B10.5 AND B10.6 - The eye

Question 1

What is the function of the SCLERA?

Answer 1

Sclera is the tough supporting wall of the eye

Question 2

What is the function of the CORNEA?

Answer 2

Cornea is the transparent outer layer found at the front of the eye, refracts light into the eye

Question 3

What is the function of the IRIS?

Answer 3

Contains muscle that control diameter of pupil determining how much light enters

Question 4

What is the function of the LENS?

Answer 4

Focuses light on the retina (contains receptor cells sensitive to light and colour

Question 5

What is the function of the CILIARY MUSCLE AND SUSPENSORY LIGAMENTS

Answer 5

holds and controls shape on lens to fine focus light on the retina

Question 6

What is the function of the OPTIC NERVE

Answer 6

carries impulses from receptor on retina to brain

Question 7

What does the iris reflex do?

Answer 7

Bright light can damage the retina

• light receptor detects and reflex triggered to make pupil SMALLER (constricts)
• circular muscles in iris contract and radial muscles relax reducing amount of light entering
• dim light it is the opposite (circular relax and radial contract) = dilates

Question 8

How does a light ray entering the eye translate to a visual image in the brain?

Answer 8

An image falls on the back of the retina and impulses are sent through the optic nerve to the brain

Question 9

ACCOMODATION - What happens when you look at near objects?

Answer 9

• Cilliary muscles contract
• suspensory ligaments loosen
• lens become thicker and curved
• refracts light rays more and stronger

Question 10

ACCOMODATION - What happens when you look at distant objects?

Answer 10

• cilliary muscles relax
• suspensory ligaments tighten
• lens is pulled flat and thin
• refract light rays slightly

Question 11

MYOPIA - short sightedness

Answer 11

unable to focus on distant objects, light is focused infront of retina so images landing on retina are blurred
- result of a lense too curved and refract too much light
- long eyeball
use glasses with a concave lens (curves inwards) spread out light from distant objects and bring focus to retina

Question 12

HYPEROPIA - long sightedness

Answer 12

• lens is too flat and thin so doesnt refract the light
• short eyeball
  light is focused behind the retina
  use glasses with a convex lens to refract light

Question 13

Contact lenses

Answer 13

thin lenses sit on the surface of eye and shaped to compensate, lightweight and invisible

• hard lenses = last long time but must remove and put be put in sterile conditions
• soft lenses = comfortable but more risk of eye infection

Question 14

Laser eye surgery

Answer 14

vaporise tissue changing the shape of cornea, only available to adults were eyesight is not growing
myopia = reduce thickness of cornea#
- can be precisely corrected
- infections or worse vision

Question 15

Replacement lens surgery

Answer 15

Natural lens removed and artificial lens inserted

• works inside eye so higher risk
• possible damage to retina can lead to loss in vision