Ocular Anatomy

What is OD?

Right eye

What is OS?

Left eye

What is OU?

Both eyes

What animals have a enclosed boney orbit?

Cows, sheep, horses, goats, primates

What animals have open orbits?

Pigs and carnivores with a supraorbital ligament between frontal and zygomatic bones

What does the oculomotor nerve innervate?

Most of the eye muscles

What does the trochlear nerve innervate?

Dorsal oblique muscle

What does the abducens innervate?

Retractor bulbi muscle and lateral rectus

Where is the optic nerve located?

Ventral and lateral

How do the rectus muscles work?

Pull the eye in the direction their name implies (dorsal goes up)

What rectus nerve is not innervated by CNIII (oculomotor)?

Lateral rectus

What innervates the dorsal oblique?

Trochlear

What innervates the ventral oblique?

Oculomotor

What are the components of the eyelids?

Skin, cilia, SQ connective tissue, muscles, meibomian glands, conjunctiva

What are the functions of the eyelid?

Corneal protection

Produce, distribute tear film

What nerve causes the eye to blink?

Orbicularis oculi

What innervates the orbicularis oculi muscle?

CN VII

What elevates the upper eyelid?

Levator palpebrae superioris muscle

What innervates the levator palpebrae superioris muscle?

CN III

What muscle in the eyelid is smooth muscle?

Mueller’s

What is the function of the Mueller’s muscle?

Widens palpebral fissure, elevates upper eyelid and depresses lower eyelid

What eyelid muscle is nonfunctional with horners?

Mueller’s

What are the orbital glands?

Lacrimal

Gland of the 3rd eyelid

What orbital gland produces 60-70% of tear fluid?

Orbital lacrimal gland

Where is the gland of the 3rd eyelid located?

Base of the 3rd eyelid

What drains the tears?

Lacrimal puncta

What is a conjunctiva?

Mucus membrane

What are the conjunctiva?

Palpebral

Bulbar

Nicitans membrane

Conjunctival fornices

What conjunctiva lines inner surface of eyelids?

Palpebral

What conjunctiva covers the surface of the globe?

Bulbar

What are the tunic layers of the eye?

Fibrous

Vascular

Neural

What is in the fibrous tunic?

Cornea and sclera

What is in the vascular tunic?

Anterior uvea (iris and ciliary body)

Posterior uvea (choroid)

What is in the neural tunic?

Retina

What are the parts of the cornea?

Epithelium

Stroma

Descemet’s membrane

Endothelium

What innervates the cornea?

Pain receptors from ophthalmic branch of CN 5 superficially

Why are we able to see through the cornea?

No pigment or blood vessels

Non-myelinated nerve fibers

Relatively dehydrated

Arrangement of collagen fibers

What is the thickness of the cornea?

Less than 1mm

How long does it take for blood vessels to enter the cornea after injury?

3-5 days

Describe the corneal epithelium?

Nonkeratinized stratified squamous

Lipophilic

Barrier to drugs

What is required for a drug to enter the eye?

Hydrophilic and hydrophobic

Describe descemet’s membrane

BM of corneal endothelium

Lipophilic

Does not retian fluorescein

How many layers is the endothelium in the cornea?

1 layer

What is the regenerative ability of the endothelium in the cornea?

Poor

What part of the endothelium removes fluid from the stroma?

Na+/K+ ATPase pump

What are the parts of the sclera?

Limbus

Lamina cribosa

Where is the limbus?

Corneoscleral junction

What is the pigment of the sclera?

Variable

What is the lamina cribosa?

Location where optic nerve passes through sclera

What is the thickness of the sclera?

Variable but thinnest near the equator

What is in the anterior uvea?

Iris and ciliary body

What is in the posterior uvea?

Choroid and tapetum

What muscles are in the iris?

Iris sphincter muscle

Iris dilator muscle

What does parasympathetic stimulation do to the iris?

Makes it smaller

What does the sympathetic stimulus of the iris do?

Make it larger

What are the parts of the ciliary body?

Pars plicata

Pars plana

Zonules

Ciliary body muscle

What does the pars plicata do?

Produce aqueous humor by nonpigmented ciliary body epithelium

What do zonules do?

Attach ciliary body process to the equator of the lens

What part of the ciliary body does accommodation?

Ciliary body muscle

What is the conventional outflow pathway of aqueous humor?

1. Ciliary body epithelium

2. Posterior chamber

3. Pupil

4. Anterior chamber

5. Iridocorneal angle

6. Vortex veins

7. Systemic circulation

What is the unconventional aqueous humor outflow pathway?

1. Uveoscleropathway

2. Iris stroma

3. Ciliary body stroma

4. Supraciliary-suprachoroidal space

5. Sclera

6. Systemic circulation

What species has the most use of the unconventional aqueous humor outflow pathway?

Horse (50%)

What is in the posterior uvea?

Choroid

Blood vessels

Choriocapillaris

Tapetum

Large vessel layer

What is the main source of nutrition for outer layers of retina?

Choriocapillaris

What is the tapetum lucidum?

Reflective layer in the inner choroid in the dorsal fundus

What does the tapetum lucidum do?

Allow for second stimulation of photoreceptors

What animals do not have a tapetum lucidum?

Humans, red kangaroo, squirrels, llama, alpacas, and pigs

Where is the tapetum lucudum located?

Dorsal fundus

What do rods do?

Shapes and motion

What do cones do?

Color vision

What is the area centralis?

Area of high cone density

What animals have a fovea rich cone?

Avian, reptiles, and primates

What is the significance of the potential space between the retinal pigment epithelium and photoreceptors?

Retinal detachments occur there

Where is the retina attached very firmly?

Optic nerve head

Ora ciliaris retinae

What animals have a merangiotic pattern of the fundus?

Lagomorphs

What is a merangiotic pattern?

Blood vessels going lateral across the fundus

What species are paurangiotic?

Guinea pig, horse, elephant, wallaroo, tree kangaroo

What species have an anangiotic choroid?

Owl and flying fox

T/F you can see the optic nerve on a bird?

False

What is the most protein dense part of the body?

Lens

What are the parts of the lens?

Lens capsule

Anterior epithelium

Lens fibers

Equator

Nucleus

Cortex

What part of the lens capsule is larger?

Anterior side

What occupies 2/3 volume of the globe?

Vitreous humor

What is vitreous humor made of?

99% water, collagen, and hyaluronic acid

What are the functions of vitreous humor?

Transmit light

Maintain normal retinal position

T/F decussation of optic nerve fibers vary based on the species?

True