Ocular Anatomy 1

where does the equator of the eye lie

runs in the coronal plane

what does the orbital fascia envelope?

the structures of the orbit

what is the orbital fascia and what does it do?

thin, dense connective tissue, that wraps around everything and supports/protects muscles/eyes/bones etc

what is the difference between the periorbita and the periosteum?

periorbita lines the bones of the orbit, periosteum lines bones NOT in the orbit

Frontalis muscle

origin: scalp

insertion: superior orbital rim

function: raise the eyebrow

innervated by CN 7 (temporal branch)

which way are muscles pulled?

pulling insertion towards origin

procerus

origin: nasal bone

insertion: medial side of frontalis

function: pulls medial brow inferiorly

innervated by CN 7 temporal

corrugator supercilii

origin: frontal bone (inferior medial aspect)

insertion: skin superior to medial eyebrow

function: moves brow medially

innervated by CN 7 temporal

depressor supercilii

origin: maxilla bone (superior medial)

insertion: dermis under medial bone

function: depress the medial brow

innervated by CN 7

orbicularis occuli

origin: medial bony orbit

innervated by CN 7 (temporal, zygomatic, and buckle branch)

function: closes eyelid gently, depresses brow

where are the muscles of the glabellar region

space between eyebrows

what is the purpose of eyebrows?

nonverbal communication, protection against dust/debris, evaporative heat loss/thermoregulation, protection if we get hit in the face, shade from the sun

another name for eyelids and their purpose

palpebrae; protects globe of eye, moves and spreads tears, produces tear film

what is lagophthalmos and what might it result in?

incomplete closure of eyes; can result in improper tear drainage, corneal ulceration, inflammation

what might cause lagophthalmos ?

scarring, thyroid disease, tumor, blepharoplasty etc

tarsal vs orbital portions of eyelid

tarsal: skin tightly adhered to underlying tissues (reduces friction as it moves across eye)

orbital: skin loosely adhered to underlying tissues (contains fat, is squishy)

what separates the tarsal and orbital portions?

superior and inferior palpebral sulcii (grooves)

what is the palpebral fissure?

the space between open eyelids

what are the 2 structures the medial canthus contains?

plica semilunaris (pleat on eye surface) and caruncle (small mass of skin in inner corner)

what are the functions of the lacrimal papilla and puncta?

nasal drainage

what are the 2 parts of lid margin the lacrimal papilla separates into?

lateral ciliary portion (eyelashes) and nasal lacrimal portion (puncta, plica, and caruncle)

what is the epicanthus?

fold of skin that covers caruncle and plica semilunaris; usually found in asians and young children (disappears by birth usually), and ppl w developmental differences

what are some clinical considerations regarding the cilia?

madarosis: loss of eyelashes (or brows)

poliosis: whitening of the cilia

trichiasis: misdirected growth of eyelashes

what are the pores of the meibomian gland?

pores that are embedded in eyelid, they secrete oil from glands

what part of the eyelid are the pores of the meibomian gland found?

ciliary portion

what is the grey line?

a furrow between the cilia and the meibomian pores

what is blepharospasm?

spasmodic contraction of the orbicularis oculi muscle in response to pain/irritation

orbital portion of orbicularis oculi

origin: medial bony orbit

insertion: multiple bones and fascia areas

action: closes eye tightly

opposing muscle: frontalis

palpebral portion of orbicularis oculi:

contains medial and lateral palpebral ligaments

origin: medial palpebral ligament

insertion: lateral palpebral ligament

action: closing eye gently, involuntary blinking

what is the difference in the functions of the palpebral and orbital portions of the orbicularis oculi?

orbital uses more force when closing eyes, palpebral is gentler, used more for everyday

what is the muscle opposing the palpebral orbicularis oculi?

levator palpebrae

what are 2 specific muscle areas of palpebral orbicularis oculi?

Horner’s and Riolan’s

Horner’s muscle

Pars lacrimalis; encircles canaliculi;

action: compresses canaliculi and helps push tears in a specific direction/drains tears

how often is horner’s muscle activated?

every time you close your eyes, helps moves tears off ocular surface

Riolan’s muscle

pars ciliaris, located around meibomian gland, posterior to cilia

action: holds eyelid margin in close contact with globe of eyeball

(loss of muscle w/ age causes lid to sag and pull away from eye)

what are some clinical considerations of Riolan’s muscle?

entropion - inversion of lid margin (lid margin is pulled inwards toward ocular surface)

ectropion - eversion of lid margin (lid margin pulls away from ocular surface)

epiphora - overflow of tears (could be due to allergies etc)

How does Riolan’s help with tear film production?

It pushes on the meibomian gland to secrete oils to help with tear film production

What is Riolan’s seen as clinically

the grey line

levator palpebrae (superior palpebral levator/LPS)

Found in superior eyelid; striated muscle

origin: back of the orbit attaching to fascia of sphenoid bone

insertion: fibers pass perpendicular to orbicularis to insert in skin and tarsal plate

action: elevates eyelids

innervation: CN 3 (oculomotor, superior branch)

levator aponeurosis

levator inserts in a fan shape at the front of the tarsal plate

how do the superior palpebral levator and lacrimal gland interact?

the LPS divides it into 2 lobes, orbital lobe attaches closer to the orbital bone, the palpebral lobe attaches closer to the palpabrae. this helps keep the lacrimal gland in place against gravity

what are the expansions of the levator aponeurosis called?

medial and lateral horns

where does the medial horn attach?

near the fronto-lacrimal suture and medial palpebral ligament

where does the lateral horn attach?

the zygomatic bone (specifically orbital tubercle) and lateral palpebral ligament

what is ptosis and when might it occur?

lid droop; could occur when you have loss of tone of the levator

Muller’s Muscle (superior tarsal muscle)

non-striated

origin: levator (posterior)

insertion: superior margin of tarsal plate

innervation: sympathetic system

action: additional lid elevation (widens palp. fissure by a few cm)

inferior tarsal muscle

origin: inferior extraocular muscle sheath

insertion: lower conjunctiva and inferior border of lower tarsal plate

innervated by sympathetic system

actions: widens palpebral fissure (pulls lower lid down)

what makes the inferior aponeurosis different from the levator aponeurosis?

inferior aponeurosis is connective tissue, NOT muscle

inferior aponeurosis

origin: expansion of the inferior extraocular muscle sheaths

insertion: anterior and inferior tarsal plate and skin of eyelid

action: lower lid elevation/depression

submuscular areolar layer

anterior to tarsal plate, and posterior to orbicularis oculi; levator aponeurosis runs through it

tarsal plates (Tarsus)

crescent-shaped dense connective tissue

function: conforms lid to shape of globe

superior tarsal plate is larger than inferior tarsal plate

borders of tarsal plate?

orbital border: attached to orbital septum

marginal border: at lid margin

sides: attached to bony orbital margin by palpebral ligaments

palpebral conjunctiva

lines posterior aspect of eyelid

composed of an overlying epithelium and an underlying stroma, contains goblet cells

what is the junction where conjunctiva turns into skin? is it continuous?

mesocutaneous junction, continuous

what is the difference in epithelia between skin and conjunctiva?

conjunctiva is non-keratinized and wetted, skin is keratinized

where are the meibomian glands found?

tarsal plate

which lid has more MGs?

upper lid

what shape are meibomian glands?

long, brancing acini

what do MGs produce and what type of land are they?

sebum/meibum, holocrine gland

chalazion

clogged meibomian gland with/without inflammation (non-infectious)

meibomian dysfunction

thickened lipid secretion, keratinization of the duct, reduction in lipid content of tear film (abnormal secretions)

Zeis glands

histologically same as meibomian, sebaceous gland, lubricates eyelashes and protects

Glands of Moll

Serous glands, apocrine gland, involved in the immune response, located in eyelid margin

Hordeolum

acute inflammation of an eyelid gland due to infection (staph)

what is an external hordeolum?

stye, caused by infected zeis/moll gland (more anterior/external)

internal hordeolum

infected meibomian gland (more posterior)

accessory lacrimal glands

glands of krause - orbital-most aspect of eyelid, more in upper lid

glands of wolfring - edge of tarsal plate, more in upper lid

do we have more glands of krause or wolfring?

glands of krause

orbital septum (septum orbitale/palpebral fascia)

thin connective tissue associated with the eyelids

what is the function of the orbital septum?

creates barrier separating lid and orbit

where does the orbital septum attach?

Tarsal plate and periorbita, fuses with aponeurosis (in superior and inferior lids)

where does the orbital septum lie in regards to the medial/lateral palpebral ligaments?

In front of lateral palpebral ligament, behind medial palpebral ligament

what is the function of the orbital septum?

it protects the structures of the orbit from the outside structures