Eyelids & Third Eyelid Flashcards
When do the eyelids develop during gestation? What are they developed from?
Develop around day 25 of gestation
Grow towards each other and elongate to cover developing eye
Meet and fuse together by day 40
Eyelid epidermis, cilla, lacrimal gland, nictitans gland, meibomian glands and sweat/sebaceous glands (glands of Moll and Zeis) all derived from surface ectoderm.
Neural crest mesenchyme contributes to development of tarsal plate and dermis
Eyelid muscles derived from mesoderm
When do puppies/kittens first open their eyes post birth?
Eyelids separate day 10-14 postnatally
What layers are there within the eyelids?
1.Haired eyelid skin on outer surface
2. Muscle extending to a fibrous tarsal plate containing meibomian glands (tarsal plate poorly developed in dog, more developed in the cat)
3. Palpebral conjunctiva on inner surface extending to conjunctival fornix where reflects to become bulbar conjunctiva covering sclera.
Describe the arrangement of cilia (eyelashes) in the dog and cat.
Upper eyelid = two or more rows of cilia in the dog, cats first row of skin hairs is more developed and act as cilia
Neither cats nor dogs have cilia on bottom eyelids
Which muscle controls the closing of the eyelids? Which eyelid is more mobile - upper or lower?
Orbicularis oculi = closure of the palpebral fissure and enables blinking
(Upper eyelid more mobile than lower eyelid - greater coverage of cornea with each blink)
What is the innervation to orbicularis oculi (muscle responsible for closure of the palpebral fissure)?
Palpebral branch of the auriculopalpebral nerve - branch of the facial nerve (CN 7, VII)
Which muscles are involved in opening of the eyelids?
Levator palpebrae superioris (upper eyelid)
Pars palpebralis of sphincter colli profundus (lower eyelid)
Muller muscle (upper eyelid)
Which nerve innervates the levator palpebrae superioris? What benefit does this innervation have in relation to another structure of the eye?
Innervated by occulomotor nerve (CN III)
Occulomotor also innervates the dorsal rectus EOM - means that upper eyelid lifts at same time as globe elevated.
Which nerve innervates the pars palpebralis of sphincter colli profundus?
Dorsal buccal branch of facial nerve (CN VII)
What is the innervation to the Muller muscle?
Smooth muscle = sympathetic innervation
Where do the upper and lower eyelids meet? How is this structure stabilised?
Meet at the canthi - medial and lateral canthus
Medial and lateral canthal tendons to stabilise + retractor angularis oculi muscle
Describe the medial and lateral canthal tendons.
Medial canthal tendon = distinct fibrous band originating from periosteum of frontal bone
Lateral canthal tendon = musculofibrous band lying subconjunctivally connecting to muscle at lateral canthus to orbital ligament
How is sensation provided to the eyelids?
Branches of the ophthalmic and maxillary nerves originating from the trigeminal (CN 5)
Ophthalmic nerves = mainly medial
Maxillary = mainly lateral
but is some overlap
What reflex will be absent if there is loss of sensation to the eyelids?
Trigeminal lesion - loss of palpebral reflex
Assess palpebral at both medial and lateral canthus
How can you differentiate the loss of the palpebral reflex due to a trigeminal or a facial nerve lesion?
Observation of spontaneous blinking - indicates facial nerve intact (innervates orbicularis oculi - muscle responsible for blink)
What does the grey line or margo-intermarginalis represent?
Slight groove - opening of meibomian glands
What are the meibomian glands - how many are there per eyelid and what do they secrete?
Modified sebaceous glands
20-40 glands per eyelid
Visible through palpebral conjunctiva when eyelid everted
Produce meibum - lipid faction of the tear film
What is the role of meibum in the tear film?
Meibum = liquid at body temperature
Expressed from meibomian glands during blinking
Decreases surface tension of tear film drawing water in and increasing tear film thickness.
Reduces evaporation and coats eyelid margins to minimise tear overflow onto eyelid margin itself.
What are the glands of Moll & Zeis?
Moll = modified sweat glands
Zeis = sebaceous glands associated with eyelid cilia
Functional significance in animals unknown but can become infected resulting in eyelid styes/external hordeola.
What is the caruncle?
Caruncle = protuberance at medial canthus from which fine hairs project
Where is the third eyelid derived from embryonically?
Surface ectoderm
Describe the anatomy of the third eyelid/nictitans.
Central T shaped hyaline cartilage surrounded by fibrous tissue and covered in conjunctival epithelium
Bulbar surface = lymphoid tissue beneath conjunctival epithelium + intraepithelial goblet cells
Goblet cells also present in greater number on palpebral conjunctiva of TEL
Nictitans gland located at the inferior/proximal end of the cartilage
Base of third eyelid associated with fascia of the orbital musculature and cartilage shaft is aligned with inferionasal peribulbar connective tissue.
Does the TEL contain muscle?
Canine TEL = Thought to lack musculature - protrusion being passive when globe retracted and retrobulbar tissues push on base of TEL but leiomyomas have been diagnosed in the TEL indicating the presence of native smooth muscle.
Feline TEL = contains both smooth and striated muscle, can actively retract and protrude respectively
2 sheets of smooth muscle (medial and inferior muscles of TEL) arise from deep in orbit from fascia of medial and ventral rectus muscles
Medial supplied by postganglionic fibres of infrtrochlear division of ophthalmic branch of trigeminal
Inferior supplied by intraorbital/zygomatic branches of maxillary branch of trigeminal nerve
Striated muscle - arranged as leashes
Extend from levator superioris and lateral rectus - insert on dorsolateral and ventrolateral arms of TEL
Ventrolateral = abducens innervation
Dorsolateral = occulomotor
What types of disease can cause passive protrusion of the TEL?
Retrobulbar/orbital disease - space occupying lesions (extraconal)
Reduced globe size = microphthalmos, phthisis bulbi
List the functions of the eyelids.
Protection of the eye (menace response)
Cilia and sensory vibrissae contribute to protective effect
Meibomian glands of eyelids = meibum for tear film
Goblet cells in palpebral conjunctiva = mucin for tear film
Blinking - removal of debris from ocular surface, distribution of tear film (nutrition and hydration to ocular surface), draining tear film to remove toxic waste (blinking = pressure change in lacrimal sac which draws tears into lacrimal canaliculi, as eyes open pressure put on lacrimal sac to push tears down NL duct)
List the functions of the third eyelid.
Nictitans gland - 30% to one third aqueous produced + Immunoglobgulin secreting plasma cells have been identified adjacent to conjunctival epithelium on both surfaces of the third eyelid - role in defence of ocular surface.
Leading edge distributes the tear film and physically removes debris from the corneal surface
Describe the steps of particular importance in assessing a patient for eyelid disease.
Distance exam - look for asymmetry in ocular/adnexal conformation and periocular skin changes, ocular discharge
Look at distribution of any discharge as can give clues to area of cilia contact.
Presence/absence of spontaneous blinking
Hands on focal examination with naked eye and light source +/- magnificatiojn
Eyelids examined systematically - particular attention to periocular skin, eyelid margins and palpebral conjunctiva.
Assessment of meibomian glands
Assessment of lacrimal punctae
If entropion - application of topical anaesthetic should be applied to assess for any spastic component
Corneal ulceration - look at adjacent eyelids for any inciting cause of the ulcer e.g ectopic cilia
Fluorescein - identify ulceration, TFBUT, NL patency, adheres to any facial hairs/distichia contacting corneal surface and can make easier to identify.
Discuss the important steps when examining a patient for suspected TEL disease.
Presence confirmed and palpebral surface + leading edge examined
Gentle globe retropulsion can be used to passively protrude TEL and check for any restriction to protrusion (prev surgery/disease)
Topical anaesthesia - examine under TEL - blunt tipped cilia forceps or micro St Martins to grasp palpebral surface and retract
Anaesthesia of the conjunctiva takes longer than cornea so optimal = application of cotton tipped swab soaked in local anaesthetic directly over area of TEL to be grasped.
What laboratory tests may be indicated in cases of eyelid disease?
Cytology using tape strips - identify bacteria and yeast colonisation of periocular skin
Swabs for bacterial culture/sensitivity - ulcerated skin lesions or discharge from abnormal meibomian glands
Periocular skin scrapes/hair plucks = parasitic disease
FNA - eyelid masses
Surgical biopsy - punch biopsy of periocular skin, full thickness eyelid mass wedge resection if eyelid margin involved, biopsy of eyelid masses
Biopsies - histopath +/- immunohistochemistry +/- PCR or tissue culture
What laboratory tests might be indicated in cases of third eyelid disease?
Cytlology of palpebral conjunctiva - topical anaesthesia and scalpel blade blunt end
Conjunctival snip biopsies after topical anaesthesia
Larger biopsies - GA, avoid leading edge of TEL as will affect TEL function
What can occur if the eyelids open prematurely?
Lacrimal apparatus still immature
Keratitis, corneal dessication, conjunctivitis and risk of severe corneal ulceration risking perforation and endophthalmitis
Treatment - frequent lubrication and possibly temporary tarsorrhaphy
What is delayed opening of the eyelids termed and why does it occur?
Ankyblepharon
Failure of bridge between two eyelids to atrophy
(Reported in Persians)
What is ophthalmia neonatorum? What is the recommended treatment?
Accumulation of fluid/pus beneath fused eyelids of the neonate.
Recommended tx = warm compresses and gentle digital traction to encourage eyelid opening
If conservative approach unsuccessful over 24hrs then eyelids can be very carefully prised apart using blunt ended instrument e.g fine haemostats or blunt ended scissors
NEVER incise with scalpel or scissors as will cause irreversible damage to eyelid margins
Once palpebral fissure opened topical AB ointment should be applied - lubrication + AB cover
Which infectious disease is associated with ophthalmia neonatorum in cats?
What complications can be seen with this type of infection?
Herpesvirus - if occurs before eyelids open conjunctival and corneal epithelium can undergo necrosis and neutrophilic response leading to accumulation of inflammatory debris in conjunctival sac distending the still fused eyelids. Can then get secondary infection on top.
Complications - symblepharon, corneal ulceration/perforation, endophthalmitis/panophthalmitis
What is an eyelid coloboma?
Congenital defect - partial or full thickness length of eyelid is absent (whole length = eyelid agenesis)
Where do eyelid colobomas usually occur in dogs?
Usually lower lateral eyelid that is missing in dogs
Can be unilateral or bilateral
Less common than in cats and may be associated with other defects e.g dermoids
Where do eyelid colobomas usually occur in cats?
One of the most common feline congenital abnormalities
Usually lateral upper eyelid and bilateral (medial canthal involvement also reported)
Reported in DSH, Persian and Burmese
Can vary from small notch to complete absence of tow thirds or more of upper eyelid and lining.,
What are the consequences of eyelid colobomas?
Increased corneal exposure - increased evaporation of tears
Poor tear film distribution
Keratitis and corneal ulceration
Trichiasis - adjacent skin hairs contact cornea
What treatment options are there for eyelid colobomas?
Very mild cases - regular lubrication
Cryoepilation of offending hairs if eyelid sufficient enough to function and protect cornea.
Impaired eyelid function/severe trichiasis - requires surgical correction
Small defects - wedge resection
Larger defects = more complicated grafting techniques
Option 1: Skin-orbicularis layer from lower eyelid and conjunctiva from third eyelid - graft contraction can occur and trichiasis meaning further procedure required.
Option 2: Modified 2 stage Mustarde cross lid technique - full thickness lower eyelid to reconstruct upper eyelid avoiding trichiasis associated with other methods
Lip to lid technique then used to repair defect in lower eyelid
Option 3 : Modified lip to lid technique by taking section of commissure of lip and using it to replace upper eyelid and lateral canthus - 1 stage technique, good cosmetic and function result.
Option 4: Subdermal collagen + modified Stades procedure to remove haired skin in contact with cornea
Option 5: Free oral mucosal grafts
Option 6: Subdermal hyaluronic acid injections and free labial mucocutaneous grafts.
What is a dermoid? How do they present and what is the usual treatment in the eyelid?
Presence of aberrant tissue containing skin
May occur as result of abnormal differentiation of group of cells or inclusion of surface ectoderm during closure of foetal clefts.
May affect conjunctiva and eyelids
Often referred to as choristomas - normal tissue in abnormal location (eyelids hamartomas)
Mostly unilateral although occasionally bilateral
Tx = removal of abnormal tissue surgically with repair and re-establishment of eyelid margin
Fissure length usually enough to allow direct closure via wedge resection without need for blepharoplastic techniques.
What breed has a predisposition for dermoids in cats?
Birmans/Burmese
What is a macropalpebral fissure? Which breeds is it commonly seen in?
Enlarged palpebral fissure
Usually bilateral
St Bernards, Neapolitan Mastiffs, Clumber Spaniels, Bloodhounds - overlong eyelids + weak lateral canthal support = ectropion frequently combined with lateral lower entropion = diamond eye appearance
Brachycephalics - orbits shallow and eyelids are taut - overlong eyelids = exposure keratitis and risk of proptosis
What is lagophthalmos? What can cause it? What treatment options are there?
Inability to close eyelids
Causes:
Facial nerve paralysis - prevents eyelid closure
Brachycephalics - prominent globes, macropalpebral fissure, leads to incomplete blink = central corneal dessication, poor tear film distribution, exposure keratitis with associated neovascularisation and ulceration.
May not fully be able to close eyelids even when asleep.
Cats e.g Persians = risk of corneal sequestrum formation
Tx - regular ocular lubrication (oil based tear substitutes - long lasting)
Surgery - shortening of eyelids - medial canthoplasty
What is a micropalpebral fissure - which breeds can it occur in?
Abnormally small eyelid fissures - Shetland sheepdog, Rough Collie, Schipperke
No tx usually indicated
Tight eyelid globe apposition can lead to reduction or abolition of lacrimal lake leading to epiphora.
Define distichiasis.
Distichiasis = extra eyelashes arise from follicles adjacent to meibomian gland orifices.
1 hair = distichia
More than 1 hair from single orifice - distichiasis
Which breeds of dog are predisposed to distichiasis?
Flat coated Retriever, Dachshund, Cocker Spaniels, Miniature Poodle, Shetland Sheepdog, Bulldog, Boxer, Cavalier, Pekingese, Weimaraner, Staffordshire Bull Terrier
How do you determine the significance of distichiasis?
Many distichia are fine and have had from young age - incidental findings that do not require treatment
If dog presents with ocular discomfort and distichia - perform full ophthalmic exam to rule out other causes.
Problems in older dog or unilateral issue where distichia appear equally distributed bilaterally - distichia unlikely to be responsible
If in doubt - assess response to epilation before considering permanent removal techniques.
What permanent removal techniques are there for distichia?
Solitary - eyelid wedge resection
Multiple distichia:
Cryotherapy
Electrolysis
Radiosurgery - specialised distichiasis wires are used to treat each follicle individually
Transconjunctival thermal electrocautery
Sharp knife surgery
How is cryotherapy for distichia performed? What advantages does it have?
How are these patients managed post op?
Advantages - scarring minimised and meibomian glands can recover as hair follicle differentially temperature sensitive
Good for treating more extensive areas of distichiasis and treating any un-erupted hairs at time of tx
Chalazion clamp applied to stabilise and evert eyelid, limits blood supply for more rapid freezing and slower thawing increasing effectiveness
Cryoprobe or cryospray applied transconjunctivally
Ideally thermocouple at tip to measure temperature and ensure adequate freezing of the hair follicle without permanent damage to adjacent epidermal or conjunctival surfaces.
Operating microscope/magnification improves precision.
Double freeze-thaw cycle used
Post op = eyelid swelling to be expected
NSAIDs for analgesia/anti-inflammatory
Eyelid depigmentation often occurs but should re-pigment over 2-6 months
20% recurrence rate
How is electrolysis performed - what are the disadvantages of this procedure for distichiasis?
Disadvantages - time consuming, scarring and distortion of eyelid margins can occur as can irreversible meibomian gland damage.
Procedure can only be used for hairs erupted at time and because distichia growth is cyclical procedure may have to be repeated as new hairs emerge.
How is transconjunctival thermal electrocautery for distichiasis performed?
Disposable thermal electrocautery pen used with magnification
Tip is heated and inserted into palpebral conjunctiva at level of distichia - 4mm posterior to eyelid margin and 2mm depth
Distichia then easily epilated
Glandular contents then additional distichia expressed using cilia forceps inserted into conjunctival defect
Charred tissue should be debrided to reduce risk of corneal ulceration
Complications - eyelid depigmentation/inflammation, infection, eyelid distortion, qualitative tear film abnormality
Unable to use for medial distichia due to proximity to lacrimal punctae and canaliculi
What is sharp knife surgery for distichiasis? What disadvantages does it have?
Lid splitting/subconjunctival resection of strip of follicles
Disadvantages = incomplete resection, eyelid distortion and/or cicatricial entropion
Hotz-celsus to direct hairs away from cornea but affects relationship between eyelid margin and ocular surface
What can be the consequences of distichiasis and ectopic cilia in cats - which breeds predisposed and how common?
Not very common in cats
Burmese/Siamese appear to be predisposed
Epiphora, corneal ulceration, sequestrum formation
What are ectopic cilia? What is the treatment for them?
Atypical form of distichia - arise from follicle inside meibomian gland or near meibomian duct.
Contrast to distichia emerge through conjunctival surface few mm from eyelid margin and are directed towards cornea.
Solitary or in small clumps
Young dogs - usually middle of upper eyelid
Often occur in conjunction with distichia
Treatment = resection en bloc using chalazion clamp and no 11 blade or 2mm biopsy punch
Surgical site can then be treated with cryotherapy to reduce reoccurrence.
What is trichiasis - where can these hairs originate from?
Normally located but abnormally directed hairs that contact and irritate ocular surface
-Upper eyelid cilia
- Caruncular hair
-Nasal fold/facial hair
-Hair adjacent to areas of eyelid agenesis
- Misaligned eyelid margin following trauma without surgical repair
-Misaligned eyelid margin from poor surgical repair
-Blepharoplasty techniques involving transposition of facial skin without creating an eyelid margin (Sliding lateral canthoplasty, H-plasty, sliding skin grafts)
- Abnormal eyelid position (e.g entropion)
Treatment depends on clinical significance i.e = is the trichiasis causing corneal pathology
What types of entropion are there?
- Breed related/anatomical
- Spastic
- Cicatricial
- Atonic/senile
How does anatomical/breed related entropion usually present?
Usually bilateral (occasionally unilateral)
Breeds predisposed - Shar Pei, Chow-Chow (often evident soon after eye opening)
4-12 months of age as facial conformation changes can become more evident, some cases may reduce/improve as matures.
Breed related entropion may also develop in middle aged animals, typically males - associated with s/c deposits, often upper eyelid entropion.
Optimal method of correction varies with breed/predisposing anatomy.
Entropion of this nature likely to be hereditary so dogs who have surgical alteration of facial conformation should not be bred from.
What is spastic entropion?
Secondary entropion that results from ocular pain
Spasm of orbicularis oculi and retraction of the globe causing eyelid to turn in.
Resultant trichiasis worsens ocular pain and retraction.
Most forms of entropion will have spastic component so important to assess post application of local anaesthetic.
What is cicatricial entropion?
Uncommon - results from lid distortion and scarring following injury, chronic dermatitis or inappropriate surgery
What is atonic/senile entropion?
Age related loss of skin elasticity and muscle tone
Often breeds that already have excessive facial skin e.g Cocker Spaniel (forehead skin droops upper eyelid cilia directed downwards - contact cornea and lower conjunctival fornix - conjunctivitis/keratitis
How should you assess entropion prior to performing correction?
Assess in conscious patient
Local anaesthetic applied - removes spastic component and avoids over-correction
Assess in different head positions - especially with head down as entropion/ectropion may be exacerbated by slippage of facial mask. (examination table to help)
Observation of tearing and ocular discharge will also give clues as to problematic area.
How can entropion be addressed in young puppies?
Corrective surgery best delayed until 5-12 months (depending on progression, breed and degree of entropion)
Eyelid conformation can change as puppy ages so some cases will self correct with time.
Temporary correction always indicated - periocular hairs rubbing on cornea = pain, globe retraction, worsening of entropion and risk ulceration/scarring and potentially perforation.
Lembert suture pattern - non absorbable interrupted sutures to create temporary eversion
Sutures perpendicular to eyelid margin
1st bite 2-3mm from eyelid margin
Several rows may be needed in breeds with excessive skin e.g Shar Pei
Sutures can be pre-placed and tissue glue placed in presumptive skin fold that will be formed before tying the sutures in order to help prolong the eversion
Sutures directed away from cornea
May need to be repeated if sutures fail or entropion recurs before puppy old enough for permanent correction
Alternatives
If just lower lateral entropion = temporary tarsorrhaphy
Skin staples (often several rows)
Hylauronic injectable subdermal filler
What options are there for entropion correction in adults?
No “one size fits all” treatment - depends on location of entropion and surrounding anatomy
Options include:
Hotz-Celsus (lower entropion)
Stades procedure (upper entropion)
Medial canthoplasty
Coronal rhytidectomy
Wedge resections (overlong eyelids)
What surgical corrections can be performed for overlong eyelids?
Wedge resection
Wedge resection + Hotz celsus
Modified Kuhnt-Szymanowski technique (support lateral canthus)
Predisposed - Chow Chow, Labrador, Shar Pei, Setters
