topic 2 the eye

Question 1

outline the structure and function of the retina

Answer 1

● 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 2

What are cone cells?

Answer 2

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

Question 3

describe how dim light affects the size of the pupil

Answer 3

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

Question 4

What is accommodation?

Answer 4

the process by which the eye’s lens changes shape to focus near or far objects on the retina

Question 5

describe how the eye focuses on near objects

Answer 5

● 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 6

How is short-sightedness treated?

Answer 6

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

Question 7

How are cataracts treated?

Answer 7

The clouded lens is exchanged for a synthetic lens during surgery.

Question 8

identify the structures of the eye labelled in the diagram below

Answer 8

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

Question 9

outline the structure and the function of the cornea

Answer 9

transparent outer covering of the eye refracts light entering the eye

Question 10

outline the structure and function of the iris

Answer 10

● Pigmented ring of circular muscles and radial muscles

● Controls the size of the pupil to alter how much light enters the eye

Question 11

What is the pupil?

Answer 11

The hole in the iris center where light rays enter

Question 12

outline the structure and the function of the lens

Answer 12

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

Question 13

what is the function of the ciliary muscles and suspensory ligaments

Answer 13

To change the shape of the lens to allow light to focus on the retina

Question 14

What are rod cells?

Answer 14

Cells in the retina that are sensitive to low light intensity (dim light)

Question 15

what is the function of the optic nerve?

Answer 15

It transmits nerve impulses to the brain from the retina.

Question 16

describe how bright light affects the size of the pupil

Answer 16

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

Question 17

Why is the iris reflex important?

Answer 17

It prevents bright light from damaging the retina.

Question 18

Describe how the eye focuses on distant objects

Answer 18

● 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 19

What is long sightedness?

Answer 19

Can’t focus on near objects

Question 20

what are the causes of long sightedness

Answer 20

● 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 21

How is long-sightedness treated?

Answer 21

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

Question 22

What is short sightedness?

Answer 22

● Can focus on near objects clearly

● Cannot focus on distant objects

Question 23

what are the causes of short-sightedness?

Answer 23

● 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 24

What are cataracts?

Answer 24

clouding of the lens

Question 25

What is colour blindness?

Answer 25

● A deficiency 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