Eye and Vision Physiology

Question 1

What are the three coats of the eye, from superficial to deep?

Answer 1

The fibrous coat, vascular coat and the sensory coat

Question 2

What are the component parts of the fibrous coat of the eye?

Answer 2

The cornea and the sclera

Question 3

What are the component parts of the vascular coat of the eye?

Answer 3

The iris, ciliary body and the choroid

Question 4

What are the component parts of the sensory coat of the eye?

Answer 4

The retina

Question 5

Which coats of the eye are complete and incomplete?

Answer 5

Complete- fibrous

Incomplete- vascular and sensory

Question 6

What structure does the anterior segment of the eye lie anterior to, and what is it filled with?

Answer 6

The lens

Filled with aqueous humor

Question 7

What structure does the posterior segment of the eye lie posterior to, and what is it filled with?

Answer 7

The lens

Filled with vitreous humor

Question 8

In what segment of the eye are the anterior and posterior chambers found, and what structure divides them?

Answer 8

Both found in anterior segment

Divided by iris

Question 9

Describe the drainage of the aqueous humor

Answer 9

The aqueous humor first drains to the trabecular meshwork in the angle of the anterior chamber, which drains to Schlemm’s canal, which drains to veins

Question 10

Name the quadrants of the eye

Answer 10

The upper nasal, lower nasal, upper temporal and lower temporal quadrants

Question 11

What kind of epithelium is present in the cornea?

Answer 11

Stratified, squamous, non-keratinised epithelium

Question 12

What is the basement membrane of the corneal epithelium called?

Answer 12

Bowman’s membrane

Question 13

How is transparency of the cornea maintained, histologically?

Answer 13

Regular arrangement of collagen
No blood vessels
Endothelial layer has a pump that keeps the aqueous humor out

Question 14

What is the site of most visual acuity in the eye called?

Answer 14

The fovea centralis

Question 15

What are the functions of the tear film?

Answer 15

Keeps cornea moist
Prevents drying
Washes away any particulate foreign bodies
Has antibodies and lysozymes to kill microbes
Smooths outer surface of cornea providing smooth surface for refraction.

Question 16

What nerve controls secretion of tears into the conjuctival sac?

Answer 16

Parasympathetic fibres of the facial nerve

Question 17

What structures of the eye are responsible for refraction of light?

Answer 17

The cornea, aqueous humor and the lens

Question 18

What is the visual field?

Answer 18

Everything that you can see with one eye (including periphery)

Question 19

Where do the nasal fibres of the optic nerve cross over?

Answer 19

At the optic chiasma

Question 20

Which fibres of the optic nerve cross over at the optic chiasma?

Answer 20

The nasal fibres

Question 21

Where do fibres from the optic tract synapse?

Answer 21

The lateral geniculate body of the thalamus

Question 22

Which half of the visual cortex sees which half of the visual field?

Answer 22

The right half of the visual cortex sees the left half of the visual field and vice versa

Question 23

What damage would be expected if one of the optic nerves is damaged?

Answer 23

Blindness in the ipsilateral eye

Question 24

What damage would be expected if the optic chiasma is disrupted in the middle?

Answer 24

Bitemporal hemianopia

Question 25

What damage would be expected if one of the optic tracts is damaged?

Answer 25

Contralateral homonymous hemianopia

Question 26

What damage would be expected if optic radiation is damaged?

Answer 26

Contralateral homonymous hemianopia

Question 27

What is the action of the intrinsic muscles of the eye as a group?

Answer 27

Control pupil diameter and alter lens curvature

Question 28

What is the action of the extrinsic muscles of the eye as a group?

Answer 28

Movement of the eye

Question 29

What are the names of the six extrinsic occular muscles?

Answer 29

``` Superior rectus Inferior rectus Lateral rectus Medial rectus Superior oblique Inferior oblique ```

Question 30

Describe the innervation of the extrinsic muscles of the eye

Answer 30

Superior oblique- trochlear nerve Lateral rectus- abducent nerve All others- occulomotor nerve

Question 31

What are the names of the intrinsic muscles of the eye?

Answer 31

Ciliaris Constrictor pupillae Dilator pupillae

Question 32

Describe the transduction mechanism involved in vision

Answer 32

Trans-retinol is converted into cis-retinol in the retinal pigment epithelium, using up some vitamin A. Cis-retinol is then transported back to the rods and cones to form opsin. The cascade of reactions within the rods/cones causes a hyperpolarisation, which transmits an impulse and becomes an action potential in the optic nerve cell

Question 33

What is the conjuctiva?

Answer 33

A thin, vascular membrane that covers the inner surface of the eyelids and the sclera

Question 34

What is the cornea?

Answer 34

It is the anterior 1/6th of the fibrous coat of the eyeball, it is transparent and allows light rays to enter the eyeball

Question 35

What is the sclera?

Answer 35

The posterior 5/6s of fibrous coat, opaque and gives attachments to muscles but does not move the eye

Question 36

What is the function of the ciliary body?

Answer 36

Suspends the lens and produces aqueous humor

Question 37

What is the function of the choroid?

Answer 37

Supplies blood to out layers of retina

Question 38

What is the function of the iris?

Answer 38

Controls the diameter of the pupil

Question 39

Is the crystalline lens biconvex or biconcave?

Answer 39

Biconvex

Question 40

How is the crystalline lens connected to the ciliary body?

Answer 40

Through suspensory ligaments

Question 41

What is the function of the aqueous and vitreous humors?

Answer 41

Aqueous- helps maintain intraocular pressure | Vitreous- Cushions the retina

Question 42

How is the lacrimal gland innervated?

Answer 42

It receives parasympathetic innervation from the facial nerve

Question 43

Where do the lacrimal ducts open into?

Answer 43

The conjuctival sac

Question 44

How do tears drain from the eyes?

Answer 44

Through punctae on the medial sides of the eyelids, draining into the lacrimal sac, which drains to the nasolacrimal duct, which drains into the inferior meatus

Question 45

Describe the innervation of the intrinsic muslces of the eye

Answer 45

Ciliaris and constrictor pupillae- parasympathetic from third nerve Dilator pupillae- sympathetic from plexus around blood vessels

Question 46

What artery supplies all the structures within the orbit?

Answer 46

The ophthalmic artery

Question 47

What veins drain the eye, and what do they drain into?

Answer 47

The superior and inferior ophthalmic veins, which drain into the cavernous sinus