4: eyelids and lacrimal (copy)

eyelids and the lacrimal system

eyelids

the eyelids, or palpebrae are fold of skin and tissue that when closed cover the globe.

what are the 4 main functions of the eyelids

cover the globe for protection

move tears toward drainage at the medial canthus on closure

spread the tear film over the anterior surface of the eye on opening

contain structures that produce the tear film

on closure the upper eyelid moves down to cover the cornea

whats lagophthalmos 

refers to incomplete closure of the eyelids 

cause may be physiolgic , mechanical or paralytic 

tarsal section

first crease is top of cornea

palpebral fissure

area betwee the open eyelids.

upper lid just covers the superior limbus when one eyes are open

upper and lower eyelids meet at the corners of the palpebral fissure in the lateral and medial canthi

what is the floor of the lacrimal lake

the plica semilunaris 

this narrow screscent shaped fold of conjunctiva , located in medial canthus, allows lateral movement of the eye without stretching the bulbar conjunctiva 

carnucle

small pink mass of modified skin located just medial to the plica. covered with epithelium that contains goblet cells and fine hairs and their associated sweat and sebaceous gland

upper eyelid

extends to the eyebrow and is divided into the tarsal and the orbital parts

the tarsal portion

lies clostest to the lid margin, rests on the globe and contains tarsal plates

the skin i sthin and the underlying loose connective tissue is devoid of adipose tissue.

orbital portion

extends from the tarsus to the eyebrow , and a furrow- superior palpebral sulcus- separates the tarsal portion from the orbital portion 

This sulcus separates the pretarsal skin, which is tightly adherent to the underlying tissue, from the preseptal skin which is only loosely adherent to ts underlying tissue which contains a cushion of fat 

surafce anatomy of the right eyelid

inferior palpebral sulcus

in the lower eyelid, this seperates the lower lid into tarsal and orbital parts.

the tarsal portion rests against the globe and the orbital portion extends from the lower borde of the tarsus onto the cheek extending just past the inferior orbital margin to the nasojugal and malar sulci

eyelid margin

rests against the globe and contains the eyelashes and the pores of the meibomian glands, the clia (eyelashes) are arranged at the lid margin in a double or triple row 

lashes curl upwards and down on the lower lid 

eyelashes are richly supplied with nerves, causing them to be sensitive to the slightest touch , which we elicit a reflex - blink

abnormalities affecting cilia

various epithelial diseases can cause madarosis ( loss of lashes) or trichiasis (misdirected growth) in which the eyelashes grow toward rather than away from palpebral fissure. contact with the cornea can cause irritation anf painfl abrasions can lead to ulceration

epilation can remove the problem lashes

pores of meibomian glands

located posterior to the cilia, and the transition from skin to conjunctiva, the mucotaneous junction, occurs posterior to these openings

a groove called the gray line runs along the eyelid margin between the cilia insertions and the powers of the meibomian glands

this groove is the location of a surgical plane that divides the lid into anterior and posterior portions

eyelid margin divisions

2 parts:

the medial one sixth is the lacrimal portion and the lateral 5/6 is the ciliary portion,

division occurs at the lacrimal papilla

a small elevation containing the lacrimal punctum, the opening that carries the tears into the nasolacrimal drainage system

epicanthus 

vertical fold at the nasal canthus in the medial area of the upper eyelid and terminating in the nasal cathus area 

common in babies 

tarsal plate

toughest part - protective area of eyelid

made of connective tissue

protects from foreign bodies

covers the globe

cross section of middle of the eye

the tarsal meibomian glands are embedded in the tarsal plates. Their ducts empty onto the lid margins. they secrete lipid which forms part of the pre ocular rear film

superior lid the tarsal plate is bigger

meibomian gland

meibomian gland will several alveoli emptying into a single duct 

tarsal plate scan

runs all the way up

tarsal glands on the edge of the lid

glands exiting at the edge of the lids

in between the lashes and ocular surface and conjunctiva

when squeezed, the glands secrete oil

orbicularis muscle

the striated fibres of the orbicularis oculi muscle are located below the subcutaneous connective tissue layer and encircle the palpebral fissure from the eyelid magin to overlap onto the orbital margin, muscle divided into 2 regions- palpebral and orbital

palpebral portion

the palpebral portion of the orbicularis oculi muscle occupies the area of the eyelid that rests on the glod and is closest to the eylid margin

sometimes divided further into pretarsal and preseptal parts

composed of semi circles of muscle fibres that run from the medial orbital margin and the medial palpebral ligament to the lateral palpebral raphe

contraction of orbicularis assists in moving the tears through the canaliculi into nasolacrimal drainage system

also another muscle in this portion - riolan, lies near the lid margin on both sides of meibomian gland openings , it maintains lid margins close to the globe

ectropion

eversion of the eyelid margin. common cause of which is loss of muscle tone, a normal occurence in aging

lacrimal punctum no longer in position to drain tears from lacrimal lake

epiphora- an overflow of tears onto the cheek may occur

entropion

inversion of the lid margin may result from spasm of the orbicularis oculi muscle causing lid margin to turn inwards,

this puts th eyelashes in contact with the glob =e and can cause corneal abrasion

orbital portion of orbicularis oculi muscle

attached superiorly to the orbital margin medial to the supraorbital notch

fibres encircle the area outer to the palpebral portion and attach inferiorly to the orbital margin , medial to the infraorbital foramen

these centric fibres extend throughout the rest of the lid and over the orbital rim

orbicularis action

ring shaped muscle

orbic oculi is innervated byy cranial nerve VII

contraction of palpebral portion closes eyelid gently and the palepbra; orbicularis is the muscle of action in an involunatry blink and voluntary wink; relaxation of the levator muscle follows

the antagonist to the palpebral portion of the obicularis is the levator muscle 

the antagonist to the orbital portion is the frnotalis muscle 

when sphincters contract , palpebral aperture gets smaller 

spontaneous involuntary blinking

renews the precorneal tear film

reflex blink

protective and may be elicited by a number of stimuli- loud noise, cilial touch , conjunctival.

when orbital portion of orbicularis oculi contract the eye is closed tightly and the areas surrounding the lids- foreheadm teple cheek, are involved in contaction

this is a protective mechanism

forcing the eyelids are closed too tightly forces compressing the orbital contents can significantly increase intraocular pressure

superior palpebral levator muscle

is the retracctor of the upper eyelid

located within the orbit above the globe and extends into the upper eyelid.

originates on the lesser wing of the sphenoid bone aboove and infront of the optic foramen

superior transverse ligament- act as a fulcrum, changing the anteriposterior direction of the levator to superinferior.

picture shows saggital section of upper lid

superior transverse ligament

a fibrous band that spans the anterior superior orbit from the rochlea to the lacrimal gland fascia

provides support for the upper lid and orbital structures as well as acting a a fulcrum.

ligament is located at the point where the levator muscle fibres end and the aponeurosis begins

levator aponeurosis 

as it enters the eyelid, the levator becomes a fan shaped tendinous expansioin, the levator aponeurosis

spreads out into an extensive sheet posterior to the orbital septum.

fibres of aponeurosis penetrate the orbital septum and extend into upper lid 

these fibres pass through submuscular connective tissue ; posterior fibres insert into lower anterior surface of tarsal plate, anterior run between the muscle bundles of orbicularis to nsert into the skin of eyelid

this attachment of fibres from levator aponeurosis anchors the skin to underling tissues in pretarsal area of eyelid and creates the palpebral sulcus

what are the 2 side extensions of the aponeurosis

referred to as horns.

the lateral horn helps to support the lacrimal gland by holding it against the orbital roof , dividing the gland into orbital and palpebral lobes

lateral horn then attaches to the lateral palpebral ligament and lateral orbital tubercle

medial horn is attached to the medial palpebral ligament and medial orbital rim

orbital area viewed in front with skin, subcutaneous tissie and orbital septum removed

levator action (levator muscle ) superior

attached to the tarsal plate by aponerosis 

contraction of the levator muscle causes elevation of the eyelid

connection between the sheath of the levator and sheath of superior rectus coordinates eyelid position wih eye position so the eye is elevatedm lid is raised

levator muscle has to flatten out to be attached 

when the muscle contracts the tarsal plate is pulled back 

what is the levator muscle innervated by

innervated by the superior division of the oculomotor nerve, cranial nerve III

what 2 muscles open the superior lid

levator palpebrae superiosis

superior tarsal muscle

what muscle pulls down inferior lid 

inferior tarsal plate 

how are the eyelids closed

closed by the relaxation of the levator and contraction of theorbicularis oculi muscles. 

the tonic activity of the levator and relaxation of orbicularis oculi holds eyelid open. 

in a blink the tonic activity of the levator muscle is suspended , and bursts of activity the orbiculatis rapidly lowers the lid 

levator palpebrae superiosis muscle (levator muscke)

the muscle goes up and over the eyeball and attaches to the skull

sphenoid bone is where it attaches ot

tarsal muscle attaches to levator muscle

evator attaches to tarsal plate

retractor of the lower eyelid

capsulopalpebral fascia (lower eyelid aponeurosis )

an anteror extension from the sheath of inferior rectus muscle and suspensory ligament

inserts into the inferior edge of the tarsal plate

this insertion coordinates the lid position with globe movement

lower eyelid is depressed on globe depression and the lower eyelid elevates slightly on upwards movement of the globe

tarsal muscle (muller )

the superior tarsal muscle is composed of smooth muscle and originates from the postoinferior apect of the inferior muscle 

the smooth muscle fibres appear within the striated muscle at the point whch the muscle becomes aponeurootic 

supeiror tarsal inserts on the superior edge of tarsal plate 

contraction of the tarsal muscle can provide 2mm of additional lid elevation 

inferior tarsal muscle

found on lower eyelid

arises from inferior rectus sheath muscle and inserts into the lower conjunctiva and lower border of tarsal plate

both tarsal muscles are innervated by sympathetic fibres that widen the papebral fissue when activated

superior and inferor tarsal muscles

these are just underneath the levator muscle

smaller and smoother

attaches to levator muscle

tarsal plate 

each eyelid contains tarsal plate that gives the lid rigidity and structure and shapes it to the curvature of the globe 

palpebral ligaments

also known as tarsal ligaments

bands of dense connective tissue connecting the tarsal plates to the orbital rim and holding the tarsal plates in position against the globe during eye and lid movement

meibomian glands (tarsal glands )

sebaceous glands embedded in the tarsal plates

long multilobed glands resemble a large bunch of grapes and are arranged vertically such that their openings are located in a row o=along the lid margin posterior to cilia

in the upper and lower lid

secrete the outer lipid layer of the tear film

saggital section of the eyelid 

contact lens wear

loss of number of meibomian glands in cls

glands of zeis

secrete sebum into the hair folicle of the cilia coating the eyelash shaft to keep it from becoming brittle

glands of moll

modified sweat glands 

located near the lid margin anf their ducts empty into the hair folicle, into the zeis gland 

accessory lacrimal glands of krause

located in stroma of conjunctival fornix, and the accessory lacrimal glands of wolfring are located along orbital border of tarsal plate

glands are oval .

secretion contributes to the aqueous layer of the

more on orbicularis muscle

striated muscle along the lid margin small muscle bundles located on both sides of meibomian glands represent a specific part of orbiculairs, the ciliary part - riolans muscle,which holds the lid margin against the globe

attachments are nasal and temporal by tendons

medial- attached to maxillary process

temporally- zygomatic bone

orbital portion of orbicularis

lies in front of the bones forming the orbit

preseptal portion of orbicularis

lies in front of the orbital septum

pretarsal portion of orbicularis 

lies in front of the tarsal plate 

marginal / ciliary portion of orbicularis

closest to the lid margin

submuscular areolar layer

posterior to orbicularis

loose connective tissue

separates the muscle from the tarsal plate

between this layer and tarsal plate lies the pretarsal space

pretarsal space is between the orbicularis and orbital septum

where are the superor tarsal muscles located 

above the superior tarsal plate and insert into its upper edge 

what are the tarsal plates composed of

dense connective tissue

collagen fibrils of this tissue are uniform size and run vertically and horizontally to surround meibomian glands

what 2 layers are the palpebral conjuctiva composed of

stratfied epithelial layer and connective tissue stromal layer - submucosa

as conjunctiva lines the lid squamous l=cells are replaced by cuboidal and columnar cells forming a stratfied columnar mucoepithelial layer

this layer continues into the bulbar conjunctiva vecoming continous with corneal epithelium

whats the surface of superficial conjunctival cells and thei microvilli covered with

glycocalyx 

malanin granules found in cytoplasm of conjunctival epithelial cells near the limbus 

goblet cells

produce mucous component of the tear film located in epithelium of conjunctival

most dnense at the fornix 

subsurface vesicles fuse with epithelial cells increase adg=herence to tear film to the globe

goblet cells are scattered thoughout the stratofied columnar conjunctival epithelium

decrease with age and increases in inflammatory conditions as they produce mucin droplets that accumulate causing swelling in cells. surface cell thn ruptures releasing mucus

submucosa of the palpebral conjunctiva

thin in the tarsal portion of eyelid but gets thicker in orbital portion 

loose vascularised connective tissue subdivided into an oter lymphoid layer and deep fibrous layer 

immunoglobin A is in lymphoid layer making the conjucntiva an immunoglobically active tissue 

types of blink- reflex

quickest - fully open to fully closed tales 20-30 ms

subconcious

tightest

could damage the eye

reflex arc

signals dont go to the brain, it goes straight to the spinal cord

using facial motor nerve which innervates orbicularis muscle

types of blink - spontaneous bilnk

using tarsal portion of the orbicularis 

more slowly - 250 - 300 ms 

less tight

in response to any reflex or stimuli 

keeps the eye moist 

vary depending on age and environment 

if eye is super dry blink more, i

there to re new tear film 

purpose for spontaneous blink

tear film spreads on the blink

types of blink - voluntary blink

accompanied by an upward and outward movement of the actual eyeball beneath the lid ( bells phenomenon)

lower lid moves the most during this type of voluntary blink

orbtal septum 

barrier from the top of the tarsal plate up to the top of the orbit connextive tissue sheet 

barrier between orbital rim and fat and the lids 

keep stuff outsid the orbit

orbital fat provides padding behind the septum

orbital septum bigger than eyeball 

edge of eyelids

eyelashes

have glands of zeis and moll

secretes oily substances

these glands are associated with lashes- keeps them oily

lashes are for protection from debris

when the lashes are dry they struggle to portect from debris

so these glands secrete the oil

palpebral conjunctiva

dense vacular

regions of conjunctiva 

innervation of the eyelids 

the opthalmic and maxillary divisions of the trigeminal nerve provide sensory innervation of the eyelids 

upper is supplied by supraorbital , supra trochlear, infratrochlear and lacrimal nerves which are branches of opthalmic division 

supply to the lower lid

infratrochlear branch of opthalmic nerve and infraorbital nerve, a branch of the maxillary division

motor control of the orbicularis muscle

done through the temopral and zygomatic branches of facial nerve

motor control of levator muscle 

done through the superior division of the ocularmotor nerve 

the tarsal smooth muscles are innervated by the sympathetic fibres from superior cervical ganglion

blood supply to the eyelid

blood vessels located in a series of arcades or arches in each eyelid

marginal palpebral arcade lies near lid margin and peripheral near orbital edge of tarsal plate

these vessels are branches from the medial and lateral palpebral arteries

and the arteries are branches from the opthalmic and lacrimal arteries

normal variations occur in the blood supply and most common variation is a lack of peripheral arcade in lower eyelid

opthalmic and carotid - superior blood supply

lacrimal system

lacrial fluid ( tears) production - lacrimal gland and ducts

location is superior temporal region of the orbit

function is secretion of aqueous tears and their transport to the conjunctival fornix

lacrimal tear drainage- lacrimal sac and nasolacrimal duct

location is nasal inferior region of the orbit

function is drainage of tears from conjunctival sac into the nasal cavity

tear film functions

optically smooth surface covers the anterior surface of the globe 

keeps surface moist and serves as lubricant between globe and eyelids 

traps debris and helps remove sloughed epithelial cells and debris 

primary soruce of atmospheric oxygen for the cornea 

antibacterial function protects against infection 

flushing action revomes the cell debris and freign bodies 

helps with corneal wound healing - provides a pathway for WBC 

tear film layers

composed of 3 layers

lipid layer

aquous layer

mucous layer

lipid layer

outermost layer containing waxy esters, cholesterol and free fatty acids, primarily produced by the meibomian glands

the layer retards evaporation snd porvides lubrication for smooth eyelid movement

aqueous layer 

middle layer 

contains inorganic salts, glucose , urea enzymes portients glycoprotiens anf antibacterial substances.

it is secreted by the main and accessory lacrimal glands 

mucous layer

innermost layer

acts as an interface that facilitates adhesion of the aqueous layer of tears to the ocular surface

composed of the glycocalyx secretion from the surface epithelia and mucin produced and secreted by conjunctival goblet cells

mucins also bind and entrap bacteria and viruses blocking binding sites on microbes and preventing them from penetrating the ocular surface

1. base layer - mucus 

primary mucus secretion is by goblet cells of the conjunctiva, secondary secretion is by the lacrimal gland and non goblet cells in conjunctival epithelium 

function is to change tear dynamics:

helps viscosity when between blinks 

helps maintain a stable tear film 

low vsicosity in motion during blinks - aids tear film spreading 

function also is that mucin adheres to cell debris and foreign bodies, and hydrophobic cell membranes to allow aqueous to stick 

loss of mucus secretion increases tear film breal up and corneal dry spots 

poor mucin layer is shown on the right ,

dark areas are dry spots 

2. middle layer - aqueous 

produced by lacrimal gland

most of the tear film is porduced here

acessory lacrimal gland ( keause and wolfring) are in conjunctiva and have the same structure as the main lacrimal gland

aq layer protiens- defence mechanism:

immunoglobin A ,

lactoferin- combats infection and inflammation

lysozyme: antimicrobial agent

tear specific prealbumin (TSP)

lacrimal secretory system

includes main lacrimal glabd, the accessory lacimal glands, meiobiam gland and conjunctival goblet cells

where is main lacrimal gland located

located in a fossa on the temporal side of the orbital pplate of the frontal bone, posterior to the superior orbital margin

what does lacrimal gland consist of 

lobules made up of numerous acini. each acinus is an irregular arrangment of secretory cells around a central lumen surroundedby an incomplete layer of myopithelial cells. 

a network od ducts connects the acini and drains into one of the main excretory ducts 

where are accessory glands located

in the subconjunctival tissue from the fornix area to near tarsal plate. basic secretion maintains the normal volume of aq portion of tears

reflex secretion increases volume in response to a stimulus

what is lacrimal gland supplied by

lacrimal artery, a branch of the opthalmic artery

sensory inervation is through lacrimal nerve , a branch of opthalmic division of trigeminal nerve

glad recieves vasomotor sympathetic innervation ad secretomotor parasympathetic innervation

tear production and drainage 

tears produced supero tenporally through lacrimal ductsonto ocular surface 

the drained via canaliculi 

then entes punctum

goes then lacrimal sac and through naso lacrimal duct and into the nose 

lacrimal duct- goes from lacrimal gland to eye 

nasolacrimal duct- goes from eyeto the nose

main and accessory lacrimal glands

have superior and inferior accessory and main glands 

cross section of lacrimal gland

secretory granules helps create the aq layer

3. lipid layer

produced mainly from tarsal glands

makes lipid layer of tear film

primary lipid secretion is by tarsal glands and secondary secretion is by glads of zeis at the edge of eyelid

50 tarsal glands in upper 30 in lower

lipid secretion has a low melting point. forms a liquid at the temp of the ocular surface

lipid surface layer reduces evap of the aq tears

glands of the eyelid 

tear film distribution

lacrimal gland fluid is secreted into the lateral part of the upper fornix and descends across the anteriro surface of the globe

contraction of orbiculais forces meium out of the pores and lid motion can spread a thin lipic layer across the surface

each blink reforms the tear film spreading over ocular surface