lids and conjuctiva Flashcards
what are the functions of the eyelids
- protection - light entering the eye , direct trauma , air particles ( e.g. blinking reflex)
- lubrication - distributes tear film , provides comfort , removes debris
- globe position - maintains position in the orbit (with conjuctiva)
what is the top part of the eyelid called just below your eyebrow
- orbital portion
what is the palperbal sulci
- palpebral - refers to the eyelids themselves
sulci- refers to folds
- therefore palpebral sulci = eyelid fold
- the reason you have this fold is because you have a structure called the tarsus - the tarsus is a connective tissue band that inserts into the eyelid- because of the tarsus and its insertion point it creates a groove in your eyelid
what is the tarsus portion of the eye
- the tarsus is the actual upper eyelid and the palpberal sulci is the fold it creates
what is the open bit of the eyes
-the open bits of the eyes = the palpebral aperture - (the open bits of your eyes)
important in condition called ptosis- when your eyelid is not fully open - you have decreased palpebral appeture - this can be measured clinically in mm - and this gives yoiu an indication of the severity of the ptosis- it would obstruct the vision and this patient would most likely need surgery to lift the eyelid up
where is the medial canthus and lateral canthus
medial = closer to the nose
canthus = thick connective tissue bands where your muscles around your eyelids attach to
medial and lateral canthus = inner and outer parts of your eyes
- if a patient has had a traumatic injury and they are bleeding behind the eye
- if there is a lot of blood trying to push forward in a tight space- it will place a lot of pressure on the optic nerve- if that happens for too long the optic nerve will become damaged leading to blindness-
what is lacus lacrimalis
- lacus lacrimalis - translates to lake of tears- the pink inner part of your eye
what are the layers of the eyelid
skin
subcuntaneous tissue (very little fat)
obicularis oculi - involved in eyelid closure - innerveated by the facial nerve
orbital septum and tarsus - orbital septum seperates the eyelids- between eye lid and opitice nerve - infection of the eyelids before the optic septum = pre- septal cellulitis - cellulitis is an infection of the skin - in front of the eyelids - the eye itself is not affected it is protected by the septum - if it goes beyond the septum the infection can spread directly into the brain and can be fatal this = septal cellulitis
levator palpebral superioris - innervated by oculomotor nerve - elevates the upper lid ( only in upper lid) - you have a smooth muscle attached to the lps - also helps to lift the lps - sympathetuically innervated( not innervated by cnIII)
smooth muscle
conjuctiva
what is the difference between preseptal and septal cellulitis
- preseptal- only the eyelids are affected - no visual symptons
- septal cellulitis - after the orbital septum - most common cause = infection from one of the sinuses- usually from the maxillary sinus
where is the obiclularis oculi located and what is it responsible for
- the obicularis oculi is responsible for lid closure and surrounds the upper and lower lid and is innervated by the facial nerve
-
what are meibomian glands
- meibomian glands- glands that produce an oil which covers the tear film
the top layer of your tear is formed by the meibnomian glands- which is a lipid which is fatty tissue- it prevents the tears from evaporating - it keeps the eye moist- otherwise all your tears would evaporate and your eye would become dry very quickly
how is the eyelid seperated
- lid is seperated into anterior and posterior lamellae by the grey line
- anterior lamellae- composed of the skin and obicularis oculi muscle
- posterior lamellae - tarsus and conjuctiva
describe the structure of the obicularis oculi muscle
- concentric bands of striated muscle- surrounds the eye itself - both the upper and lower lid
- innervated by facial nerve -cranial nerve vII
- involounatry blinking , volountary closing , tear drainage
- seperated into orbital , palpebral , lacrimal
- palpebral portion subdivided into preseptal and pre tarsal
- medial and lateral canthal tendons strongly attached to the obicualaris oculi
what are the functions of the different parts of the obicularis oculi
- orbital portion - acts like a purse sting to strongly close the eyes - e.g. in bright light - not responsible for blinking - around the orbit itself- if you ask a patient to close their eyes very tightly- it is the orbital part that you are contracting -
- palperbal portion - volountary and involountary closure of the lifs (e..g blinking and sleep) -
- lacrimal portion
draw lids and lacrimal papillae medialhy , dilate lacrimal sac during blinking- when your obicularis oculi muscle contracts it makes it easier for your eye muscles to go down the tear ducts to get away from the eye
when your blinking what part of the obicularis oculi is contracting
- the palpebral portion
what part of the eye is responsible for volountary closure of the eye
- the orbital portion
at the lid margin what are the small muscle fibres calle d
- at the lid margin there is a small group of very fine muscle fibres called the cillary muscle or muscle of rolan
what is the orbital septum
seperates the eyelids from the eye itself
extension of the periosteum - (layer of thick firbous tissue that covers bones ) from orbital roof and orbital floor
seperates the lids from the orbit - clinically signifcant pre- septal vs orbital cellulitis
- seperates anterior and posterior lamellae
where does the lps origintate from
- originates in the lesser wing of the sphenoid
- inserts into upper lid skin via apeneurosis
- eleavates and retracts upper lid- inserts directly into the skin of the eye-
at superior transverse ligment forms aponeurosis
superior division of cn III
- Supplied by opthalmic and supraorbital arteries
describe the structure of the superior tarsus muscle
- smooth muscle which originates from the levator muscle itself at the level of whitnalls ligment - and is innervated by your sympathetic system - also called mullers muscles
- also helps to elevate the eyelid
- inserts into tarsal plate
- elevates upper lid
- smooth msucle
- symoathetic innervation
inferior tarsal muscle is analogous in lower lid——
what are tarsal plates
- part of your orbital septum
- modified thickening of septum, provides rigidity
- contains meibomian glands- produce lipid layer which covers your tear film which open at the lid margin
upper tarsal plate = 10mm , lower tarsal plate= 5mm (with fewer glands)
- skin moves freely over anterior surface , conjuctiva is densely adherent to the posterior surface
- from the medial and canthal ligaments which attach to maxilla and zygoma respectivley
describe the structure of the lid margin
30mm x 2mm
seperated into 2 sections by lacrimal punta
lateral 5/6 square edged
medial 1/6 round - edged without lashes
what does the anterior lamellae contain
- skin and obicularis oculi muscle
posterior lamellae
- posterior lamellae contains the tarsal plate and the conjuctiva
what are meiobmian glands
- type of sebaceous gland in the tarsal plate
- 30 in the upper lid , fewer in the lower lid
- secreate meibum
- prevents evaporation of aqueous tear film
what is it called when the meibomian gland is blocked
- chalazion
- lid lump that occurs when your meiobmian glands are blocked and the lipid as nowhere to go
- a stye occurs when the eyelash hair follcile is infected
what are the glands of moll and the glands of ziess
glands of moll
modifed apacrine sweat glands that help to keep lashes supple
glands of zies
sebaceous glands to lash follicles also maintain quality of lashes
where does the orbital septum lie and what is its function
- the orbital septum seperates the lid from the orbit
- this is an extremely important distinction clinically (orbital infections can spread to the brain and prove fatal)
describe the LPS
- the LPS is responsible for lid elevation and is innervated by cn iii this is aided by the superior tarsus muscle , which is a smooth muscle innervated by the sympathetic system
describe meibomian glands
- open on to the lid margins and secreate lipids which form the most superficial tear film layer,, preventing evaporation. blockage of these glands leads to a chalazion
what is the obicularis oculi responsible for
- obicularis oculi is responsible for lid closure
- innervated by cn 7 the facial nerve
- orbital portion involved in tight closure of the eyelids
- palpebral portion involved in light closure of the eyelids
what is the afferent pathway and effector muscle in the corneal reflex
- afferent pathway= sensory ending in corneal endotheium - long xillary nerves nascoiallry nerve which is a branch of the opthalmic division of the trigeminal nerve
- effector muscle - obicularis oculi
how is blinking innervated
- autonomic control
- variable frquency and speed
- no clear stimulus
what is a ectropian
when your eyelids are moving away from the eye
different reasons for a ectropian
- involutional - age related
- paralytic - if the muscles are not working correctly to keep the lid in position
- circratial- if their is a scar in your lower lid- that is pulling the eyelid down this can lead to a ectropian
- mechanical- if their is any sort of swelling that is physcially pushing the eyelid down
- congneital - born with an ectropian
- tears are unable to drain properly causing tear film insufficeny, dryness and pain
- becuase your lids are not effectivley spreading the tears over your eyes you can end up with eye dryness - when you have eye dryness- this is painful because your cornea is heavily innervated
- tears are unable to reach the punctum- eyes are watery
what is an entropian
- when your eyelids turn inwards
- causes
- involoutional - age related
spastic
- cicatricial - scarring process-
congential
eyelashes begin to rub against the eye causing a foreign body sensation , irritation redness, may damage the cornea- bevcause eylashes are consantly rubbing against the cornea.
what blood vessels are your eyes supplied by
pretarsal- supericial temporal and facial arteries - branches of external carotid artery
post - tarsal - branches of opthalmic arteries (branch of the ica)
venous
- medial part - opthalmic and angular veins
lateral part - superficial temporal veins
what is lid eversion
ectropian - and this can cause a watery eye due to the tears not draining via the punctum
what is lid inversion
- entropian - and this can lead to corneal damage due to the lashes irratating the cornea
where do the lids recieve their blood supply from
the lids recieve their blood supply from both the internal and external carotid arteries which anastomose
describe the venous drainage of the eyelids
- submandibular nodes from the medial aspect of the lids and via the preaurciualr nodes from the lateral aspect
how do the upper lids recieve their innervation from
- the upper lids recieve innervation via cn v1, whilst the lower lid recievs innervation from both cn v1 ( medially) and v2 laterally
where does the medial aspect drain into
medial aspect to submandibular nodes and lateral aspect to preauricular nodes
what nerves are the upper and lower lids innervated by
upper lid - v1
lower lid - v1- medial part
lower lid - v2- lateral part ( maxiallry divison)
what is the opening of the eyelids called
- the eyelids are spilt into upper and lower portions which meet at the medial and lateral canthi of the eye
- opening of the two eyelids = palpebral appeture
what are the layers of the eyelids
- skin and subcuntaneous tissue
- orbicularis oculi
- tarsal plate
- levator apparatus
- conjuctiva
what are the three parts of the obicularis oculi
- palpebral part - gently closes the eyelids
- lacrimal part- involved in drainage of the tears
- orbital part - tightly closes the eyelids
innervated by the facial nerve
where to the meibomian glands lie
the tarsal plates lie in the meibomian glands
what is the conjuctiva
- lies on top of the sclera
- thin , translucent membrane
- attaches globe to the lids
- erpithelium continous from the mucocutaneous junction - all the way to the corneal limbus =
describe the functions of the conjuctiva
-lubrication
contributes to muscous part of the tear film
- recduces friction
allows free movement of the lids
immune defense
- contributes to protection of the eye
describe the anatomy of the conjuctiva
- palpebral (relating to lids )conjuctiva - adherent to the tarsal plate- tighlty bound to the posterior eyelid- that is where the conjucitva starts
- forneicel conjctiva - contains some lacrimal glands
- bulbar - relating to eye globe - conjuctiva - oerlies anterior globe and eoms
describe the structure of the
Caruncular lacrimalis
pink bit of eye (medial aspect)
- modified skin with volumes of acessory lacrimal - help with tear formation and sebaceous glands - prevents evaporation of tear film layer
-
describe the structure of the plica semilunaris
- plica semilunaris
- fold of conjuctiva rich in goblet cells and immune cells , may faciliatate lateral movement
describe the conjuctiva histology
- epitheloum vairies by location
- palpebral part = non keratanised stratfied squamous
- stratifies coloumunar on bulbar part
what type of cells are in the conjuctiva
goblet cells
- unicellular
most in fornicies and pilica semilunaris
produce majority of conjuctivival mucins
immune cells
- langerhan cells help prims immune response (antigen presenting)
- lymphocytes
melanocytes
- varies depending on race
descirbe the blood supply of the conjuctiva -
- rich vascular netwoek within stroma
similar to the lids
additionally some supply from the anterior cillary arteries
describe the sensory innervation to the conjuctiva
- palpebral part - mostly from v1- opthalmic divison of the trigeminal nerve
inferomedial fornix and palpebral part - cn v2
- bulbar
long cillary nerves
what glands do you have in your conjuctiva
acessory lacrimal glands - glands of krause - found in superior fornix
glands of wolfring - found in superior tarsus
mucus secreating glands - glands of henle- scattered throughout the conjuctiva
what is the effect of a cn III palsy on the lid
- the levator palpebrae superioris is innervated by the cn 111
- LPS elevates the eyelid- therefore you would have ptosis
- in a surgical third nerve palsy - i.e. something that needs to be surgially managed i.e. a tumour or something that is compressing on the third nerve- if you have a surgical third nerve palsy that is exernally compressing the third nerve - parasympthatetic fibres lie outside the third nerve so if you have something compressing it from the outside- the parasympathetic fibres are affected which also effects your pupils so in a third nerve palsy involving the pupil you are more worried that something is pressing on the nerve from the outide- that is called a surgical third nerve palsy
a medical third nerve palsy - e.g. diabetes or hypertension it will most likely affect the blood supply which is on the inside of the nerve and spares the parasympathetic supply so the pupils are not involved
which muscle is affected by the disruption of the sympathetic chain
- smooth muscle- innervated by the sympathetic system (mullers muscle) which is on the lps- mullers muscle helps with lid elevation
- if you have a disruption in the sympathetic chain- you would except to see ptosis but would not be as severe as the one you would have on the lps
- this is called a partial ptosis
the sympathetic system also dilates the pupil - so if you have a problem with the sympathetic chain on examination you may see small pupil and ptosis
what condiiton is it when you have a disruption in your sympathetic chain
- horners syndrome - you would see a small pupil with a partial ptosis
why eyelid muscle is innervated by cranial nerve 7
- obicularis oculi
- involved in eyelid closure
if cranial nerve 7 is not working properly you are unable to close the eye - this can lead to corneal damage and a dry eye
- you can end up with corneal scarring
graves disease leads to proctosis because you have swelling of the eom muscles that can lead to exposure keratopothy ( corneal damage due to exposure to the enviroment)
which of the following was most likely to be seen in a patient with a cn 111 palsy
cn 3 palsy - symptons = ptosis, pupil dilation
what might the diagnosis for a patient who is unable to close their eyes be
- cranial nerve 7 palsy - facial nerve - obicularis oculi muscle is unable to close the eye properly -
- horners syndrome = disruption of the sympathetic pathway
- a cranial nerve 7 with no obvious cause = bells palsy
what is bells phenemonon -
bells phenomena - globe turns upwards upon eye closure
what are the functions of cranial nerve 3 regrarding the lids and how does a crnail nerve 3 palsy damage the eyes
- superior division of cn III innervates the levator palpebrae superioris muscle
- palsy therefore leads to failure of lid elevation - leading to ptosis
- you also lose innervation to superior rectus , medial rectus, inferior rectus and inferior oblique
what happens to the eye if you have a cn 7 palsy
cn vII innervates the obicularis oculi muscle
- palsy therefore leads to failure of eye closure = lagopthalmos (incomplete eye closure)
- cn 7 also innervates the rest of your face e.g. forhead muscles , mouth muscles all of the muscles of facial expression
how can CN VII palsy lead to blindness
- incomplete closure (lagothalmos) of the eyelids leaves the cornea exposed and dry
- this increases the risk of exposure keratopathy and subsequent ulceration , infection and scarring with eventual blindness
-
how can you prevent a cn 7 palsy causing blindness to exposure keratopathy
- preventitive measures include
- regular lubricant drops and ointments
eyelid taping
tempoary tarsorrhapy (suturing the eyelids shut)
- permeant tarsorrrhaphy
why does a umn lesion spare the forehead
-the part of your facial nerve which innervates your forehead muscles- they recieve innervation bilaterally- you have a bilateral upper motor component to the upper face- to the forhead muscle - this is called bilateral cortical representation
anything that is in your brain and spinal is upper motor neurone
once it leaves the spinal cord at the level of the spinal cord that = lower motor neurone
forhead muscle input has bilateral coritcal representation which impiles that a umn lesion will be compensated by the contralateral umn fibres thus sparing the forhead
- lmn lesions affect the entire half of the face
what is horners syndrome and the consequences
disruption in sympathetic chain
- affected structure
- mullers muscle
- dilator pupillae
- sweat glands
classic traid of
misosis - pupil dilation
partial ptosis (since levator is still working)
ipsilateral anyhydrosis (unable to sweat on the half of the face that is affected)
horners syndrome by itself is not a diagnosis because it can be caused by a multitude of things
