Applied Anatomy and Physiology of the Eye

Question 1

From what structure does the central nervous system develop?

Answer 1

The neural tube.

Question 2

At what week of gestation do the optic vesicles develop the eyes?

Answer 2

Between the 3rd and 10th week of gestation.

Question 3

Name the three layers of the eye.

Answer 3

Outer fibrous coat, middle vascular layer, neurosensory layer.

Question 4

What structures make up the outer fibrous coat of the eye?

Answer 4

Sclera and cornea.

Question 5

What structures are part of the middle vascular layer of the eye?

Answer 5

Iris, ciliary body, choroid.

Question 6

What are the components of the neurosensory layer?

Answer 6

Retinal pigment epithelium and neurosensory retina.

Question 7

What is the volume of the eye globe?

Answer 7

7cc.

Question 8

What is the axial length of the eye globe?

Answer 8

23-25 mm.

Question 9

What are the components of the anterior chamber of the eye?

Answer 9

Aqueous humour, lens, vitreous body.

Question 10

What are the accessory structures of the eye?

Answer 10

Eyebrows, eyelids, eyelashes, lacrimal apparatus, extraocular muscles.

Question 11

What is the conjunctiva?

Answer 11

A transparent membrane overlying the eyeball and lining the eyelids.

Question 12

What is the sclera?

Answer 12

The white of the eye, forming 5/6 of the outer coat.

Question 13

What is the thickness of the sclera at the point where the optic nerve pierces it?

Answer 13

0.1 mm (at the lamina cribrosa).

Question 14

What is the primary function of the sclera?

Answer 14

It helps maintain the shape of the eyeball and provides attachment for extraocular muscles.

Question 15

What is the cornea and its function?

Answer 15

The transparent anterior 1/6 of the outer coat, responsible for refraction.

Question 16

How much of the vision is provided by the cornea’s refractive surface?

Answer 16

70% of vision.

Question 17

What is the dioptric power of the cornea?

Answer 17

+43D to +45D.

Question 18

What is the iris, and what function does it serve?

Answer 18

A coloured diaphragm with a central aperture (the pupil); controls light entry.

Question 19

What are the two groups of smooth muscle fibres in the iris?

Answer 19

Circular (sphincter pupillae) and radial (dilator pupillae) muscles.

Question 20

What is the function of the ciliary muscle?

Answer 20

Accommodation (focus adjustment).

Question 21

What is the main function of the ciliary processes?

Answer 21

Production of aqueous humour.

Question 22

Where is the choroid located?

Answer 22

Between the sclera and retina.

Question 23

What layers depend on the choroid for nutrition and blood supply?

Answer 23

The outer layers of the retina (up to the outer nuclear layer).

Question 24

What is the retina, and how many layers does it have?

Answer 24

The neurosensory layer of the eye, composed of ten layers.

Question 25

What is the function of the macula?

Answer 25

Sharp, detailed vision.

Question 26

What is the location and function of the optic disc?

Answer 26

Located nasally, it aggregates nerve fibres (optic nerve) and is 1.5 mm in diameter.

Question 27

What is the volume and composition of aqueous humour in the eye chambers?

Answer 27

0.25 ml in the anterior chamber and 0.06 ml in the posterior chamber; aqueous humour is similar to plasma but has higher concentrations of ascorbate, pyruvate, and lactate.

Question 28

How is aqueous humour produced?

Answer 28

Produced by the non-pigmented ciliary epithelium, at 2-3 µl/min.

Question 29

What is the normal intraocular pressure range?

Answer 29

10-21 mmHg (by applanation).

Question 30

What is the function of the crystalline lens?

Answer 30

A biconvex, transparent structure that focuses light.

Question 31

What is the volume of the vitreous humour in the eye?

Answer 31

4-4.5 ml of transparent gel.

Question 32

Name the extraocular muscles responsible for the movement of the eyeball.

Answer 32

Medial rectus, lateral rectus, superior rectus, inferior rectus, superior oblique, inferior oblique.

Question 33

What is the primary artery supplying blood to the eye?

Answer 33

Ophthalmic artery (branch of internal carotid artery).

Question 34

What veins are involved in the venous drainage of the eye?

Answer 34

Short and anterior ciliary veins, vortex veins, central retinal vein.

Question 35

Name the motor nerves that supply the eye.

Answer 35

Oculomotor (3rd CN), trochlear (4th CN), abducens (6th CN), facial (7th CN).

Question 36

What sensory nerve supplies the whole eye?

Answer 36

Trigeminal nerve – ophthalmic branch.

Question 37

What are the autonomic nerves that supply the eye?

Answer 37

Sympathetic: iris (dilator pupillae), ciliary body, lacrimal gland; parasympathetic: iris (sphincter pupillae), ciliary body, lacrimal gland.

Question 38

Name the bones that make up the bony orbit of the eye.

Answer 38

Ethmoid, sphenoid, maxilla, frontal, palatine, lacrimal, zygoma.

Question 39

What forms the roof of the orbit?

Answer 39

Orbital plate of the frontal bone and lesser wing of the sphenoid.

Question 40

What forms the medial wall of the orbit?

Answer 40

Orbital plate of ethmoid, maxilla, lacrimal, and body of the sphenoid.