Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Ophthalmic Optics > 6 - Corrective Curve Lens Design - Exam 2 > Flashcards

6 - Corrective Curve Lens Design - Exam 2 Flashcards

1
Q

What dioptric power does the back surface of a periscopic lens have?

A

-1.25 D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What dioptric power does the front surface of a meniscus lens have?

A

+6.00 D

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which aberration were the first corrective curve lenses designed to minimize?

A

Radial astigmatism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is true about base curves that correct or minimize one type of aberration?

A

They often make another type of aberration worse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Would a patient with high sensitivity to chromatic aberrations be more receptive to a high or low abbe value material?

A

High abbe value

Chromatic aberrations minimized

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 5 types of Seidel (third-order) aberrations?

A
  1. Spherical aberration
  2. Coma
  3. Radial astigmatism (AKA oblique astigmatism)
  4. Curvature of field
  5. Distortion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which 2 types of third-order aberrations are minimized by the pupil?

A
  1. Spherical aberrations

2. Coma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which 2 types of third-order aberrations are minimized by selecting the appropriate base curve?

A
  1. Radial astigmatism

2. Curvature of field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Which type of third-order aberration can not be eliminated, but also is the least problematic?

A

Distortion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the 2 most important types of off-axis aberrations to control?

A
  1. Radial astigmatism

2. Curvature of field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where is a hyperope’s far point located?

A

Behind the eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the far point sphere?

A

The locus of far points for all possible viewing angles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

For radial astigmatism, will the tangential focus or the sagittal focus be closer to the lens?

A

Tangential focus

Effective tangential power > Effective sagittal power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How many mm should you drop the optical center for 2 degrees of pantoscopic tilt?

A

1 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

If you drop the optical center 1 mm, how many degrees of pantoscopic tilt are you accounting for?

A

2 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In what type of eyewear are the effects of radial astigmatism and induced prism especially apparent?

A

Wrap-around prescription eyewear

17
Q

What are 2 other names for curvature of field error?

A
  1. Petzval surface

2. Power error

18
Q

How does the curvature of the Petzval surface compare to the curvature of the far point sphere

A

Petzval surface is usually flatter

19
Q

What type of lens corrects radial astigmatism completely but leaves the curvature of field uncorrected?

A

Point focal lens

20
Q

What type of lens minimizes the power error but leaves residual radial astigmatism?

A

Percival form lens

21
Q

What type of lens partially corrects both curvature of field error and radial astigmatism?

A

Minimum tangential error form lens

22
Q

Which type of corrective curve (or best form) lens is most common?

A

Minimum tangential error form lens

23
Q

What are 4 important parameters to consider with lens design?

A
  1. Vertex distance
  2. Lens thickness
  3. Refractive index
  4. Front and back lens surface powers
24
Q

What is the purpose of a Tscherning ellipse?

A

Tell what base curves eliminate radial astigmatism for a given lens power

25
Q

Where does the Tscherning ellipse not cover, and what does this mean?

A

Does not extend into high plus power range

Radial astigmatism can not be eliminated for aphakes or high hyperopes

26
Q

How is Tscherning’s ellipse used in the real world?

A

Divided into sets of prescriptions for a given base curve (+10 BC for high plus, +2 BC for high minus, etc.)

27
Q

What base curve does a plano lens usually have?

A

+6.00 D

28
Q

How does the back surface of a lens change as you increase minus power?

A

Back surface gets steeper with more minus

29
Q

How does the back surface of a lens change as you increase plus power?

A

Back surface gets flatter with more plus

30
Q

What is Vogel’s formula for a plus lens?

A

BC = Spherical Equivalent + 6.00 D

31
Q

What is Vogel’s formula for a minus lens?

A

BC = Half of the spherical Equivalent + 6.00 D

32
Q

For different powered left and right lenses, which base curve should you choose if both lenses are plus?

A

The steeper base curve

33
Q

For different powered left and right lenses, which base curve should you choose if both lenses are minus?

A

The flatter base curve

34
Q

For different powered left and right lenses, which base curve should you choose if one lens is plus and the other is minus?

A

The base curve with the higher numerical value (steeper)

35
Q

What base curve are most frames designed to be used with?

A

+6.00 D

36
Q

How may plus lenses need to be altered to fit in metal frames?

A

They may need to be flattened

37
Q

How may minus lenses need to be altered to fit in metal frames?

A

They may need to be steepened

38
Q

What is the effect of prism on magnification of a lens?

A

Increases magnification

Due to an increase in lens thickness

39
Q

What may be used to reduce prismatic effects?

A

A flatter base curve

Ophthalmic Optics (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions