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NBEO Part 1 > Optics > Flashcards

Optics Flashcards

1
Q

Convex lens

A

Wraps around material with the higher n value. Positive (i.e. converging)

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2
Q

Concave lens

A

Wraps around material with a lower n value. Negative (i.e. diverging)

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3
Q

When do you get internal reflection

A

When n2

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4
Q

What happens to power of lens as you move them from the eye

A

Become more plus

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5
Q

What happens to the power of lenses as you move them closer to the eye

A

Become more minus

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6
Q

Aperture Stop

A

Limits the amount of light entering the system

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7
Q

Field stop

A

Limits the size of an object that can be imaging

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8
Q

Entrance Pupil

A

Image of the aperture stop formed by lens in front of aperture stop

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9
Q

Exit pupil

A

Image of the aperture stop formed by lenses behind aperture stop.

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10
Q

Depth of focus

A

Area on the retina where an image can be clear

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11
Q

Depth of field

A

Area of an object that can be clear without accommodaiton

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12
Q

What increases DOF

A

Decreased aperture and decreased focal length.

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13
Q

Field of view

A

The extend of an object that can be imaged

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14
Q

Lenses and FOV

A

Minus increase FOV. Plus decrease FOV.

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15
Q

Panto tilt of a minus lens

A

minus cylinder at 180

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16
Q

Face form tilt of a minus lens

A

Minus cylinder at 90

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17
Q

Cl always require more…

A

Plus power

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18
Q

Spectacles always require

A

More minus power

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19
Q

Properties of indirect

A

Larger FOV, less magnification, inverted, larger Depth of focus.

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20
Q

Prism with lensometer

A

Base is wherever the lines are. I.e. line above bullseye means BU

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21
Q

What is the cornea in keratometry

A

A convex mirror (negative). Measure the size of the reflected image.

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22
Q

How do you get BC from radioscope

A

The distance between the two clear images.

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23
Q

What do keratometers assume

A

N=1.3375

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24
Q

Magnification of funds lens

A

M=-Feye/Flens

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25
Q

High mass impact ANSI

A

Pointed projectile, 500 g from 50 inches.

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26
Q

High velocity impact

A

Steel ball, 0.25 inches in diameter, fired at 150 feet per second.

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27
Q

Spherical lenses base curve

A

Front sphere curve

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28
Q

Minus cylinder lens base curve

A

Front sphere curve. Back flatter curve is topic base curve. other back curve is cross curve

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29
Q

Base curves for contact lens

A

typically on back surface

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30
Q

What to do if seg is too low

A

decrease panto tilt, shrink the bridge, increase vertex distance, move pads down, narrow the pads.

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31
Q

Spherical abberation

A

Marginal rays bend more than axial rays. Don’t have to consider too much as pupil blocks out. On and off axis.

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32
Q

Coma

A

On axis only. Magnification is varied by height of incident rays above the axis is varied. Results in a comet shaped patch.

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33
Q

When do we need to worry about spherical aberations

A

Very high powered lenses. use aspheric lenses.

34
Q

Radial Astigmatism

A

Due to rays hitting the lens surface obliquely. A flat object plane gives a warped image plane.

35
Q

Tschnering Ellicple

A

How to get rid of radial astimagism. Wollaston is bigger bc so typically use Ostwalt.

36
Q

Curvature of Field

A

Warpage of the plane. Due a plane image be formed as a curve.

37
Q

Point Focal Lens

A

A lens corrected completely for radial astigmatism.

38
Q

Perceived form lens

A

A lens corrected completely for curvature of field.

39
Q

Pincushion

A

Plus lens

40
Q

Barrel

A

Minus lens

41
Q

How does power affect CA

A

Greater power mean more CA.

42
Q

Slab off

A

Correct vertical imbalance. Slab off on the more minus lens (BUMM). Makes the lower half have more BU.

43
Q

Fo every 1D difference in power there will be ____ percent difference in size

A

1

44
Q

How much aniseikonic can a person handel

A

3%

45
Q

How much residual astigmatism can a patient handel

A

1.00 D WTR 0.75 D ATR

46
Q

Ideal edge thickness

A

Thickness of -3 for promoting lid attachment

47
Q

How to change edge lift

A

Change the peripheral cruve

48
Q

Excessive edge lift

A

Movement, awareness of edge. 3 and 9 staining

49
Q

Inadequate edge lift

A

No movement, no complains, no tear exchange

50
Q

Pros/cons of center thickness thin

A

Increased O2 transport, more comfort, more contraption. Con: flexure

51
Q

The more _____ the center of gravity the better the centration

A

Posterior

52
Q

Spherical fit over WTR

A

Fluorescent will pool in vertical meridian and touch in horizontal.

53
Q

Spherical fit over ATR

A

Flurzscene will pool in horizontal and touch in vertical.

54
Q

Bitoric Ridge Lens

A

Use when corneal astigmatism is <2.50. Need back to fit and then front to compensate for greater induced astigmatism.

55
Q

How are most bitorics fit

A

0.25D flatter than K

56
Q

The 2 biotic fitting guides

A
  1. Saddle fit: Both principle meridians fit by 0.25D flatter 2. Low topic stimulation: On K to 0.25D flatter in the flat corneal meridian and 0.75D-1D flatter than K for the steep meridian. Creates 0.75D WTR for a better fit.
57
Q

Back Toric CL

A

Can only use if corneal astigmatism >2.5 and lenticular astigmatism is 1.5Xcorneal

58
Q

Front surface CL

A

Use if corneal astigmatism <2.50 but great lenticular.

59
Q

What do you often have to do with front surface CL

A

Use periballisting to stop rotation (BD prism in the bottom)

60
Q

When do you use front surface aspheric CL

A

When lots of residual or hyperacidity demands

61
Q

When do you use back surface CL

A

Use with ATR astigmatism, irregular astigmatism, or borderline corneal astigmatism

62
Q

Flexure vs. warpage

A

Flexure on eye. Warpage anytime.

63
Q

When do you get more flexure

A

Thinner lenses, more astimagism, thicker, high dk, increase in OZD

64
Q

Silicone Acrylate vs. floor-silicone acrylate

A

Fluor is the boss. Silicon has flexure, warpage, and deposits.

65
Q

Hype ropes Dk material

A

High Dk for daily and hyper high for extended. (thicker center)

66
Q

Myopes DK material

A

low dk for daily and high for extended

67
Q

When can you fit a patient in a spherical CL

A

<100 WTR or <0.75 ATR

68
Q

Prism balasting

A

BD prism in the bottom of the lens.

69
Q

Peribalasting

A

BD prism but only outside of OZ

70
Q

Dynamic stabilization

A

Both the superior and inferior are thinned.

71
Q

Eccentric lenticulation

A

Inferior and superior front portions of the contact lens outside the OS are removed. Periballasting and dynamic.

72
Q

Truncation

A

Lower low contact lens is removed

73
Q

Rotation left

A

clockwise

74
Q

Rotation RIght

A

Counterclockwise

75
Q

How are soft contact lenses typically fit with bc

A

4 D flatter than K

76
Q

Diameter with soft contact lenses

A

HVID + 3 mm

77
Q

High water content in traditntal hydrogel

A

More permeability

78
Q

High water content in silicon hydrogel

A

less silicon so less oxygen permability

79
Q

Peli robison

A

Letters the same size with decreasing contrast

80
Q

Balie Lovie

A

Same contrast with letter increasing or decreasing in size.

81
Q

Do neutral density filters affect contrast?

A

NO. all wavelengths are still transmitted equally. Just less of them.

82
Q

Blue blockers

A

have increased contrast and less glare.

NBEO Part 1 (17 decks)

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