Anatomy of the eye

Question 1

Name the labelled structures.

Answer 1

Clockwise from top right corner:

Orbital plate of the ethmoid bone

Nasal bone

Lacrimal bone

Maxilla

Zygoma

Superior orbital fissure (of sphenoid bone)

Sphenoid bone

Optic canal

Orbital plate of the frontal bone

Supraorbital notch/foramen

Question 2

Which bones/walls of the orbit are most vulnerable to damage in an orbital blowout fracture?

Answer 2

Medial wall- orbital wall of ethmoid bone

Floor- maxilla

Question 3

Which muscle acts as the “sphincter” of the eye?

Answer 3

Orbicularis oculi

Question 4

Which muscle raises the upper eyelid?

Answer 4

Levator palpabrae superioris

Question 5

What is the role of the orbital septum?

Answer 5

Prevents the spread of infection from the peri-orbit (superficial) to the orbit (deep)

Question 6

Name the labelled structures.

Answer 6

From top centre:

Iris (covered by avascular cornea)

Lacrimal lake

Inferior lacrimal papilla and punctum

Lower eyelid lined by conjunctiva

The conjuctival fornix (where conjunctiva reflects off the sclera onto the internal aspect of the eyelid)

White sclera covered by conjunctiva

Limbus

Location of the lacrimal gland

Question 7

Which nerve supplies the lacrimal gland?

Answer 7

Facial nerve

Question 8

Where does the nasolacrimal duct open into?

Answer 8

The inferior meatus of the nasal cavity

Question 9

What are the three layers of the eye?

Answer 9

Fibrous (cornea and sclera)

Uvea (vascular)

Retina (photosensitive)

Question 10

In the anterior segment, what are the roles of:

a) the iris
b) the lens
c) the ciliary body

Answer 10

a) controls pupil diameter
b) further refraction of light
c) controls the refractive shape of the lens and secretes aqeous humour

Question 11

What are the three chambers of the eye?

Answer 11

Anterior, posterior and vitreous body

Question 12

What are the contents of the anterior segment?

Answer 12

From anterior to posterior:

Cornea; anterior chamber; iris; lens; ciliary body; posterior chamber

Question 13

What are the contents of the posterior segment?

Answer 13

Vitreous body; 2/3rds of sclera; choroid; retina

Question 14

What is the path taken by aqeous?

Answer 14

Secreted by ciliary body; moves into the posterior chamber nourishing the lens; circulates past the lens into the anterior chamber nourishing the cornea; is reabsorbed into the scleral venous sinus at the iridocorneal angle

Question 15

What is the fovea centralis?

Answer 15

Area of most acute vision; area of the retina with highest concentration of cones

Question 16

What is the opthalmic artery a branch of?

Answer 16

The internal carotid artery

Question 17

What is an “end artery”? How does this relate to the eye?

Answer 17

An artery with insufficient anastamoses to maintain viability of the tissue supplied should an occlusion occur.

The central artery of the eye (first branch of the opthalmic artery) is an end artery

Question 18

Which vein drains the retina?

Answer 18

The central vein of the retina

Question 19

Where do the superior and inferior opthalmic veins drain to?

Answer 19

The cavernous sinus (inferior drains into superior initially)

Question 20

What does the blind spot of the visual field correspond to?

Answer 20

The optic disk

Question 21

How is vision affected by an obstruction in

a) a retinal artery branch or “branch” retinal vein
b) central artery or vein

Answer 21

a) visual loss corresponding to the area of ischaemia
b) complete monocular visual loss

Question 22

What are the three layers of the retina from posterior to anterior?

Answer 22

Photoreceptor cells; ganglia of photoreceptors; axons of photoreceptors

Question 23

Where are the visual cortices?

Answer 23

The right and left temporal lobes

Question 24

Where is light from the right visual field processed?

Answer 24

The left visual cortex

Question 25

How are spatial relationships in the visual pathways preserved?

Answer 25

Axons maintain specific spatial (both horizontal and vertical) relationships to each other

Question 26

Name the seven extraorbital skeletal muscles.

Answer 26

Four rectus (superior, inferior,medial, lateral)

Two oblique (superior and inferior)

Levator palpebrae superioris

Question 27

What does LR6 S04 AO3 mean?

Answer 27

Lateral rectus- abducens

Superior oblique- trochlear

All others- oculomotor