B17c Eyes (triple only)

Question 1

Name the process used to focus light from near and far objects

Answer 1

Accommodation

Question 2

What stimuli are the receptors of the eye sensitive to?

Answer 2

Light intensity

Colour

Question 3

What are the 2 main functions of structures found within the eye?

Answer 3

Accommodation

Adaptation to dim light

Question 4

Describe the structure and function of the retina

Answer 4

Found at the back of the eye
Contain light sensitive cells (rods and cones)
Light sensitive cells send impulses to the brain

Question 5

Describe the structure and function of the optic nerve

Answer 5

Optic nerve connects the eye and the brain
Contains sensory neurones
Send electrical impulses from the retina to the brain

Question 6

Describe the structure and function of the sclera

Answer 6

Tough outer layer of the eye

Protects internal structures

Question 7

Describe the structure and function of the cornea

Answer 7

Curved transparent layer at the front of the eye
Lets light into the eye
Allows light to be focussed on the retina

Question 8

Describe the structure and function of the iris

Answer 8

Iris is a muscle
Controls the size of the pupil by contracting and relaxing the muscles
Allows the eye to adjust to bright and dim light

Question 9

Describe the structure and function of the ciliary muscles and suspensory ligaments

Answer 9

Hold the lens in place

Can change the shape of the lens

Question 10

Describe how the iris alters the size of the pupil in bright light

Answer 10

Circular muscle contract
Radial muscles relax
makes pupil smaller to avoid damage to retina

Question 11

Describe how the iris alters the size of the pupil in dim light

Answer 11

Circular muscles relax
Radial muscles contract
Makes pupil larger so more light can enter the eye

Question 12

How does the eye focus on a close object?

Answer 12

Ciliary muscle contract
Suspensory ligaments loosen
Lens becomes thicker and more curved
Light is refracted strongly
Image forms on the retina

Question 13

How does the eye focus on distant objects?

Answer 13

Ciliary muscles relax
Suspensory ligaments tighten
Lens is puller thinner 
Light is refracted less strongly
Image falls on the retina

Question 14

What is myopia?

Answer 14

Short-sightedness
Lens becomes too curved
Light is focused in front of the retina
Images appear blurry

Question 15

How can myopia be treated?

Answer 15

Using glasses or contact lenses
Concave lens
Spreads the light so they can be focused on the retina

Question 16

What is hyperopia?

Answer 16

Long-sightedness
Lens is too flat
Light is focused behind the retina
Images appear blurry

Question 17

How can hyperopia be treated?

Answer 17

Using glasses or contact lenses
Convex lens
Brings light rays together
Image formed on the retina

Question 18

What is laser eye surgery?

Answer 18

Use lasers to fix visual defects n adults
Myopia - laser reduces the thickened of the cornea so light is refracted less strongly
Hyperopia - laser alters curvature of the cornea so light is refracted correctly

Question 19

How can replacement lenses by used to treat visual defects?

Answer 19

Replacement lens replaces the natural lens

Question 20

What are the risks of lens replacement?

Answer 20

Can cause retinal damage, cataracts and infections