Ocular Structures

Question 1

Cornea

Answer 1

transparent, connective tissue membrane

set into the sclera

Question 2

Average diameter of Cornea

Answer 2

Vertical 11.5mm

Horizontal 12.0mm

Question 3

Average thickness of the Cornea at the limbus

Answer 3

0.7-0.9mm

Question 4

How many layers make up the Cornea?

Answer 4

5
Epithelium 
Bowman'membrane 
Stroma
Descemet's membrane
Endothelium

Question 5

Where does the Cornea receive its nourishment from?

Answer 5

Tear film that covers and the aqueous humor that flows beneath it.
The cornea has no blood vessels.

Question 6

What is the junction between the sclera and cornea called?

Answer 6

Limbus

Question 7

What is the main function of the cornea?

Answer 7

To focus light rays reflected to the eye

Question 8

Pars Plana

Answer 8

external periphery of the retina

Question 9

Zonule Fibers

Answer 9

resemble fibers of a spider’s web spread out between the ciliary body and the crystalline lens and fix the crystalline lens in a central position - behind the iris and the pupil.

Question 10

Pupil

Answer 10

circular opening in the center of the iris.

the eye can adapt rapidly to changes in light by opening and closing the pupil.

Question 11

Sclera

Answer 11

white outer layer of the eye
stabilizes the eye
starts at the front edge of the limbus and covers the eye to the posterior optic nerves

Question 12

What does the Sclera comprise of?

Answer 12

dense, white fibrous tissue

Question 13

What is the main function of the Sclera?

Answer 13

to protect the contents of eyeball.

it also helps to prevent the scattering of light rays

Question 14

What are the six extra-ocular muscles that have their insertions on the sclera?

Answer 14

Lateral Rectus (LR)
Medial Rectus (MR)
Superior Rectus (SR)
Inferior Rectus (IR)
Superior Oblique (SO)
Inferior Oblique (IO)

Question 15

Conjunctiva

Answer 15

thin, translucent mucous membrane that lines the inner surface of the top and bottom eyelids and the outer surface of the eyeball except for the cornea.

Question 16

What helps the eyelids to slide easily against the outer surface of the eyelid?

Answer 16

the slippery nature of the conjunctival tissue and the folds in the fornix

Question 17

Limbus

Answer 17

the transition from the transparent cornea to the white opaque sclera

Question 18

Iris

Answer 18

comparable to the aperture of a camera
coloured part of the eye
situated behind the cornea and in front of the lens

Question 19

Eye colour is determined by?

Answer 19

the number of brown pigment cells on its surface - blue eyes have very few pigment cells

Question 20

Two Iris muscles

Answer 20

the actions of the muscles are either to contract or dilate the pupil, controlling the amount of light entering the inner part of the eye.

Question 21

sphincter muscle

Answer 21

the circular muscle in the iris that constricts the pupil.

parasympathetic nerve activity that normally innervates this muscle.

Question 22

dilator muscle

Answer 22

the radial muscle in the iris that dilates the pupil

sympathetic nerve activity that normally innervates this muscle.

Question 23

What divides the anterior and posterior chambers of the eye?

Answer 23

the iris

Question 24

What do both the anterior and posterior chambers of the eye contain?

Answer 24

aqueous humour

Question 25

Retina

Answer 25

sticks like wallpaper to the posterior eyeball.

it is the light sensitive part of the eye and is comparable to the film of a camera.

Question 26

what is at the center of the retina?

Answer 26

macula

Question 27

what does retinal thickness vary between?

Answer 27

0.1 and 0.5mm

Question 28

Optic nerve head

Answer 28

optic nerve runs from the optic nerve head to the visual centre in the brain.
it consists of approx 1 million nerve fibres

Question 29

Macula

Answer 29

area at the center of the retina- important for focuse vision and reading

Question 30

Diameter of the macula?

Answer 30

approx 5.5mm

Question 31

Diameter of the optic nerve?

Answer 31

3 and 4mm

Question 32

Crystalline lens

Answer 32

directly behind the iris

it bundles the light falling in through the pupil and generates an image on the retina.

Question 33

Ciliary body

Answer 33

continuous with the root of the iris and is mainly muscle fibres.
production of aqueous humor and for accomadation

Question 34

accomadation

Answer 34

when the ciliary muscle contracts, causing a change in the curvature of the crystalline lens. This is how the eye adjusts itself to focus on near or distant objects.

Question 35

where do the suspensory ligaments have their insertions?

Answer 35

the ciliary body

Question 36

What does contraction/ relaxation of the suspensory ligaments do?

Answer 36

alter the shape of the lens

Question 37

what is produced by the ciliary processes?

Answer 37

aqueous humour

Question 38

aqueous humour

Answer 38

provides nourishment for intraocluar structures and also helps to maintain the intraocular pressure at an average of 15mmHg in the adult eye

Question 39

lower fornix

Answer 39

fornix is an anatomical structure that is arched or vault like.
when either lower lids are gently pulled down it exposes a loose pocket of conjunctival tissue - the fornix.
the lower fornix can be used as an excellent trap for drops and ointments as well as material such as debris and foreign matter.