Ocular A&P

Globe

Eyeball

Orbit

Bony structure where the globe sits

What does the orbit contain?

the globe, extra-ocular muscles, ligaments and tendons, connective tissue, part of the lacrimal gland, nerves, blood vessels, orbital fat

Ocular Adnexa

protective anatomical structures located adjacent to the eyeball

What does the ocular adnexa contain?

eyebrows, eyelashes, eyelids

• skin, muscles, lacrimal system, nerves, blood vessels

What are the 3 layers of the eyeball wall?

Fibrous Tunic, Vascular Tunic, Neural Tunic

What is found in the fibrous tunic

cornea, limbus, sclera

What is found in the vascular tunic

iris, pupil, ciliary body, choroid

What is the vascular tunic also known as

Uvea

What the inner most layer of the eyeball wall

neural tunic

What is another name for the neural tunic

retina

What is found in the neural tunic?

neural (sensory) layer

retinal pigment epithelium

What is the outer fibrous tunic purpose

protective and structural

Cornea

transparent dome, allows light rays to enter the globe, brings light rays into focus on the retina

Limbus

transition zone between the cornea and sclera

What is the function of the limbus?

contains stem cells and structures that drain fluid

Sclera

Opaque, takes up majority of the outer layer, 5/6 coats

What is the purpose of the sclera

structural support

What do both the sclera and cornea have in common

both are made of collagen fibers and are continuous

The sclera is uniform or non-uniform collagen

non-uniform

The cornea is uniform or non-uniform collagen

uniform

The vascular tunic is also known as

uvea

What is function of the uvea

majority of the eye blood vessels and melanin pigment

Iris

colored part of the eye, houses the pupil, controls light entry by adjusting pupil size

what iris muscle is responsible for constricting the pupil?

iris shpincter

What iris muscle is responsible for dilating the pupil?

iris dilator muscle

How is eye color determined

the amount of melanin pigment

Ciliary Body Functions

fluid motion, Accomodation

Pars Plicata

highly vascular folds, “ fingers” produce fluid

Does the muscular portion involved in accommodation occur in the pars plicata or the pars plana

pars plicata

Pars plana

thin, pincushion of the eye - not much vasculature

What does the ciliary body look like?

a small brown band located right outside of the iris

Where are injections typically done?

Pars plana

Choroid

mostly blood vessels and melanin pigment, absorbs scattered light, metabolic support to overlying half of the retina

What are the two components of the ciliary body

Pars Plicata and Pars Plana

What is the main purpose of the neural (sensory) retina?

convert photons of light into chemical and electrical signals, then send the signals down the optic never to the brain for processing

What portion of the retina takes up the most layers?

Neural Retina

What portion of the retina only takes up 1 layer?

Retinal Pigment Epithelium

What is the function of the retinal pigment epithelium?

assists in nourishing the outer retina

What are the three fluid like chambers (in order from front of eye to the back)

Anterior Chamber, Posterior Chamber, Vitreous Chamber

What is the purpose of the anterior chamber?

Space from the back of the cornea to the front of the iris

What forms the anterior chamber angle?

iris and cornea

what is the posterior chamber’s purpose

houses the lens

What does the posterior chamber look like?

donut shaped right behind the iris

What is the largest chamber?

vitreous chamber

Where is the vitreous chamber?

behind the lens

What is the is the aqueous humor?

the clear watery fluid

Where is aqueous humor located?

BOTH anterior and posterior chamber

Is the aqueous humor continuously produced and drained?

yes

What are the steps in the process of aqueous humor drainage?

produced in the posterior chamber from ciliary bodies, flows through the pupil into the anterior chamber, then drained out of the anterior chamber angle

What is vitreous humor?

clear, gel-like fluid (think egg whites)

Where does the vitreous humor fill?

vitreous chamber (space between the lens and retina)

Is vitreous humor continuously produced or drained?

No

Do you have the same vitreous humor your entire life?

yes, it is formed during embryonic development

What fibers control the lens shape to see at variable distances?

zoluna fibers

Do the superior or inferior zoluna fibers cause slack?

superior

Do superior or inferior fibers cause tense

inferior

What is the lens held in place by?

zonules that attach to ciliary body

What is the function of the lens?

Contributes 1/3 of the refractive power (helps focus light rays on the retina)

How does the lens adjust to see at different distances?

The contraction of ciliary muscles in the ciliary body causes the zonules to be more flaccid, so the lens can change shape

Is the eyeball a perfect sphere?

No, the cornea has a steeper curvature

What is the average anteroposterior diameter in adults?

24 mm (23-25)

What is the radius of the cornea

about 8 mm

what is the radius of the sclera

about 12mm

What is more pointy the sclera or cornea?

the cornea

What is most refractive error due to?

large or small axial lengths

Clinically for every 1 mm of change in the axial length from 24 mm, there is a shift in how many diopters?

3.00

Hyperopia

shorter axial length, farsighted

emmetropia

average axial length

myopia

longer than average axial length, nearsighted

What are the poles of the eye?

Anterior and Posterior poles

Where is the anterior pole

tip of the cornea (apex)

Where is the posterior pole?

point directly opposite the anterior pole

Is the optic nerve nasally or temporally displaced

nasally

is the temporal or nasal side longer?

temporal

In anatomical position, where are the eyes?

in the primary position of gaze

Anterior or ventral

towards the front

posterior or dorsal

toward the back

with the globe, everything located closer than the cornea is considered what?

anterior

Anything behind the cornea in the globe is what?

posterior

Superior or cranial

toward the head, above

inferior or caudal

away from head or below

medial or nasal

towards the mid line/nose

lateral or temporal

towards the temple or away from the midline

Proximal

closer to the point of attachment of limb to the body

Distal

farther from the point of attachment of a limb to the body trunk

Inner

closer to the center or vitreous

Outer

lies farther from the vitreous

sagittal

in half vertically

coronal or frontal

in half horizontally (separating the front from the back)

transverse or cross or axial

top and bottom half split in two

meridonal

diagonal

Eyebrows

thick skin with cilia, does have fat pad underneath

Glabella

smooth space between the eyebrows

What are the functions of the eyebrows

mainly protection, facial expression

What muscles produce eyebrow movements?

frontalis, corrugator superciliaris, procerus, obricularis oculi

Frontalis muscle orgin

high on the scalp

What does the frontalis muscle do?

the main eyebrow raiser

Procerus muscle action

creates horizontal lines on the bridge of the nose

What is the look that uses the procerus muscle

the menace, or its smells look