Brainscape's Knowledge GenomeTM

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


See full index

Ophthalmic Optics Block 10 > Phys And Optical Characteristics Of Lenses 2 > Flashcards

Phys And Optical Characteristics Of Lenses 2 Flashcards

1
Q

Light incidence on a surface suffers a combination of three fates

A

Transmission
Absorption
Reflection

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

Tranmission + absorption + reflection=

A

100%

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

When a light passes through a lanes, it is _____ on both lens surfaces and _____ by the lens material

A

Reflected

Absorbed

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

The anoint of light energy that gets through an optical system

A

Transmittance (T)

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

When light falls upon a lens, it is lost in two ways

A

Reflected

Absorbed

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

Specifies the amount of light reflected from a surface

A

Fresnel law

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

Spectacle lens in air fresnels law

A

R= (n2-1/N2-1)^2

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

Converting transmittance

A

Ts-1-R

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

To find transmittance (not absorbed)

A

T=TsTsTm

Ts is transmittance at each surface
TM amount transmitted, not absorbed by the medium

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

How the amount of light transmitted changes based on a change of thickness of the absorbing material

A

Beer-lambert law

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

The fraction of light transmitted per unit lenejgth of solid tinted material

A

Transmittance factor (q)

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

If given:
Q=0.8/mm
Material thickness=4mm
How much light is transmitted

A

(0.8)^4=0.41=41%

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

The ratio of the density of a substance to the density of a reference substance

A

Specific gravity

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

Higher the specific gravity of a material,

A

The more material is packed into a smaller area

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

Substances with specific gravity >1

A

More dense than water (will sink)

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

Substances with specific gravity <1

A

Less dense than water (will float)

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

A diopter equals

A

D=1/f

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

Light passing through a plus lens

A

Converges

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Light passing through a minus lens

A

Diverges

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

Rays of light entering a prism always do what at base of prism

A

Bends towards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

The image through a prism

A

Shifted towards apex

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

A curved interface between two media

A

Single spherical refracting inferfaces

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

An optical system with two spherical refracting interfaces- the front and back surfaces

A

A spherical lens

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

Total lens power =

A

Front lens surface + back lens surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Interface wraps around the lower n medium

A

Concave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Interface wraps around the higher n medium

A

Convex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Concave interface is always

A

Diverging

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Convey interface is always

A

Converging

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Power of SSRI

A

F=(n2-n1)/r

n2=RI of final media
N1=RI of original media
R=radius of curvature of SSRI
F=power of the ssri

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Total lens power

A

F=F1+F2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Refractive power of a surface

A

P=(N2-n1)/r

N1=refractive index of medium
N2=refractive index of emerging rays
R= distance (m)

Simplified to F= (n-1)/r

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Total power of the lens ignores what

A

Thickness

This is approximate power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Front surface power is

A

+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Back surface power is

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Back vertex power

A

Fv= P1/(1-d/n*P1)+P2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Front vertexpower

A

Fn=F2/(1-t/nF2)+F1

37
Q

Vertex distance and tilt

A

When lens is tilted about the optical center the vertex distance doesn’t change along line of sight

38
Q

Optical axis and tilt

A

The optical axis of the lens no longer passes through the center rotation of the eye
-paraxial theory no longer applies

39
Q

Tow forms of tilt

A

Pantoscopic tilt

Face form

40
Q

Horizaontal tilt

A

Panto

41
Q

Vertical tilt

A

Faceform tilt

42
Q

Tilt on lens and cyl and sphere

A

Sphere power reduced in meridian that is tiled

43
Q

Panto tilt of a minus lens

A

Axis at 180

44
Q

Panto tilt of a plus

A

Axis at 90

45
Q

Faceform tile of plus

A

Axis at 90

46
Q

Faceform tilt of a plus

A

Axis at 180

47
Q

Compensating power for tilt

A

A Rx modified for the as worn position when fitted to the frame or mount
-Rx measured on a lensometer does not equal Rx/ordered RX

48
Q

Single vision compensating for tilt

A

Ensure optical axis of the lens passes through the center of rotation by lowering the optical center

49
Q

Compensating for panto tilt

A

Lower it 2mm per 1 degree of tilt

50
Q

Equation for compensating for lens tilt

A

X=dcorsiny

51
Q

Lens form characterizes

A

The relationship between the front and back surface geometries of a lens

52
Q

Form of a lens

A

Specified by the power of the front surface BC

53
Q

BC can be manipulated for 4 reaseons

A

Thickness and wt
Peripheral lens aberrations
Cosmetic considerations
Image size and magnification

54
Q

Plano-convex and Plano-concave

A

One surface is flat and the others s curved

55
Q

Meniscus

A

Convex front surface and concave back surface

Most common

56
Q

Biconvex and biconcave

A

Both surfaces are either convex or concave

57
Q

Equiconvex and equiconcave

A

Half total power is due to the front surface and half is due to the back surface

58
Q

Plano cylinder

A

One flat surface and one cyl surface

59
Q

Toric

A

One topic surface and spherical surface

60
Q

Standard lens curves used by manufactures

A

Base curve

61
Q

Spherical lens BC

A

From spehre curve

62
Q

Toxic base curves and cross curve

A

Back surface

63
Q

Base curve of minus cyl

A

From sohere curve

64
Q

Spherical equivalent

A

Sum of the spherical component and one half of the cyl component of a lens or surface

65
Q

Curve from which all other curves are measured

A

Base curve theory

66
Q

To find the best curve for plus RX, add the sphere power or the spherical equivalent to +6,

A

Vogels rule

67
Q

To find the best curve for a minus Rx, add half the sphere power or half the spherical equivalent to +6

A

Vogels theory

68
Q

You want the BC of the front surface to be as close to _____ as possible

A

+6

69
Q

The height or depth of a lens surface

A

Sag

70
Q

The sagitta of a curve is the

A

Perpendicular distance from the vertex of the curve to a chord intersecting the curve

71
Q

Sag formula

A

S=H2/2r

72
Q

The distance between the posterior pole of ophthalmic lens and perpendicular plane constraint the posterior edge of lens

A

Vertex depth

73
Q

The distance between the anterior pole of the lens and the plane containgin anterior edge of the lens

A

Lens bulge

74
Q

The height of the lens when laid down on a flat surface

A

Plate height

75
Q

Sag of back surface

A

Vertex depth

76
Q

Sag of front surface

A

Lens bulge

77
Q

Sag of front surface + edge thickness

A

Plate height

78
Q

How to account for different RI in lens clock

A

Pclock= (n2-n1)clock/r
Rearranged to

R=(n2-n1)clock/Pclock

Ultimately
Ptrue=Pclock((n2-n1)true)/(n2-n1)clock

79
Q

When a frame is put on a patients face, it should touch at three points

A

The fitting trial
-ear and skull
Bridge of nose

80
Q

4 pt alignment

A 
Tighten the screw 
X-int 
Co-planar
Skewed bridge 
Faceform 
Panto tilt 
Parallel temples 
Nose pads
Open temple angle 
Clean
81
Q

Check for misalignment when viewing the frame from above

A

Co planar

-occurs when the bridge us pushed forward/backward while the lenses remain in correct tilt

82
Q

Check for misalignment when viewing from above

A

X-int

Lenses twisted where eyewires meet the bridge

83
Q

Check for misalignment when looking straight on

A

Skewed bridge/eyewires

Lenses are rotated inward or outward around the bridge

84
Q

Check curvature of fram from above

A

Faceform

Too much=changes in perceived lens power

85
Q

Check for alignment where viewed from

A

The side

Some panto is necessary for cosmetics and optics

86
Q

Check for misalignment by placing the eyewear temples up on flat surface and checking from the side

A

Parallel temples

Both temples should make contact with flat surface

87
Q

Check from above for 90 angle

A

Open temple angle

Should never be less

88
Q

Check from back when temples are closed

A

Temple fold angle

Temple tips should not touch the lenses, be parallel and cross at middle

89
Q

Check all three of these for alignment, frontal, splay, vertical)

A

Nose pads

Ophthalmic Optics Block 10 (4 decks)

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