbital, intracanicular, and intracranial

Blood Supply

• Ophthalmic artery: main artery supplying the eye
• Central retinal artery: branches from the ophthalmic artery, supplying the retina
• Choroidal circulation: supplies the choroid, a layer of blood vessels between the sclera and retina

Innervation

• Oculomotor nerve (CN III): controls extraocular muscles, eyelid movement, and pupil constriction
• Trochlear nerve (CN IV): controls superior oblique muscle
• Abducens nerve (CN VI): controls lateral rectus muscle
• Trigeminal nerve (CN V): provides sensory innervation to the eye and surrounding areas

Ciliary Body

• Ring-shaped structure behind the iris, responsible for producing aqueous humor
• Composed of ciliary muscles, ciliary epithelium, and zonular fibers
• Aqueous humor production and drainage regulate intraocular pressure

Cornea

• The transparent, dome-shaped surface at the front of the eye that refracts light allowing it to enter the eye
• Composed of five layers: epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium
• Has a rapid regeneration process, replacing the entire epithelium every 7-10 days

Retina

• The innermost layer of the eye, lining the back of the eye, containing specialized light-sensitive cells (photoreceptors: rods and cones)
• Photoreceptors convert light into electrical signals, with rods responsible for peripheral and night vision, and cones responsible for color vision and high-acuity central vision
• Divided into two parts: outer plexiform layer and inner nuclear layer

Lens

• A transparent, flexible structure behind the iris that changes shape to focus light on the retina (accommodation)
• Composed of crystalline proteins (crystallins) providing refractive power
• Suspended by zonular fibers, which attach to the ciliary body

Iris

• The colored part of the eye, controlling the amount of light entering the eye through contraction and relaxation of the iris muscles (dilator and sphincter pupillae)
• Composed of smooth muscle and connective tissue

Optic Nerve

• The cranial nerve responsible for transmitting visual information from the eye to the brain
• Composed of axons from the ganglion cell layer of the retina
• Divided into four parts: intraocular, intraorbital, intracanicular, and intracranial

Blood Supply

• The ophthalmic artery is the main artery supplying the eye
• The central retinal artery branches from the ophthalmic artery, supplying the retina
• The choroidal circulation supplies the choroid, a layer of blood vessels between the sclera and retina

Innervation

• The oculomotor nerve (CN III) controls extraocular muscles, eyelid movement, and pupil constriction
• The trochlear nerve (CN IV) controls the superior oblique muscle
• The abducens nerve (CN VI) controls the lateral rectus muscle
• The trigeminal nerve (CN V) provides sensory innervation to the eye and surrounding areas

Ciliary Body

• A ring-shaped structure behind the iris, responsible for producing aqueous humor
• Composed of ciliary muscles, ciliary epithelium, and zonular fibers
• Aqueous humor production and drainage regulate intraocular pressure