Eyelids

Question 1

List the eyelid tissue layers from anterior to posterior.

Answer 1

1. Skin.
2. Orbicularis muscle.
3. Tarsal plate (fibrous).
4. Levator muscle.
5. Muller muscle.

Question 2

The eyelid is anatomically divided into sections. How many and what are they called? What are they separated by?

Answer 2

1. 2 sections.
2. Lamellae.
3. Gray line - outermost margin of the orbicularis muscle.

Question 3

Where do the upper and lower lid sit in relation to the limbus?

Answer 3

1. Upper - 2mm below the superior limbus.
2. Lower - at the level of the inferior limbus.

Question 4

What does the anterior lamella contain?

Answer 4

Skin and orbicularis muscle.

Question 5

What does the posterior lamella contain?

Answer 5

Tarsal plate and conjunctiva.

Question 6

What is the orbital septum?

Answer 6

Fibrous sheet that originates from the fascia and periosteum of the orbital rim.

As the septal sheet descends to the aperture between the upper and lower lids, it becomes thicker and forms the tarsal plates.

Question 7

What is the function of the tarsal plates?

Answer 7

Maintain the shape of the eyelids.

Question 8

Why are the preaponeurotic fat pads posterior to the orbital septum useful?

Answer 8

Useful for categorising the depth of lacerations. If the fat pads are visible, then it is a deep laceration involving the posterior lamella.

Question 9

How many muscles of eyelid retraction are there? What are they?

Answer 9

1. 3 muscles.
2. Levator palpebrae superioris (main), Muller’s muscle and frontalis muscle.

Question 10

Which nerve is the levator muscle innervated by?

Answer 10

CN3.

Question 11

Which nerve innervates the frontalis muscle?

Answer 11

CN7 (facial nerve).

Question 12

What innervates the Muller’s muscle?

Answer 12

Sympathetic innervation.

Question 13

Which muscle is used in eyelid closure? Which nerve innervates this muscle?

Answer 13

Orbicularis oculi, CN7.

Question 14

What are the 3 afferent limbs of the blink reflex?

Answer 14

1. Corneal stimulus via CNV1.
2. Light stimulus via CN2.
3. Auditory stimulus via CN8.

Question 15

What is the efferent limb of the blink reflex?

Answer 15

Orbicularis oculi muscle via CN7.

Question 16

What is Bell’s phenomenon? What is a poor Bell’s phenomenon a risk factor for?

Answer 16

1. Normal physiological finding where the globe rotates up and out during forced lid closure.
2. Lagophthalmos - inability to fully close the lid.

Question 17

What do the canthal tendons do? Where do they attach?

Answer 17

1. Keep the eyelid structure stable.
2. They attach to the tarsus of the upper and lower eyelids.

Question 18

How many canthal tendons are there in each orbit?

Answer 18

2 - a medial and a lateral.

Question 19

What is the palpebral fissure?

Answer 19

Gap between the upper and lower eyelid margins.

Question 20

Describe the palpebral fissure abnormality for thyroid eye disease and state the mechanism for this.

Answer 20

1. Retraction.
2. Muller contraction.

Question 21

Describe the palpebral fissure abnormality for Horner syndrome and state the mechanism for this.

Answer 21

1. Ptosis.
2. Muller relaxation.

Question 22

Describe the palpebral fissure abnormality for CN7 palsy and state the mechanism for this.

Answer 22

1. Lagophthalmos.
2. Orbicularis weakness.

Question 23

Describe the palpebral fissure abnormality for CN3 palsy and state the mechanism for this.

Answer 23

1. Ptosis.
2. Levator relaxation.

Question 24

What is the risk of lagophthalmos?

Answer 24

Exposure keratopathy.

Question 25

What are the types of lid reconstruction (for lacerations)?

Answer 25

1. Direct closure - use of surrounding skin to close the excision. 2. Flaps - rotation of local skin to close the excision with intact blood supply. 3. Grafts - transplant of distant skin.

Question 26

What is the priority order of skin graft site?

Answer 26

1. Other lid. 2. Pre-auricular. 3. Post-auricular. 4. Underarm.

Question 27

Can you repair both lamellae with grafts? Why?

Answer 27

No because there would be no blood supply.

Question 28

What are the techniques used for anterior lamella repair?

Answer 28

1. Anterior advancement - incide and stretch tissue over the laceration. 2. Transposition - move tissue from the other lid. 3. Rotation - rotated skin from the cheek. 4. Glabella - rotated diamond-shaped forehead skin.

Question 29

What are the techniques used for posterior lamella repair?

Answer 29

1. Hughes flap - flap taken from the upper lid. 2. Free tarsal graft from fellow eye - tissue taken from the other eye.

Question 30

Which lamella is repaired first in a full thickness laceration of the lid?

Answer 30

Posterior (conjunctiva and tarsus) first then anterior (orbicularis and skin).

Question 31

What is blepharitis? What is the typical infection that causes it?

Answer 31

1. Chronic inflammation of the eyelid. 2. Typically associated with Staph aureus.

Question 32

What is affected by anterior blepharitis?

Answer 32

Base of the eyelashes.

Question 33

What are the 2 subtypes of anterior blepharitis?

Answer 33

1. Seborrhoeic (excessive secretions). 2. Staphylococcal (direct infection).

Question 34

What is affected by anterior blepharitis?

Answer 34

Meibomian glands.

Question 35

Which type of blepharitis has a better response to treatment? Why?

Answer 35

Anterior blepharitis because it occurs at the surface level.

Question 36

Describe the presentation of blepharitis.

Answer 36

1. Bilateral crusting of the lids and lashes. 2. Foamy tear film and meibomian cysts are seen specifically with posterior blepharitis. 3. Lashes appear normal in posterior blepharitis.

Question 37

What should recurrent unilateral blepharitis be investigated for?

Answer 37

Sebaceous cell carcinoma.

Question 38

What is the associated condition for staphylococcal blepharitis?

Answer 38

Atopic dermatitis.

Question 39

What is the associated condition for seborrhoeic blepharitis?

Answer 39

Seborrhoeic dermatitis.

Question 40

What is the associated condition for posterior blepharitis?

Answer 40

Acne rosacea.

Question 41

What is the management of blepharitis?

Answer 41

1. Lid hygiene. 2. Warm compress. 3. Topical lubrication and tetracyclines.

Question 42

What is meibomian gland dysfunction?

Answer 42

Chronic disorder of the meibomian glands that overlaps with posterior blepharitis, characterised by duct obstruction and abnormal glandular secretions which result in a characteristically foamy tear film.

Question 43

Describe the pathology of the meibomian gland dysfunction.

Answer 43

- Meibomian glands secrete a lipid layer which contributes to the tear film to keep it stable. - In MGD: secretion of the meibomian oil is obstructed → stagnation within glands → inflammation → staphylococcal infection → chronic inflammation and scarring.

Question 44

What is meibomianitis? What is it associated with?

Answer 44

1. Type of MGD where inflammation is marked. 2. Associated with acne rosacea and worse in the mornings with thick secretions and duct inflammation.

Question 45

Describe the presentation of meibomian gland dysfunction.

Answer 45

1. Foamy tear film. 2. Crusty eyelashes. 3. Gritty irritated eyes.

Question 46

What are the investigations and results of MGD?

Answer 46

1. Tear film breakup time of <5 seconds → tear film instability. 2. Fluorescein staining of the cornea shows corneal epithelial damage.