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OpAnatomy > Eyelid > Flashcards

Eyelid Flashcards

1
Q

basic functions of eyelid? (6)

A

mechanical defense.
optics - spreading tear film - smooth optical surface. reduce visual stimuli
provide hydration (prevent xerosis - drying)
provide corneal nutrition and gas exchange
contraction of eyelid –> meibomian gland secretion

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2
Q

What are the assisting structures of the eyelid and conditions associated with them?

A

Cilia
Lasts 3-5months
Sparser as age
Results in reflex lid action
Trichiasis – misdirection of eyelash growth

Brow
Mobility – assist lid mobility (frontalis muscle contraction elevates lid, orbital orbicularis contraction depresses lid)
Expression
Ptosis – attempt to elevate drooping eyelids

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3
Q

What is the normal palpebral aperture?

A

Average length ~29mm
Average width ~9.5mm
Upper lid overlaps superior cornea ~1mm
Lower lid sits just below or on inferior limbus

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4
Q

What are some variations (conditions) of palpebral aperture?

A

Ptosis – drooping of upper eyelid
Exophathalmos – forward protrusion of the globe
Endophthalmos – backward position of the globe

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5
Q

What is the pressure zone, what is its purpose and what is the pressure?

A

portion of lid contacting globe - just posterior to marx’s line

due to tarsal plate curved to contour of globe, muscle of riolan, medial and lateral palpebral ligaments pulling eyelids into place.

purpose - rovide even spreading of tears, notifying that eyelid is closed.

pressure 8+-3.4mmHg

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6
Q

condition where lid margin is turned away from globe?

A

ectropion

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7
Q

What is it called when the lid margin is turned towards the globe?

A

Entropion

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8
Q

Explain Lid wiper epitheliopathy. what do patients with LWE also experience?

A

when epithelial cells at lid margin dry out and devitalise (die) –> scraping against eye (damage)

76% of patients with LWP also had dry eye symptoms

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9
Q

What can cause lid closure?

A

Gravity
Orbicularis oculi contraction
Levator relaxation

Note: levator relaxes as orbicularis contracts

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10
Q

How do the lids close (direction of upper and lower lid) and what is the speed?

A

There is a greater movement of the upper lid compared to the lower lid
The upper lid moves downwards and slightly nasally
The lower lid primarily moves horizonatally – nasally

Closing phase ~82ms
Opening phase ~176ms
Total duration ~258ms

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11
Q

What happens to the eye location when you blink

A

Normal blink – eye moves slight down in movement
Forced blink – large upwards and outward movement
Globe retraction accompanies blinking

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12
Q

What are the two anomalies of eye movements?

A

Marcus Gunn – jaw winking phenomenon
Bell’s Palsy – 7th nerve (prevents eye blinking)

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13
Q

What are the classes of Lid closure (with subclasses)

A

Voluntary
- Bilateral
- Unilateral

Involuntary
- Spontaneous blink
- Reflex blink
- Blepharospasm (involuntary forcible eyelid closure –
overstimulation of facial nerve)
- Reflex
- Spontaneous

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14
Q

types and pathways of reflex blinks

A

Touch (cornea)
A – trigeminal nerve (CNV)
E – facial nerve (CNVII)
Dazzle (light)
A – optic nerve (CNII)
E – facial nerve (CNVII)
Menace (menacing visual stimulus)
A – optic nerve (CNII) – more visual processing
required
E – facial nerve (CNVII)
Proprioceptive – stretch reflex of the orbicularis

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15
Q

What is the mean blink rate of spontaneous blinks and its primary purpose?

A

14 blinks/min
Maintenance of tear film

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16
Q

What can change the interblink ratio?

A

variable from person to person

Age, climate, robustness of tears, tasks, environment (dusty etc), neurological, contact lenses

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17
Q

What are the four types of lid closure? And which contribute to conjunctival drying?

A

Complete
Incomplete – causes xerosis
Twitch – can potentially cause xerosis
Forced

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18
Q

What happens to vision during blinking?

A

During spontanteous blinks, vision is suppressed to allow for smooth visual information

19
Q

What happens to the eyelid muscles when you sleep? What is it called when incomplete lid closure while sleeping?

A

relaxation

nocturnal lagophthalmos

20
Q

What are the layers of the eyebrows and what is their purpose?

A

Skin (thick and mobile)
Subcutaneous tissue (connective tissue layer attaching skin to muscle – movement)
Muscle layer (movement)
Submuscular areolar layer (loose connective tissue allowing free movement)

21
Q

What’s the smooth skin between your eyebrows?

A

Glabella

22
Q

What are the muscles acting on the eyebrow and what do they do in terms of brow movement?

A

Orbicularis Oculi (orbital portion)
Shuts lids firmly and draws forehead skin medially
depressing eyebrows (mad)
Corrugator
Draws brows medially
Frontalis
Elevates brow and draws scalp forward
Procerus
Draws brows medially

23
Q

What nerve are the eyebrow muscle innervated by?

A

Facial nerve (7th cranial nerve)

24
Q

What are the major components of the eyelids?

A

Skin (thin, elastic)
Subcutaneous areolar tissue (loose CT, no fat)
Striated muscle (orbicularis oculi)
Submuscular areolar tissue
Tarsal plates (contains meibomian glands)
Orbital septum
Non-striated muscle (Muller’s muscle)
Conjunctiva
Accessory glands (Moll, Zeis, Krausse and Wolfring)
Cilium

25
Q

Why are the tarsal plates essential to the eyelid? Give two reasons

A

Tarsal plates are made of dense connective tissue (primarily collagen) giving strutural rigidity as the extend the width of the lid and curve to fit the contour of the globe

Divides lid into tarsal and septal portions – superior and inferior palpebral sulcus

26
Q

Tarsal plate dimensions?

A

Width ~29mm
Upper height ~10mm
Lower height ~5mm

27
Q

How many meibomian glands in each eyelid?

A

Superior – up to 40
Inferior – up to 30

28
Q

What is it called when a meibomian gland becomes blocked?

A

STI

29
Q

Explain the secretions from the Meibomian glands (what and how)

A

The meibomian glands secrete the lipid component of the tear film onto the eyelid margin with every blink. This is because the contraction of the pretarsal and marginal (Riolan) orbicularis muscle mechanically assists with secretion of Meibomian lipids.

30
Q

How does the levator palpebrae superious initiate lid opening? (insertion and innervation)

A

Innervated by the Oculomotor Nerve (III)

Initiates lid opening through tendon extending and branching becoming the levator aponeurosis which travels through the superior transverse Whitnall’s ligament pulling the levator upwards. The levator aponeurosis inserts into anterior surface of the tarsal plate and connective tissue surrounding the orbicularis oculi. Thus when the levator palpebrae superioris contracts, the lid is drawn upwards (strongest muscle).

31
Q

What is the assisting muscle of lid opening and its innervation?

A

Muller’s Muscle (superior and inferior tarsal muscle)
Smooth muscle innvervated by sympathetic system

32
Q

What is Ptosis

A

Drooping of lids

Can be sympathetic or parasympathetic (both part of lid opening)

Oculomotor (levator palpebrae superious) paralysis results in larger degree of ptosis

More subtle with sympathetic

33
Q

What muscles are responsible for lid closure?

A

Palpebral portion and orbital portion of the orbicularis oculi – innervated by facial (VII)

Medial and lateral palpebral ligaments – anchor muscle to the orbit

Marginal or ciliary portion of Muscle of Riolan and lacrimal portion (Horner’s Muscle- assists with tear drainage)

34
Q

How many lashes in the upper and lower eyelids?

A

Upper ~100
Lower ~50

35
Q

Explain the Gland of Zeis?

A

Sebaceous gland associated with lash follicles (only secretions)

36
Q

Explain the Gland of Moll?

A

Modified sweat gland not associated with lash follicle

37
Q

What are the conjunctivial zones?

A

Superior Bulbar Conjunctiva
Superior Fornix
Scleral conjunctiva
Limbal conjunctiva
Superior Palpebral conjunctiva
Orbital conjunctiva
Tarsal conjunctiva
Marginal conjunctiva

38
Q

define conjunctiva?

A

translucent mucous membrane covering ocular surface, including posterior surface of eyelid.

39
Q

Explain secretory cells of the conjunctiva and where they are most densely located?

A

Goblet cells in conjunctival epithelium produce mucous component of the tear film

Located most densely infero-nasally (near caruncle)
Caruncle most dense

40
Q

discuss orbital septum

A

Thin, dense connective tissue from the orbital rim to the tarsal plates

Separates and protects eyes from orbital fat, preventing forward movement of orbital fat into the eyelids

41
Q

Where is the epicanthus located and what does it do?

A

It eliminates the superior fissure
Located at the caruncle

42
Q

What is the purpose of the plica semilunaris?

A

Fold of conjunctival tissue medially next to the caruncle

Allows lateral eye movement without stretching the conjunctiva

43
Q

What is the main blood supply of the eyelids?

A

The lateral and medial palpebral arteries merge to give form the palpebral arcades (upper marginal and peripheral arcades and lower marginal arcade)

44
Q

What are the lateral and medial lymphatic drainage of the eyelids?

A

Lateral: preauricular and deep parotid nodes
Medial: submandibular nodes

OpAnatomy (9 decks)

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