The Eye

Question 1

Identify the structures of the eye

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Answer 1

A= cornea
B = iris
C = ciliary muscle
D = lens
E = suspensory ligaments
F = retina
G = optic nerve

Question 2

Outline the structure and function of the cornea

Answer 2

● Transparent outer covering of the eye

● Refracts light entering the eye

Question 3

Outline the structure and function of the iris

Answer 3

● Pigmented ring of circular muscles and
radial muscles
● Controls the size of the pupil to alter how
much light enters the eye

Question 4

What is the pupil?

Answer 4

Ahole in the iris centre that allows light

rays to enter the eye

Question 5

Outline the structure and function of the lens

Answer 5

● Transparent, bi-convex structure
● Suspensory ligaments attach the lens to a ring
of ciliary muscle
● Refracts light, focusing it onto the retina

Question 6

What is the function of the ciliary muscles and

suspensory ligaments?

Answer 6

Change the shape of the lens (accomodation)

to focus light onto the retina

Question 7

Outline the structure and function of the retina

Answer 7

● Light sensitive layer composed of rod and
cone cells
● Converts light energy into neural signals which
are sent to the brain via the optic nerve

Question 8

What are rod cells?

Answer 8

Cells in the retina that are sensitive to

low light intensity (dim light)

Question 9

What are cone cells?

Answer 9

Cells found in the retina that are sensitive
to high light intensity (bright light) and can
detect different colours.

Question 10

What is the function of the optic nerve?

Answer 10

It transmits nerve impulses to the brain

from the retina.

Question 11

Describe how dim light affects the size of the pupil

Answer 11

● Light receptors detect dim light
● Circular muscles relax
● Radial muscles contract
● Pupil dilates
● More light enters the pupil

Question 12

Describe how bright light affects the size of the pupil

Answer 12

● Light receptors detect bright light
● Circular muscles contract
● Radial muscles relax
● Pupil contracts
● Less light enters the pupil

Question 13

Why is the iris reflex important?

Answer 13

It prevents bright light from damaging the

retina.

Question 14

What is accommodation?

Answer 14

● Process by which the elastic lens changes its shape
(with the aid of ciliary muscles and suspensory
ligaments) to focus on near or distant objects
● Light is focused onto the retina

Question 15

Describe how the eye focuses on near objects

Answer 15

● Near object
● Ciliary muscles contract
● Suspensory ligaments slacken
● Lens becomes more convex (more rounded)
● Light is refracted more
● Light rays focused onto the retina

Question 16

Describe how the eye focuses on distant objects

Answer 16

● Distant object
● Ciliary muscles relax
● Suspensory ligaments tighten
● Lens becomes less convex (less rounded)
● Light is refracted less
● Light rays focused onto the retina

Question 17

What is long-sightedness?

Answer 17

● Can focus on distant objects clearly

● Cannot focus on near objects

Question 18

What are the causes of long-sightedness?

Answer 18

● Eyeball is too short
● Lens is less elastic (usually age-related)
● ∴ light rays are not focussed onto the retina,
instead converging behind the retina

Question 19

How is long-sightedness treated?

Answer 19

● Using a convex lens (causes light rays to
converge) in glasses or contact lenses
● Replacement lenses
● Laser eye surgery

Question 20

What is short-sightedness?

Answer 20

● Can focus on near objects clearly

● Cannot focus on distant objects

Question 21

What are the causes of short-sightedness?

Answer 21

● Eyeball is too long
● Lens is too thick and too rounded
● ∴ light rays are not focussed onto the retina,
instead converging in front of the retina

Question 22

How is short-sightedness treated?

Answer 22

● Using a concave lens (causes light rays
to diverge) in glasses or contact lenses
● Replacement lenses
● Laser eye surgery

Question 23

What are cataracts?

Answer 23

● Acloudy patch forms on the lens of the eye
which negatively affects vision
● Vision becomes blurry, difficult to see the
intensity of colours, problems with glare etc.

Question 24

How are cataracts treated?

Answer 24

The clouded lens is exchanged for a

synthetic lens during surgery.

Question 25

What is colour-blindness?

Answer 25

● Adeficiency of the eye that makes it difficult to
distinguish between colours
● e.g. individuals with red-green colour blindness have
difficulty differentiating between red and green

Question 26

What is the cause of colour-blindness?

Answer 26

Damage to cone cells in the retina