The eye Flashcards

1
Q

what does the cornea do

A

it starts focussing the light rays

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2
Q

what does the iris do

A

Coloured part, which controls the size of the pupils

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3
Q

what do lens do

A

focus light rays onto the back of the eye
- can change shape allowing us to focus on distant or near objects

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4
Q

what does the retina do

A

contains the light receptors, allows us to detect light intensity and colour

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5
Q

what does the optic nerve do

A

carries impulses between the eye and brain

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6
Q

what does the sclera do

A

white part of the eye that protects the eye

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7
Q

what do sensory ligaments and ciliary muscles do

A

allow us to focus on distant and near objects

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8
Q

what happens to pupils in dim light

A

1 - radical muscles of iris CONTRACT
2 - circular muscle of iris RELAXED
3- pupil becomes more dilated, so more light enters the eye

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9
Q

what happens to pupils in bright light

A
  1. radical muscles of iris RELAX
  2. circular muscles of iris CONTRACT
  3. pupil contracts, so less light enters the eye and protects it from damage
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10
Q

what is accomodation

A

the process of changing the shape of the lens to focus on near or distant objects.

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11
Q

what happens when our eye focuses on a near object

A
  • the ciliary muscle muscle contracts, the suspensory ligaments loosen, making the lens thicker and able to refract light rays more strongly
  • light rays also focused on a point on the retina
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12
Q

what happens when our eye focuses on a distant object

A
  • the ciliary muscle relaxes
  • suspensory ligaments are pulled tight
  • lens pull thin and only slightly refract light rays
  • light rays are now focused to a point on the retina
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13
Q

what causes short sightedness and what happens when someone has it

A
  • eyeball being too long, so light is focused at a point infront of the retina
  • or lens being the wrong shape (too thick)
  • they can only see things close up
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14
Q

how to treat short sightedness

A

treated using concave lens which partially unfocus light before it enters the eye

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15
Q

what causes long sightedness and what happens when someone has it

A
  • eyeball is too short so light is focused at a point BEHIND the retina
  • so they can only see things from far away clearly
  • a loss of elasticity in the lens - meaning it cannot become thick enough to focus
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16
Q

how to treat long- sightedness

A

treated using convex lens which partially focus the ight before it enters the eye

17
Q

biology word for long sightedness

A

hyperopia

18
Q

biology word for short sightedness

A

myopia

19
Q

what does laser surgery do

A

changes the shape of the cornea so that it refracts light to a greater or lesser extent

20
Q

how do contact lenses work

A

They float on the surface of the cornea. They work like glassses,by focusing and refracting the light.

21
Q

how do replacement lens work

A

implanting artificial lens, and placing them in front of original lens through a small cut in the cornea

22
Q

to focus on near objects, the lens become

A

thicker

23
Q

to focus on distant objects, the lens become

A

thinner

24
Q

what is the eye and what does it do

A

a sense organ which contains receptors sensitive to light intensity and colour

25
Q

what is the pupil

A
  • the space in the centre of the iris which light passes through
26
Q

what does the ciliary muscle do

A

changes the thickness of the lens