Lecture 2

Question 1

Answer 1

Question 2

Answer 2

Question 3

The orbit

Answer 3

The orbit is developed around the eye. It is roughly the shape of a quadrilatereal pyramid. The apex is at the optic foramen (optic nerve), and the base at the orbital margins.

Question 4

Conditions affecting the orbit

Answer 4

• Any large mass in the orbit will cause protrusion or displacement of the eye = proptosis
• Swelling of orbit contents (muscle) such as in thyroid eye disease will also cause proptosis (exophthalmos)

Question 5

Orbital bone fractures: Blow-out fractures

Answer 5

• Outward signs of haeorrhage
• Have to avoid a hit to the eye
• Orbital fat and EOM can become entrapped in the fracture.

Question 6

Foramen, fissure for nerve and blood vessel

Answer 6

Question 7

The optic foramen

Answer 7

The optic foramen facilitates for the optic nerve, ophthalmic artery, central retinal vein which traveks within the optic nerve out of the eye.

Question 8

Answer 8

Question 9

Which muscles are connected to movement of the eyelids?

Answer 9

• Levator palpebrae
• Orbicularis Oculi

Question 10

General structure of the eyelids

Answer 10

• The lid is a mobile and complex structure
• The structure of the lids including the tarsal plates and muscles causes characteristics folds and furow
• Caruncle = modified skin

Question 11

Eyelids- Tarsal plates

Answer 11

• Two thin plates
• One in upper and lower lid
• Dense connective tissue
• Provide structure to the lids

Question 12

Levator palpebral

Answer 12

• The Levator palpebral lifts the upper lid
• Starts from the sphenoid bone
• Runs horizontally forwards
• Lies between the superior rectus (an EOM) and the roof of the orbit
• At its end, the muscle fans out into a wide aponeurosis
• It passes into the tarsal plate of the upper eyelid.

Question 13

The lower lid

Answer 13

• There is close association with the inferior oblique muscle

Question 14

Orbicularis Oculi

Answer 14

• Has 3 parts: orbital, palpebral & lacrimal
• The orbital part is the largest
• It extends onto the face some distance beyond the orbital rim
• Some upper fibres are inserted into the eyebrow
  
  • These depress the eyebrow
• The fibres of the muscle pass around the orbit in concentric loops
• The palpebral portion is the central part & is confined to the eyelids

Question 15

Ptosis

Answer 15

• Droopy eyelid
• Can be congenital due to absence or poor levator function
• On down-gaze the levator may not relax and so the lid is ‘thethered’ up
• Can also be a sign of paralysis (3rd nerve)

Question 16

Entropion

Answer 16

• Entropion is the turning in or inversion of the lid
• Also turns the eyelashes towards the eye - watery eye
• Over time can cause scarring of the cornea, therefore visual impairment

Question 17

Ectropion

Answer 17

• Ectropion is the turning out or eversion of the lid, usually the lower lid
• Causes the eye to ‘weep’
• Can cause dry eye
• Congenital
• More common with age

Question 18

Function of eyelids

Answer 18

Protection

• From injury, startle reflex
• From light, help regulate light into the eye
• When closed, brain can rest

Essential for the flow of tears

• Assist secretion of tears
• Spread teards across eye, blink reflex
• Assists the removal of tears from the eye
• Vital to moisture and nourish the cornea