Visual defects in the eye

Question 1

What does accommodation mean?

Answer 1

• A reflex that changes the refractive power of the lens

Question 2

What is the shape of the lens controlled by?

Answer 2

• Suspensory ligaments
• Cilliary muscles

Question 3

How are the suspensory ligaments and cilliary muscles set up in the eye?

Answer 3

• The cilliary muscles form a ring surrounding the lens
• The suspensory ligaments connect the lens to the cilliary muscles

Question 4

What is the role of the lens and cornea?

Answer 4

• The cornea always refracts light by the same amount
• The lens fine-tunes the refraction so that the light perfectly hits the fovea

Question 5

What happens when we need to see close objects?

Answer 5

• Light needs to be refracted more so we need a short & fat lens (lens is more curved) for more powerful refraction
• The cilliary muscles will contract (towards the lens) and suspensory ligaments will slacken
• The lens will adopt its natural, fatter shape, making it more curved

Question 6

What happens when we need to see far objects?

Answer 6

• Light only needs to be refracted a bot
• Lens will need to be tall and thin (less curved)
• Cilliary muscles relex (outwards, away from les) and suspensory ligaments will be pulled taut

Question 7

What happens when someone is long-sighted?

Answer 7

• The lens can’t refract light enough so can’t see nearby objects
• Light gets focused behind the fovea
• Convex lens is used to refract light inwards
• Also known as hyperopia

Question 8

What happens when someone is short-sighted?

Answer 8

• The lens refracts ligh too much so can’t see far objects
• Light is focused before the fovea
• Concave lens is used to refract light outwards
• Also known as myopia