Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Ophthalmic Optics Block 10 > Physical And Optical Chara Of Ophth Lenses > Flashcards

Physical And Optical Chara Of Ophth Lenses Flashcards

1
Q

Relating to the eye, this refers to the interval surrounding the retina in which an eye sees an object in focus

A

Depth of focus

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

Short focal length leads to _______ depth of field

A

Large

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

The interval surrounding the fixation plane in which an object can reside and still be in focus

A

Depth of field

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

An increase in aperture size and depth of field

A

Decreases depth of field and depth of focus

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

Create optical distortions in image quality or a deformation of the image plane

A

Aberrations

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

Two types of aberrations

A

Monochromatic and chromatic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Wavelength independent aberrations

A

Monochromatic aberrations

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

Monochromatic aberrations that distort image quality

A

Spherical
Coma
Radical astigmatism

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

Monochromatic aberrations that deform the image plane

A

Curvature of field

Distortion

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

Chromatic aberrations

A

Longitudinal

Transverse

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

An aberration that occurs when peripheral rays focus at different points on the optic axis than the parasail rays

A

Spherical aberrations

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

Length of a blur circle

A

Longitudinal SA

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

Area size of blue circle

A

Lateral SA

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

What is the basis for SA

A

Paraxial approximation is not always valid

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

Increase in pupil size leads to a _____ in quality of image due to _______ aberrations

A

Decrease

Increased

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

Point of focus of a beam of light is dependent on where the light stroked the optical system

A

Longitudinal SA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Marginal rays focus to a different location compared to parazial rays

A

Longitudinal SA

-a point object is no longer forming a point image (the image is blurred)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Results from the fact that mag is varied as the height of incident rays above the axis varied

A

Coma

  • asymmetric comet-shape patch
  • only in off-axis point sources
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Relevance of SA and coma

A

Largely irrelevant to ophthalmic optics because the small pupil size only accepts paraxial rays
-very high powered lenses-necessary to compensate for spherical aberration by using aspheric lenses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Two factors that influence the effective power of a lens

A
  • Increase in vertex distance for peripheral viewing resulting in a positive shift in effective power for plus and minus lenses
  • light rays strike at an oblique angle inducing astigmatic and spherical error
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Spherical error

A

Field curvature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Cylinder error

A

Oblique astigmatism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Other terms as oblique astigmatism

A

Radical astigmatism or marginal astigmatism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Due to rays hitting the lens obliquely causing the power to be altered by this tilt of the lens

A

oblique astigmatism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is the most important aberrations in lens design
OA
26
A flat object plane yields an asymmetrical warped image plane
OA
27
As the eye rotates towards the periphery, the tangential and Sagittarius planes move furthers from the far point sphere
OA | Teacup and saucer
28
The power along the tangential meridian in the periphery of a lens, the difference between this and Sagittal powers is the oblique astigmatism
Tangential power
29
The power along the sagittal meridian in the peripheral of a lens. The difference between this and tangential powers the OA
Sagittal power
30
Power error
Curvature of field
31
If for each point on that paper,we find the image point we will notice that the image points formed by all points on the paper do not lie on a plane. This means that image plane is warped, even for a lens that is not tilted. This would mean that the quality of an image on a flat screen decreases for larger distances
Curvature of field (power of error_
32
Related to OA when there is a different warping along two principal axis
Curvature of field | -stil have warping without OA
33
Image surface created by a system with no OA, still warped due to curvature of field
Petzval surface
34
Present in ophthalmic optics lens system whenever the petzval surface does not correspond to the far point sphere of the eye
Curvature of field
35
Lenses that have been corrected for OA, curvature of field, or both are corrected curve lenses
Corrected curve theory
36
A lens corrected completely for radial astigmatism, but curvature of field is incorrect yes
Point focal lens
37
A lens corrected completely for curvature of field, OA uncorrected
Percival form lens
38
Results from magnification of a point object depends on the objects distance from the optical axis. Straight line objects form straight line images only if the line passes through the optic axis, all other lines will be curved
Distortion
39
How can distortion be minimized
Correctly placing stops
40
What are the two types of distortion
Barrel and pincushion
41
When is distortion a problem
For high powered lenses
42
Which aberration is of the most concern to lens designers
OA
43
Teacup and saucer image
OA
44
How can OA be reduced
Picking the correct base curves
45
Shows best base curve for eliminated OA
Tscherning ellipse
46
If incorrect BC used in OA
Vision reduced in periphery
47
Limitation of Tschrening ellipse
Upper limit is +7.50 Lower limit is -22.00D Outside the limits-aspheric lenses
48
An optical system (a lens) will alter the properties of light striking it in a predictable way
Vergence
49
Measures the degree of converging or diverging of a light wave at a given point in space
Vergence
50
Negative vergence
Diverging light
51
Positive vergence
Converging light
52
Image vergence equation
Object vergence + power | V=U+P
53
Exiting light with a positive vergence
Real images
54
Exiting light with a negative vergence
Virtual image
55
Incident light with a negative vergence
Real object
56
Incident light with a positive vergence
Virtual object
57
Incident rays are close to the optical axis, which yields point images for point objects
Paraxial approximation
58
The line joining the centers of curvatures of the two surfaces of a lens and passes through the lens at the optical center
Optical axis
59
Optical axis is _________ to each surface, so light passing though the axis is undeviated
Perpendicular
60
The axis perpendicular to the muscles plane around which the eye rotartes when acted on
Axis of rotation
61
Change in vergence of light that occurs at different points along its path (related to vertex distance) -two lenses have the same effective power if they form a real or virtual image of an object at the same point
Lens effectively
62
Rays on the periphery, far from the optical axis
Marginal rays
63
Rays in close proximity to the optical axis
Parazial rays
64
Limits an optical systems field of view s
Stops
65
Physical entity limits the amount of light passing into an optical system when viewing an object, could be an actual aperture, like in a camera, or another physical element, light the edge of a lens
Aperture stop
66
This limits the size of the object that can be images by the system
Field stop
67
Light waves travel through transparent media at different speeds
Refraction index
68
The ratio of the spend of light in a vacuum (or air) to the speed of light in another medium
Refraction index
69
Describes how much a given material will slow down and change the direction of a ray that passes through it
Refraction index
70
The higher the index, the ____a lens can be and produce the same power
Thinner -a -8.00 with an index of refraction of 1.74 will always be thinner than a lens with an index of refraction of 1.586 with the same power
71
Dependent on the wavelength leading to chromatic dispersion
Refraction
72
An on-axis aberration that occurs when different wavelengths of light are focused at different distances from the lens
Longitudinal chromatic aberration (LCA) - dioptric difference between red and blue powers - vary by location - refers to a lens as a whole
73
An off-axis aberration that occurs when different wavelengths of light are focuses at different points in the same focal plane
Transverse chromatic aberrations (TCA) - blue light is deviated more than red light - vary by size - prism diopter
74
Leaders the apprentice of color fringes
Chromatic aberrations
75
Underlies the use of the red green spherical test in clinical refraction
Chromatic aberration
76
Red and green in refraction
Discrepancies between red and green yield a more precise estimate of the refractive error of the ey than would a monochromatic stimulus
77
Quantifies the amount of chromatic aberration of a lens material
Chromatic dispersion
78
The lower the chromatic dispersion, the ______chromatic aberration present in the lens
Less
79
Is lower or higher chromatic dispersion better
Lower
80
Transverse chromatic aberration is more _____to vision
Harmful - results in different prismatic effects for different wavelengths - impacts peripheral viewing
81
How to minimize CA when using materials with low Abbe number
Use shorter vertex distances Monocular PD Add sufficient panto
82
Quantifies the amount of chromatic aberration of a lens material
Abbe number
83
Higher the abbe number, the ____chromatic aberration present in the lenses
Less
84
Is bigger or smaller abbe number better
Bigger
85
Reciprocal of the chromatic dispersive power
Abbe number
86
High index materials, have a ______ abbe number
Lower | -only use this is you value thin lenses over quality of image
87
LCA equation
LCA=F/v V=abbe value F=lens power
88
TCA equation
TCA=dF/v V=abbe value D=distance from optical center of the lens (cm) F=lens power
89
What is a good abbe number
40s into low 50s

Ophthalmic Optics Block 10 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions