Eye defects

Question 1

Pupil?

Answer 1

Centre of the iris, it varies in size to regulate the amount of light that reaches the retina

Question 2

Iris

Answer 2

Made up of muscles called circular and radial muscles that work antagonistically to regulate the size of the pupil

Question 3

Reflex response to dim light

Answer 3

Circular muscles relax, radial muscles contract, pupil dilates so that more light can enter the eye

Question 4

Reflex response to bright light

Answer 4

Circular muscles contract, radial muscles relax, pupil constricts so that less light can enter the eye

Question 5

Cornea

Answer 5

Focuses the entry of light into the eye but is fixed and unable to adjust its focus

Question 6

Lens

Answer 6

Focuses light rays to the back of the eye and can change shape to adjust focus for distant and near objects

Question 7

Retina

Answer 7

The light-sensitive surface at the back of the eye containing receptor cells that detect light

Question 8

Accommodation

Answer 8

The process by which the eye lens changes shape to focus on near or distant objects

Question 9

Ciliary muscles

Answer 9

Works with the suspensory ligaments and can contract or relax to adjust the shape of the lens

Question 10

Suspensory ligaments

Answer 10

Works with the ciliary muscles and can loosen or be pulled tight to adjust the shape of the lens

Question 11

Focusing on a near object

Answer 11

Ciliary muscles contract, suspensory ligaments loosen, lens is thicker and refracts light rays strongly

Question 12

Focusing on a distant object

Answer 12

Ciliary muscles relax, suspensory ligaments pull tight, lens is pulled thin and only slightly refracts light rays

Question 13

Hyperopia (long-sightedness)

Answer 13

Where a person has difficulty focusing on nearby objects because the light rays focus behind the retina

Question 14

Causes of hyperopia

Answer 14

When the lens is too weak or the eyeball is too short

Question 15

Myopia (short-sightedness)

Answer 15

Where a person has difficulty focusing on distant objects because the light rays focus in front of the retina

Question 16

Causes of myopia

Answer 16

When the lens is too strong or eyeball is too long

Question 17

Convex lenses

Answer 17

Used for correcting hyperopia by moving an image forward and focusing it on the retina

Question 18

Concave lenses

Answer 18

Used for correcting myopia by moving an image further back and focusing it on the retina

Question 19

Modern sight treatments

Answer 19

Hard and soft contact lenses, laser surgery and lens replacement

Question 20

Colour blindness

Answer 20

An abnormal genetic condition that is characterised by the inability to clearly distinguish different colours of the visible light spectrum, as a result of deformed or altered cone cells

Question 21

Cataracts

Answer 21

Clouding of the lens which can obscure vision, corrected via artificial lens replacement