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Written Optical Exam > Optical Knowledge > Flashcards

Optical Knowledge Flashcards

1
Q

What is focal length?

A

The distance from a lens where rays of light are said to converge.

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2
Q

Where is the focal length on a minus lens?

A

Behind or to the left of the lens.

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3
Q

Where is the focal length on a plus lens?

A

In front or to the right of the lens.

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4
Q

Are objects minimized or magnified by minus lenses?

A

They are minimized. The objects in the distance go with the movement of the lens.

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5
Q

Are lenses magnified or minimized by a plus lens?

A

They are magnified.

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6
Q

What is the constant for focal length or lens power?

A

1 meter or equivalent

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7
Q

What are the equivalents of 1 meter?

A

1000 mm, 100 cm, or 40 inches

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8
Q

How do you use focal length to get Diopter Power?

A

Divide focal length into the constant to get Diopter Power

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9
Q

How do you get focal lentgth when given diopter power?

A

Divide diopter power into the constant to get Focal Length

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10
Q

What is the resolving power of an emmetropic eye?

A

Resolving power of 1

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11
Q

What does emmetropia mean?

A

Equal

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12
Q

What does ammetropia mean?

A

Needs correction

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13
Q

What is the 5 minute angle?

A

It is independent of distance of the object from the eye.

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14
Q

What is exopthalmos?

A

Pushing forward of the eye/Graves condition

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15
Q

What is the 5 minute angle of an emmetropoic eye?

A

5 minute angle at 20’

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16
Q

What is the resolving power of a 20/40 eye?

A

Reolving powrer of .5

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17
Q

How much larger do letters have to be for a 20/40 eye to reolve at 20’?

A

Letters have to be 2X as large

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18
Q

When is there a 10 minute angle?

A

For a 20/40 eye

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19
Q

How do you figure resolving power?

A 
Take VA (20/60) and divide
Resolving power for 20/60 is .3333
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20
Q

How do you determine the angle?

A

Take VA: 20/60 How many more times is 60 than 20? 3 So 5 times 3 = 15 minute angle

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21
Q

What part of the prism gives you the image?

A

the apex

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22
Q

Where are the rays directed in a prism?

A

To the base

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23
Q

What does a prism do?

A

Bends light, changes the postition of an object, corrects muscle imbalances

24
Q

What is Prenctice’s Rule?

A

P x d (in cm) = Prism amount
P= Lens power in diopters
d= Decentration in .cm

25
Q

What is a tropia?

A

an obvious deviation (no depth perception)

26
Q

What is a phoria?

A

Sometimes there’s a deviation

27
Q

What is an orthoptist?

A

a person who studies eye muscles

28
Q

What is an ocularist?

A

someone who makes artificial eyes

29
Q

Where is the apex of a prism placed?

A

Over the weak muscle

30
Q

Where is the base of a prism placed?

A

Opposite the deviating muscle

31
Q

What is the vertical tolerance for prism?

A

1/3 or .333

32
Q

How do you determine how much the lens is decentered?

A

Amount of prism / Diopter Power= d (in cm)

33
Q

Where is the optical center located in a flat top bifocal?

A

5 mm below top

34
Q

Where is the optical center located in a round bifocal?

A

In the center

35
Q

Where is the optical center located in an executive bifocal?

A

At the top

36
Q

How do you determine the index of refraction?

A

Speed of light in air/speed of light in optical medium=index of refraction of the lens

37
Q

What is the speed of light in air?

A

186,000 miles per second

38
Q

Regarding the power cross, how do you determine the sphere in + cylinder?

A

the sphere is always the lowest + or the most -

39
Q

How do you determine the sphere for minus cylinder?

A

the sphere is lowest - or most +

40
Q

Is high Abbe Value a good thing?

A

Yes

41
Q 
List the following Abbe values:
Glass
CR 39
Hi Index 1.67
Hi Index 1.74
Polycarbonate
A 
70
40
36
34
30
42
Q

Where do light rays focus on an emmetrope?

A

they come to a single point focus on the retina

43
Q

What is accomadative hyperopia?

A

person has enough accommation to overcome their refractive error

44
Q

What is manifest hyperopia?

A

part of the R.E. is taken care of by accommadation, but part is taken care of by lens

45
Q

What absolute hyperopia?

A

all of the R.E. is taken care of by the lens

46
Q

Name the 5 types of astigmatism.

A

Simple myopic, simple hyperopic, compound myopic, compound hyperopic, and mixed

47
Q

What is an isometropia?

A

a person with an equal Rx

48
Q

What is anisometropia?

A

Unequal amoundt: OD: -3.00, OS: -8.00

49
Q

Where is traditional slab-off placed?

A

ON the front surface of the lens

50
Q

Where is reverse slab placed?

A

Back surface of the lens

51
Q

Why is slab-off used?

A

Done for vertical imbalance; traditional slab done on highest minus

52
Q

What is diopter power of the emmetropic eye?

A

Eye=60 D (Cornea=43 D and lens=16-20 D)

53
Q

What are the indices of refraction for the following?

CR 39, Crown Glass, Tools, Cornea, Crystalline Lens, Polycarbonate

A

1.49, 1.523, 1.53, 1.37, 1.42, 1.61

54
Q

What three materials all have the same index of refraction? What is it?

A

Aqueous, Vitreous, Water = 1.33

55
Q

What is the index of refraction of air?

A

1.00

56
Q

What is Jaeger print used for?

A

Near vision

Written Optical Exam (2 decks)

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