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Ophthalmology > 3: Refractive Errors > Flashcards

3: Refractive Errors Flashcards

1
Q

What is a refractive error

A

Failure of the eye to focus light from objects onto the retina to obtain a clear image

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2
Q

What is a refractive error

A

Failure of the eye to focus light from objects onto the retina to obtain a clear image

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3
Q

Why do refractive errors occur

A

Defect in size or shape of the eye

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4
Q

What is ametropia

A

refractive error on looking at distant objects

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5
Q

What is myopia

A

short-sightedness. Image is brought to focus in-front of the retina

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6
Q

What is hypermetropia

A

long-sightedness: image is brought to focus behind the retina

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7
Q

What is astigmatism

A

optical powers are unequal across different meridians

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8
Q

What is presbyopia

A

eye focus range is reduced with age

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9
Q

What is emmetropia

A

no refractive error when looking at distant objects

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10
Q

what is myopia

A

short-sightedness

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11
Q

pathophysiologically what happens in myopia

A

light refracts before the retina

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12
Q

what causes myopia

A
  • Refractive power of the lens is too strong

- AP diameter of the eye is too large

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13
Q

what Is index myopia

A

Refractive power of the lens is too strong

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14
Q

how will individual in short-sightedness present clinically

A

Viewing far away objects is impaired, but close objects is normal.

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15
Q

what is first-line for myopia

A

Corrective lenses

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16
Q

what corrective lens is used for myopia and why

A

Negative lenses as they cause diffraction of the light before the eye refracts it. Meaning light converges on the retina instead of in-front of it

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17
Q

what surgical procedure may be used for myopia

A

LASIK (Laser assisted in situ keratomileusis)

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18
Q

what does myopia increase the risk of

A

Open-angle glaucoma
Retinal detachment
Vitreous detachment

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19
Q

what is hypermetropia

A

long-sightedness

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20
Q

what causes hypermetropia

A

weak lens

short AP diameter

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21
Q

Explain pathophysiology of hypermetropia

A

Light converges behind the retina. To compensate the ciliary muscles contract to try and increase thickness of the lens. This leads to squint in children and tiredness of gaze (headaches, ocular fatigue)

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22
Q

What is first line for hypermetropia

A

Corrective lenses

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23
Q

What type of corrective lenses are used in hypermetropia and why

A

Positive - to increase convergence so they converge before retina

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24
Q

What is second-line for hypermetropia

A

LASIK

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25
Q

What does hypermetropia increase risk of

A

close-angle glaucoma

26
Q

What is astigmatism

A

Refracting power of the eye differs between meridians

27
Q

How will astigmatism present

A

Blurry vision regardless of depth

28
Q

When does astigmatism occur

A

Cornea does not have the same degree of curvature in each eye. Meaning when light rays are focused they do not come together in the same point.

29
Q

If a regular astigmatism what lenses are required

A

Cylindrical

30
Q

what is a risk of early-onset astigmatism

A

amblyopia

31
Q

what is presbyopia

A

with age tension in ciliary muscles decreases causing lens to become more convex for close focusing

32
Q

how does presbyopia present

A

difficultly with focusing

33
Q

Why do refractive errors occur

A

Defect in size or shape of the eye

34
Q

What is ametropia

A

refractive error on looking at distant objects

35
Q

What is myopia

A

short-sightedness. Image is brought to focus in-front of the retina

36
Q

What is hypermetropia

A

long-sightedness: image is brought to focus behind the retina

37
Q

What is astigmatism

A

optical powers are unequal across different meridians

38
Q

What is presbyopia

A

eye focus range is reduced with age

39
Q

What is emmetropia

A

no refractive error when looking at distant objects

40
Q

what is myopia

A

short-sightedness

41
Q

pathophysiologically what happens in myopia

A

light refracts before the retina

42
Q

what causes myopia

A
  • Refractive power of the lens is too strong

- AP diameter of the eye is too large

43
Q

what Is index myopia

A

Refractive power of the lens is too strong

44
Q

how will individual in short-sightedness present clinically

A

Viewing far away objects is impaired, but close objects is normal.

45
Q

what is first-line for myopia

A

Corrective lenses

46
Q

what corrective lens is used for myopia and why

A

Negative lenses as they cause diffraction of the light before the eye refracts it. Meaning light converges on the retina instead of in-front of it

47
Q

what surgical procedure may be used for myopia

A

LASIK (Laser assisted in situ keratomileusis)

48
Q

what does myopia increase the risk of

A

Open-angle glaucoma
Retinal detachment
Vitreous detachment

49
Q

what is hypermetropia

A

long-sightedness

50
Q

what causes hypermetropia

A

weak lens

short AP diameter

51
Q

Explain pathophysiology of hypermetropia

A

Light converges behind the retina. To compensate the ciliary muscles contract to try and increase thickness of the lens. This leads to squint in children and tiredness of gaze (headaches, ocular fatigue)

52
Q

What is first line for hypermetropia

A

Corrective lenses

53
Q

What type of corrective lenses are used in hypermetropia and why

A

Positive - to increase convergence so they converge before retina

54
Q

What is second-line for hypermetropia

A

LASIK

55
Q

What does hypermetropia increase risk of

A

close-angle glaucoma

56
Q

What is astigmatism

A

Refracting power of the eye differs between meridians

57
Q

How will astigmatism present

A

Blurry vision regardless of depth

58
Q

When does astigmatism occur

A

Cornea does not have the same degree of curvature in each eye. Meaning when light rays are focused they do not come together in the same point.

59
Q

If a regular astigmatism what lenses are required

A

Cylindrical

60
Q

what is a risk of early-onset astigmatism

A

amblyopia

61
Q

what is presbyopia

A

with age tension in ciliary muscles decreases causing lens to become more convex for close focusing

62
Q

how does presbyopia present

A

difficultly with focusing

Ophthalmology (12 decks)

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