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PPO 1 > Introduction to Ametropia > Flashcards

Introduction to Ametropia Flashcards

1
Q

True or False: Ametropia is “the perfect eye”.

A

False. Emmetropia.

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2
Q

When an infinitely distant object is fixated on an Emmetropic eye, is the image sharply on the retina with or without accommodation?

A

Without accommodation.

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3
Q

What is Emmetropia?

A

The refractive condition in which parallel light rays are in focus exactly on the retina when the eye is at rest.

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4
Q

What type of refraction is Emmetropia measured by? What does the autorefractor read for Emmetropia?

A

Measured by a plano refraction. “0.00” diopter.

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5
Q

What is Ametropia?

A

The refractive condition in which, with accommodation relaxed, parallel light rays do not focus on the retina.

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6
Q

Name 3 examples of Ametropia.

A

Myopia, Hyperopia, Astigmatism.

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7
Q

In a myopic eye, do parallel light rays focus in front of the retina or behind?

A

In front.

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8
Q

How do you correct myopia?

A

Use minus lenses.

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9
Q

True or False: Myopia is when one cannot see well at distance.

A

True.

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10
Q

Why is myopia corrected with minus lenses?

A

Myopic eye means the eye is “too strong” (plus discrepancy). In order to relax this strength, minus lenses are used to decrease the strength and essential pull the image back to the retina.

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11
Q

In a hyperopic eye, do parallel light rays focus in front of the retina or behind?

A

Behind the retina.

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12
Q

How do you correct hyperopia?

A

Use plus lenses.

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13
Q

True or False: Hyperopia is when one cannot see well at distance.

A

False. Hyperopia is when on cannot see well at near.

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14
Q

Why is hyperopia corrected with plus lenses?

A

Hyperopic eye means the eye is “too weak” (minus discrepancy). In order to strengthen the power, plus lenses are used to essentially pull the image forward towards the retina.

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15
Q

What is astigmatism and how is it corrected?

A

When parallel light rays emanating from a single luminous point are not focused at a single point by an optical system. Cylinder lenses.

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16
Q

True or False: Astigmatism is when you cannot see at near or at distance.

A

True.

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17
Q

What are two reasons for myopia?

A

Steeper than normal corneal curvature or longer than normal axial length (bigger eye).

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18
Q

Myopia: Plus or minus. Diverge or converge. Concave or convex. Magnification or minification.

A

Minus, diverge, concave (like a timer), minification.

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19
Q

Hyperopia: Plus or minus. Diverge or converge. Concave or convex. Magnification or minification.

A

Plus, converge, convex (like a fish), magnification.

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20
Q

What’s low, moderate, and high amounts of myopia?

A

Low < -3.00D
Moderate > -3.00D to -6.00D
High > -6.00D

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21
Q

What are two reasons for hyperopia?

A

Flatter than normal corneal curvature or shorter than normal axial length (smaller eye)

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22
Q

What’s low, moderate, and high amounts of hyperopia?

A

Low < +2.00D
Moderate +2.25D to +5.00D
HIgh > +5.00D

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23
Q

Does accommodation increase or decrease the power of the eye?

A

Increase.

24
Q

When do we usually use accommodation? (In emmetropic eye)

A

At distance, it is at rest so no accommodation. Accommodation only occurs when trying to look at a near object or if an object is blurry.

25
Q

True or False: The emmetropic eye needs accommodation at distance.

A

False. At distance, accommodation is at rest.

26
Q

True or False: The emmetropic eye needs accommodation at near.

A

True. Accommodation is needed in order to increase its power to focus on an object at near.

27
Q

True or False: In a myopic eye, accommodation is needed in order to see near.

A

False. Accommodation is the process of increasing the power of the lenses. A myopic eye does not need accommodation because the eye is already too strong. Accommodation will only make the focusing worse.

28
Q

True or False: In a hyperopic eye, accommodation will help make vision clearer.

A

True. Hyperopic eyes are too weak. Any extra lens power will help strengthen the eyes to see clearer. Hyperopes can use accommodation to improve their distance vision.

29
Q

What is manifest hyperopia?

A

Hyperopia measured by relaxation of accommodation with the addition of plus lenses during the refraction. (Like plus lens test during vision screening).

30
Q

What is latent hyperopia?

A

Portion of the total hyperopia compensated for by the tonicity of the ciliary muscles. (usually revealed when ciliary muscles are paralyze for a brief moment with cycloplegic eye drops).

31
Q

What is total hyperopia?

A

The sum of the manifest and the latent hyperopia.

32
Q

What is facultative hyperopia?

A

Portion of the hyperopia that can be compensated for by accommodation. (hyperopes with accommodation at distance when emmetropes are at rest).

33
Q

True or False: Accommodation is limited.

A

True.

34
Q

Does accommodation increase as age increase?

A

No. Decreases.

35
Q

What is the amount of accommodation called?

A

Amplitude of accommodation.

36
Q

What is defined as a reduction in accommodative ability occurring normally with age.

A

Presbyopia.

37
Q

True or False: Presbyopia is an ametropia.

A

False. Presbyopia is an accommodation condition.

38
Q

What is defined as an unequal refractive state for the two eyes?

A

Anisometropia.

39
Q

True or False: Anisometropia is present if there is a difference in the refractive state between the two eyes of more than 1.00D.

A

True. Anything 2.00D or above is referred

40
Q

Give one example of a compound hyperopic anisometropia.

A

OD +1.00D and OS +3.00D. Both eyes are hyperopic.

41
Q

The example OD -1.00D and OS -3.00D is known as what type of anisometropia?

A

Compound myopic. Both eyes are myopic.

42
Q

True or False: Corneal curvature accounts for over 70% of anisometropia cases.

A

False. Axial length.

43
Q

What are some ocular signs of anisometropia?

A

Reduced depth perception and reduced vision in one eye.

44
Q

What are some symptoms of anisometropia?

A

headaches, eye strains (asthenopia), lack of depth perception.

45
Q

True or False: In astigmatism, rays are focused as two line images at different distances, usually at right angles from each other.

A

True.

46
Q

What two structures in the eye contribute to astigmatism?

A

Cornea and lens. (Both anterior and posterior surfaces).

47
Q

Different amounts of power existing around different regions of the eye that do not cause light rays to come to a single focus is known as what?

A

Astigmatism.

48
Q

<1.00D degree of astigmatism is low, moderate, high, or very high?

A

Low.

49
Q

1.00D to 3.00D degree of astigmatism is low, moderate, high, or very high?

A

Moderate.

50
Q

> 3.00D to 6.00D degree of astigmatism is low, moderate, high, or very high?

A

High.

51
Q

> 6.00D degree of astigmatism is low, moderate, high, or very high?

A

Very high.

52
Q

True or False: In a regular astigmatism, maximum and minimum refractive power meridians are separated by 180 degrees. It is not easily corrected.

A

False. 90 degrees. It is easily corrected by spectacle lens.

99% of the time will encounter these types of astigmatism patients

53
Q

True or False: In an irregular astigmatism, maximum and minimum refractive power meridians are separated by 90 degrees. It is easily corrected.

A

False. Other than 90 degrees. Not easily corrected by spectacle lens.

54
Q

What is irregular astigmatism associated with?

A

It is associated with pathology or prior ocular surgery.

55
Q

There is a way irregular astigmatism can be easily treated. What way is that and in what condition?

A

Easily corrected by a rigid contact lens only if corneal.

56
Q

What is the purpose of the autorefractor?

A

Gives an estimate of the refractive error in the OD and OS eye.

PPO 1 (7 decks)

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