The Eye

Question 1

Focusing on Near Objects

Answer 1

• ciliary muscles contract
• suspensory ligaments slacken
• lens fattens/curves
• refracts light more strongly

Question 2

Focusing on Distant Objects

Answer 2

• ciliary muscles relax
• suspensory ligaments pulled taut
• lens thins
• light refracted less

Question 3

Long-Sightedness

Answer 3

Hyperopia
- can’t refract light enough/eyeball is too short
- unable to focus near objects
- image appears behind retina
- object appears blurry

Question 4

Correcting long-sightedness

Answer 4

Convex lens
- increases refraction power
- to focus light on retina

Question 5

Short-sightedness

Answer 5

Myopia
- lens is wrong shape so it refracts light too much/eyeball is too long
- image formed before the retina
- object appears blurry

Question 6

Correcting short-sightedness

Answer 6

Concave lens
- refracts light outwards
- counteracts over-refraction of lens
- allows light to focus on retina

Question 7

Retina

Answer 7

• contains cone receptor cells, sensitive to colour
• contains rod receptor cells, sensitive to light

Question 8

Iris reflex

Answer 8

• controls size of pupil
• prevents damage to retina from bright light
• smaller pupil in bright light
• larger pupil in low light

Question 9

Pupil constriction

Answer 9

• circular muscles constrict
• radial muscles relax
• pupil shape becomes smaller to let in less light

Question 10

Pupil dilation

Answer 10

• circular muscles relax
• radial muscles contract
• pupil shape becomes larger to let in more light

Question 11

Sclera

Answer 11

• tough supporting wall of the eye

Question 12

Optic nerve

Answer 12

• carries impulses from receptors on the retina to the brain

Question 13

Cornea

Answer 13

• transparent outer layer at the front of the eye, refracts light into the eye

Question 14

Iris

Answer 14

• contains muscles that control diameter of the pupil

Question 15

Laser Eye surgery

Answer 15

• laser vaporises cornea, changing the shape of the cornea
  -> sliming lens, weakening strength -> improves myopia
  -> changing shape, increases strength -> improves hyperopia
• risk of infection

Question 16

Contact lenses

Answer 16

• thin lenses sit on eye’s surface to compensate faults in focusing
• lightweight/almost invisible
• convenient
• hard/soft lenses exist
  -> soft, more comfortable, but higher risk of infection

Question 17

Replacement lens surgery

Answer 17

• treats hyperopia
• natural lens replaced with artificial lens made of clear plastic
• higher risk than laser surgery
• possible retina damage