eyelids

why do we have eyelid?

protecction = closure ( blink reflex for light/trauma)

turnover of precorneal tear film and remove debris

lash prevent dust and sweat to enter eye

= distribute and maintain uniform surface of tears

gross anatomy of upper eyelid

from eyebrow to superior boundary of palpebral fissure

large mobile

gross anatomy of upper eyelid

inferior boundary of palpebral fissure to merge into cheeks

in primary position what location are the eyelids

upper eyelid 1/6 cornea

lower lid just covers inferior cornea/limbus

what are the palpebral sulcus

there is 2 , superior and inferior palpebral sulcus

seperate orbital and tarsal sections

inferior sulcus is less defined

describe the superior lid crease ethnic variations? particularly in south east asians

superior lid crease tends to be 8-12mm above upper lid margin

in south east asians, superor crease is 2-5mm above upper lid margin

orbital septum and tendon fuse at lower level

alllows less fat to occupy position more inferior and anterior

what is the palpebral fissure

the space between upper and lower lid margins

at birth 20mm width and 8mm height.

in adults , 30mm width and 10mm height

in 50% people lateral canthus is around 2mm higher than medial canthus

south east asians hae lateral canthus aroybd 5mm higher than medial

what is ptosis

droopy lids

reduced palpebral fissure

what is the canthus

two eyelids meeting place

inner ( medial) and outer (lateral) canthi

what is the caruncle

modified skin containing sebaceus glands and hairs ( pink and raised)

what is the plicasemilunaris

highly vascular

crescent shaped fold of conjunctiva

lateral of caruncle

similar to nicitating membrane (3rd eyelid of animals)

what are the eyelid margins

2mm in width, 30mm long

each divided into 2 parts

anterior outer aspect (cilia)

posterior inner aspect ( glands)

2 zones seperated by internal change in histological structure = grey line

why are lid margins so important?

They play a critical role in protecting the eye, maintaining moisture, and contributing to tear film stability.

describe the lashses or cilia in the eyelids

cilia have 2-3 rows

highly sensitive to touch

differentiated glands open into each hair follicle (e.g. sebaceous, sweat glands)

upper eyelid = 100 - 150 cilia - longer curve upward

lower eyelid = 50-75 cilia, curve downward

describe the human eyelash growth cycle

grow to full length in months

last another month then shed

prone to recurrent infection ( open access site)

may see excessive lash loss or lash discoloration with eyelid disease

what is madarosis

abnormal lash loss

what is the gland of zeiss

modified sebaceous gland

associated w eyelash follicles,

oily secretion

lubricate lid margin

prevent tear overflow and evapoation

what is gland of moll

modified sweat gland

open into lash follicle or directly into anterior margin between lashes

what happens when gland of zeis is infected?

cyst of zeis

waxy white, full of oily sebum

what happens when gland of moll infected?

clear fluid filled

what are the layers of the internal structure of the eyelid

outermost = skin

subcutaneous skin

striated muscle

submuscular connective tissue

fibrous tissue layer

non striated muscle

conjunctiva ( inner most)

what is dermatochalasis

lid laxity increase with age

describe the external skin on the eyelid

thinnest in the body

minimised weight = ease of mobility

constant movement w each blink

describe the subcutanous tissue

.oose areolar connective tissue contains no fat

therefore easy to stretch

can also get oedema or blood (‘black eye’)

what is the orbicularis oculi

surrounds orbital margin and divided into 3 parts

describe 3 parts of orbicularis oculi

palpebral = tre tarsal and preseptal ( involuntary lid movement) into eyelid

orbital = forced eyelid closure in temporal region and cheek

lacrimal is behind lacrimal sac

where does the orbicularis oculi originate

anterior part of medial palpebral ligmanet and adjacent bones

what is the lateral palpebral ligament

lateral point where the fibres interlace

what is the function of the orbicularis oculi (3)

forced closure of lids , pull eyebrows down ( orbital)

gentle closing of lids during blinking/sleep - soft voluntary closing = palpebral

aids movement of tears / pumping mechanism = lacrimal

what crnaial nerve innervates the orbicularis oculi

tempral and zygomatic branch

cr.n VII (facial)

what are two other muscles associated with orbicularis oculi

riolan’s muscle = marginal (edge) part of orbicularis oculi = maintain close position of lid margin to globe

horner’s muscle = surround lacrimal apparatus, important for tear draining

what is the location of the LPS ( levator palpebral superioris

at the apex of orbit

insert into pre tarsal skin of upper lid

what is function of levator palpebral superioris

anatagonist to orbicularis oculi - raises open upper eyelid

opening assisted by occipito frontalis muscle

describe innervation of levator palpebrae superioris

3rd cranial nerve ( superor division)

nerve also innervates several eoms

describe thhe exact locations and sizes of the levator palpebae superioris

coruses forward as muscle portion for40mm

descends vertically and fans out as strong white band of fibrous tissue as 15mm long.

2 assisting ligaments that act as levers or fulcrums to support movement

describe the structure of mullur’s muscle

palpebral (smooth muscle) = arise from fibres of LPS muscle in upper lid and from prolongation of inferior rectus muscle in lower lid

inserted in peripheral margin of tarsal plate

describe function of muller’s muslce

assists levator palpebrae superioris = helps keep lid raised when lps has already raised provides 2mm additional elevation to upper lid

describe innervation of muller’s muscle

fibres of sympathetic nervous system

what are the 3 main components of fibrous tissue that provide lid firmness, strneght and shape

tarsal plate = central thick part which contain meibomian glands, 10mm in height in upper lid and 5mm in lower lid in centre. upper and lower plate join at medial and lateral canthi

medial and lateral palpebral ligament = connection between tarsal plate and orbital margin

orbital septum = peripheral, thin part

what are the meibomian gland. describe their structure

long vertically orieted colecting duct

single glands at 1mm intervals

26-4 glands in the upper lid, 21-30 glands in lower lid

what are the 4 functions of the meibomian glands

secrete key oily component of tear film which is meibum = high lipid content

prevent evaporation of h20 aqueous layer

prevents tarsal secretion from mixing w water

prevent tears from spilling on lid

describe structure of orbital septum

thin membrane of connective tissue

seperates eyelid from contents of orbital cavity

perforated by orbital nerves, vesses and levator fibres

what is the function of the orbital septum

physical barrier to infection

oedema, or haemmorage

what are the palpebral ligaments

fibrous attachment sites

medial ligament = attached to frontal process of maxilla

lateral ligamanet = attached to whitnall’s turbercle ( laterally) and taral plate (medially)