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II. Ophthalmic Optics > Midterm II > Flashcards

Midterm II Flashcards

1
Q

When are refractive errors considered as combinations of refractive and axial issues?

A
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2
Q

When are refractive errors considered as almost completely axial in nature?

A

> +/-4.00D

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3
Q

What is the dioptric difference between the far and near points of accommodation called?

A

amplitude of accommodation

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4
Q

Is the amplitude of accommodation underestimated or overestimated for a hyperope?

A

underestimated

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5
Q

When hyperopes wear contact lenses do they accommodate more or less than without?

A

less

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6
Q

Is the amplitude of accommodation underestimated or overestimated for a myope?

A

overestimated

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7
Q

Will myopes or hyperopes require presbyopic correction earlier?

A

hyperopes

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8
Q

Does an aphakic patient have an increased of decreased peripheral field of view? 1. macular FOV? 2

A
  1. decreased

2. decreased

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9
Q

When hyperopes wear contact lenses do they accommodate more or less than without?

A

less

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10
Q

What happens to the scotoma size for each of the following:

  1. increase lens power
  2. inc vertex distance
  3. inc lens size
  4. dec pupils size
  5. inc lens thickness
  6. inc base curve
A
  1. increase scotoma size
  2. dec scotoma size
  3. inc scotoma size
  4. inc scotoma size
  5. inc scotoma size
  6. inc scotoma size
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11
Q

What is the field of view for the moving eye, subtended at the center of rotation?

A

macular field of view

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12
Q

What is larger, the macular field of view or the peripheral field of view?

A

peripheral field of view

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13
Q

What is the prismatic effect that a high plus lens creates, having an angular gap in object space completely around the lens?

A

ring scotoma

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14
Q

What is the work eyes will have to do to see a single image (demand for fusional vergence)?

A

phoria

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15
Q

What kind of distortion do aphakic spectacle wearers experience?

A

pincushion distortion

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16
Q

What kind of distortion do high myopic spectacle wearers experience?

A

barrel distortion

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17
Q

What are methods to increase the field of view for an aphakic patient?

A
  1. dec vertex distance

2. inc lens size

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18
Q

What are the lenses designed to create a “bullseye” appearance and reduce cosmetic issues of aphakic lenses?

A

lenticular lenses

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19
Q

What is the work eyes will have to do to see a single image?

A

phoria

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20
Q

For aphakic patients, what is the movement necessary for each degree of pantoscopic tilt?

A

lower frame 0.5mm

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21
Q

For normal patients glasses, what is the movement necessary for each degree of pantoscopic tilt?

A

lower OC 0.5mm

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22
Q

What are methods to increase the field of view for an aphakic patient?

A
  1. dec vertex distance

2. inc lens size

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23
Q

How will unilateral aphakia patients achieve binocular vision with spectacle lenses?

A

not possible

24
Q

What are ways to reduce minification in high myopes?

A
  1. dec vertex distance

2. fit CL

25
Q

Which have larger retinal image sizes: refractive myopes or refractive hyperopes?

A

both the same

26
Q

What lenticular lens is a small concave disk ground on the back surface of plano lenses called?

A

myodisc

27
Q

What are methods to minimize edge reflections?

A
  1. edge coating
  2. edge painting
  3. semitransparent edge
  4. buffing edge
  5. tinting lens
  6. hide-a-bevel
28
Q

What is the retinal image size directly proportional to?

A
  1. angle that the incident chief ray makes with optic axis

2. axial length of eye

29
Q

What is the comparison of the size of the retinal image of the eye, with the correcting lens, to the size of the retinal image of the emmetropic eye?

A

relative spectacle magnification

30
Q

What are each of the following labels for spectacle frame measurements:

  1. A
  2. B
  3. GC
  4. DBC
  5. DBL
  6. ED
A
  1. eye size, horizontal size
  2. vertical size
  3. geometric center
  4. distance between centers, frame PD
  5. distance between lenses, bridge size
  6. effective diameter
31
Q

Which have larger retinal image sizes: corrected axial myopes or corrected axial hyperopes (assuming both at the primary focal plane)?

A

both the same

32
Q

What is the equation for the minimum blank size?

A

MBS = ED+2(decentration)

33
Q

What impacts the spectacle magnification?

A
  1. the power

2. the shape (form) of the lens

34
Q

What is the comparison of the size of the retinal image of the eye, with the correcting lens, to the size of the retinal image of the emmetropic eye?

A

relative spectacle magnification

35
Q

What does the frame PD equal?

A

DBC or A+DBL

36
Q

What is the rule that states the prismatic effect at any point on a spherical lens is equal to the distance off the point from the pole of the lens (in cm) multiplied by the power of the lens?

A

Prentice’s Rule

37
Q

What is the standard rule for obliquely crossed prisms? 1. What must be true for this to work? 2

A
  1. same base: add prisms; opposite base: subtract prisms

2. monocular

38
Q

Where is light deviated towards in regard to the base of the prism?

A

to the base

39
Q

What is one prism diopter equal to in terms of displacement at a certain distance?

A

1 cm at a distance of 1 m

40
Q

Where is an image shifted to in terms of the base of the prism?

A

shifted towards apex

41
Q

When are PRP and OC not the same?

A

prism present

42
Q

What is the location on the lens where the desired prismatic effect should be verified?

A

prism reference point

43
Q

What point on the lens should always be located directly in front of the patients pupils when looking in primary gaze?

A

PRP

44
Q

What is the amount and direction of the displacement of the pole of the lens from the geometric center of the lens box?

A

decentration

45
Q

What kind of prism would be used to fix an eso? 1. An exo? 2. A hyper? 3

A
  1. BO prism
  2. BI prism
  3. BD in front of hyper eye
46
Q

When are PRP and OC not the same?

A

prism present

47
Q

What happens to the prismatic effect as the vertex distance increases? 1. What distance of objects does this apply to? 2

A
  1. decreases

2. near objects

48
Q

What type of lenses require more rotation to see in the periphery?

A

plus lenses

49
Q

How great is the convergence demand for myopes in glasses compared to contacts?

A

decrease demand in glasses

50
Q

What are the two methods to create prism?

A
  1. grinding

2. decentration

51
Q

What are a series of identical small prisms lying adjacent to each other on a thin base called?

A

Fresnel prisms

52
Q

What are the benefits of Fresnel prisms?

A
  1. thin
  2. lightweight
  3. in-office application
  4. easily changable
53
Q

What are the disadvantages of Fresnel prisms?

A
  1. dec VA
  2. dec contrast
  3. striated appearance
54
Q

What are the effects of excessive base down prism?

A
  1. floor and other horizontal expanse to seem concave
  2. people and vertical objects seem taller
  3. patient feels like walking uphill
55
Q

What are the effects of excessive base up prism?

A
  1. floor and other horizontal expanse to seem convex
  2. people and vertical objects seem shorter
  3. patient feels like walking downhill

II. Ophthalmic Optics (3 decks)

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