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BRUTE FORCE OPHTH PREP PART 1 > OPTICS MADE EASY > Flashcards

OPTICS MADE EASY Flashcards

1
Q

Methods To Assess Visual Acuity In Children:
Preverbal

A

Little Children like playing with CAR & CAT
* STYCAR
* CATFORD DRUM
* VEP

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2
Q

Methods To Assess Visual Acuity In Children:
18-24 months

A

Toddlers like playing in the GARDEN with CARS, PICTURES and
CARDS
* Sheridan Gardiner Test
* Kay’s Picture
* StyCAR
* CARDIFF CARDS

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3
Q

Visual Acuity Testing In Adults:

A
  • Snellen VA test (most widely used)
  • Logarithum of minimal angle of resolution (LOGMAR)
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4
Q

Contrast Is Measured With: (2)

A
  • PeliRobson Chart
  • Visitech
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5
Q

Stereopsis Is Measured With: (4)

A

Feel, Think Twice & Live
* Frisby
* Titmus
* TNO
* Lang stereotest

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6
Q

Color Vision Is Tested With: (4)

A
  • Lanthony New Color Test (can be used for children)
  • Ishihara
  • FM hue 100
  • D-15
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7
Q

Color Vision Defect: Deuteranopia

A

Dear Girls, Please Remember To Bake
Green cones deficiency

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8
Q

Color Vision Defect: Protanopia

A

Dear Girls, Please Remember To Bake
Red cones deficiency

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9
Q

Color Vision Defect: Tritanopia

A

Dear Girls, Please Remember To Bake
Blue cones deficiency

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10
Q

Refraction image formed at plane surface:

A

LIVE
* Laterally Inverted
* Virtual
* Erect

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11
Q

Prism image formed at plane surface:

A

Image formed by the prism: EVA
. Erect
. Virtual
. Displaced towards the Apex

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12
Q

One Prism Dioptre

A

One prism dioptre produces a linear displacement of 1
cm of an object at 1 m

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13
Q

Increased Prismatic Power In Periphery Of Lens Can Cause

A

SJS
* Spherical aberration
* Jack-in-the-box phenomena
* Scotoma -Ring scotoma

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14
Q

What is Maddox Rod used for

A

Maddox Rod is used to detect ocular Muscle imbalance

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15
Q

Prismatic Effect Of Lens: Formula

A

P= F x D
* P is prismatic power, F is dioptric power and D is distance in centimeters

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16
Q

Does Colour Blindness affect duochrome test?

A

Color blindness doesn’t invalidate duochrome test as it
depends on the position of the image with respect to retina

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17
Q

SRK formula

A

P=A-B(AL)-C(K)
P= IOL POWER
A constant of model lens
B 2.5 constant
C 0.9
AL axial lenght
K K reading

2509

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18
Q

loupe/ simple magnifying glass formula

A

M = F/4

M= Magnifying power
F =lens power in diopter

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19
Q

Accommodative power formula

A

A= V-R
A= accommodative power
unfinished

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20
Q

Spherical equivalent formula

A

SE= sphere + cyl/2 (100 plus)

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21
Q

Angle of deviation of prism

A

Rough Rheumatoid Arthritis
* Refractive index of prism
* Refracting angle of prism
* Angle of incidence of ray

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22
Q

Power in Prentice position

A

One prism surface is perpendicular to the ray of light

Normally specified for glass prisms i.e trial lens prism

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23
Q

Diagnostic uses: PRiSMS

A
  • 4D Prism test for microtropia
  • Reserve (fusional] to assess BSV
  • Squint angle measurement
  • Maddox rod
  • Simulated blindness assessment
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24
Q

The advantage of CL

A

increased field of view and decreased optical aberrations

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25
Q

Disadvantage of CL

A

demands greater convergence and accommodation in Myopes

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26
Q

How many prism D can be put in CL

A

Upto 3 D prism can be put in CL

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27
Q

Wavelengths absorbed by cornea and sclera

A

The cornea and sclera absorb all the very short wavelengths
in UV-B & UV-C and very long wavelengths in IR-B & IR- C radiations

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28
Q

Wavelengths absorbed by human lens

A

The human lens absorbs UV-A light while IR-A radiation
passes through the ocular media along with the visible light

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29
Q

The degree of chromatic aberration in the human eye

A

2-3 dioptres

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30
Q

Geneva lens measure assesses

A

The Geneva lens measure assesses the surface curvature of a lens

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31
Q

Prentice position of a prism occurs

A

when one surface of the prism is normal to the ray of light so that all deviation occurs at the other surface

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32
Q

Maddox Rod: subjective check deviation

A

Horizontally to check for Horizontal muscle imbalance and
vertically for Vertical one

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33
Q

Example of refractive index: Air

A

1

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34
Q

Example of refractive index: Aqueous humour

A

1.33

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35
Q

Example of refractive index: crown glass

A

1.52

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36
Q

Example of refractive index: Diamond

A

2.5

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37
Q

Total Internal Reflection

A

Rays entering more oblique than critical angle don’t emerge from denser medium and reflected back

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38
Q

Total Internal Reflection examples

A

Fibre optic cables, Cornea air interface in eye

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39
Q

Total Internal Reflection in eye can be overcome by:

A

Can be overcome with contact lens with a higher refractive index than eye

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40
Q

Wavelength

A

wavelenght of a wave is the distance between two successive peaks of propagation.

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41
Q

One oscillation is

A

defined as the segment of the wave where it returns to the start, which is also known as one cycle

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42
Q

Amplitude

A

is a maximum displacement of the wave from its baseline.

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43
Q

Interference

A

Interference is the phenomenon where two or more waves interact with one another.

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44
Q

Diffraction

A

Diffraction is described as the apparent bending of a wave around an obstacle.

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45
Q

Airy disc

A

Diffraction through a circular aperture causes a diffraction pattern where there is a central bright disc

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46
Q

Airy pattern

A

Airy disc that is surrounded by alternating light and dark rings, together known as the Airy pattern.

47
Q

How does the size of the aperture affects the size of the Airy disc:

A

The smaller the aperture the larger the disc. This is because diffraction is most prominent in smaller apertures.

48
Q

Radiant flux measured in?

A

(measured in watts) is the radiometric equivalent of luminous flux (measured in lumens)

49
Q

A luminous flux measured in?

A

lumen

50
Q

Luminous flux

A

Luminous flux is photometric, and quantifies how much light is emitted from a point source.

51
Q

Radiant intensity

A

Radiant intensity (the equivalent of luminous intensity) considers the intensity of light in a given solid angle.

52
Q

Irradiance

A

Irradiance (the equivalent of illuminance) is the amount of light falling on a given surface area.

53
Q

Jackson cross cylinder

A

Sphero-cylindrical lens wherein the
power of the cylinder is twice the power of the sphere and of the
same sign.

54
Q

Coma

A

Spherical aberration

Coma results from spherical aberration which causes light rays from a point source (spherical source) to be distributed in the shape of a comet.

55
Q

4 PD base out prism test is most useful for diagnosing

A

central suppression scotoma

56
Q

direct ophthalmoscope image is

A

virtual and erect

57
Q

direct ophthalmoscope magnification

A

15x

58
Q

direct ophthalmoscope field

A

2DD

59
Q

Indirect ophthalmoscope magnification

A

3x or 5x

60
Q

Indirect ophthalmoscope field

A

8DD

61
Q

Indirect ophthalmoscope image is

A

Real and inverted

62
Q

Optical radiation lies between

A

X-rays and microwaves in the electromagnetic spectrum

63
Q

400 – 780

A

Visible radiation

64
Q

315 – 400

A

UVA light

65
Q

280 – 315

A

UVB light

66
Q

200 – 280

A

UVC light

67
Q

780 – 1400

A

IRA light

68
Q

1400 – 3000

A

IRB light

69
Q

3000 – 10000

A

IRC light

70
Q

Laws Of Reflection (2)

A

1) Incident Ray, Reflected Ray & Normal all lie on same plane
2) Angle of incidence is equal to angle of reflection

71
Q

Absolute Refractive Index

A

Velocity of light in VACUMN/velocity of light in that medium

72
Q

Refractive Index

A

Velocity of light in AIR/velocity of light in that medium

73
Q

Example of refractive index: Flint glass

A

1.6

74
Q

Total Internal Reflection:

A

Rays entering more oblique than critical angle don’t emerge from denser
medium and reflected back, known as Total Internal Reflection

75
Q

Examples of Total Internal Reflection

A

Fibre optic cables, Cornea air interface in eye

Can be overcome with contact lens with a higher refractive index than eye

76
Q

priSm obeys Snell’s Law

A

YES

RAY passing through prism deviates towards Base of prism

IMAGE is displaced towards Apex of prism

77
Q

Position of minimum deviation

A

Angle of incidence is equal to angle of emergence

Specified for plastic ophthalmic prisms i.e prism bars

78
Q

POWER in Prentice position

A

Power in Prentice position is greater than in position of minimum deviation

79
Q

Therapeutic uses: CD

A
  • Convergence insufficiency
  • Diplopia i.e small vertical/paralytic squints, decompensated
    heretrophorias
80
Q

Ophthalmic instruments in which prisms are used:

A
  • Slit lamp
  • Applanation Tonometer
  • Keratometer
81
Q
A

Porro Prism

*Can deviate incident ray by 180
*Causes total internal reflection
*Image is inverted but not transposed left to right

82
Q
A

Dove Prism

*Rotates image by 180 degree
*Image is inverted but not laterally transposed

83
Q
A

Right Angle Prism

*Deviates the incident ray by 90 degree
*Also known as reflecting prism
*Produces inverted image

84
Q
A

Risley Prism:

*Two prisms in front of each other that can rotate with respect to
each other
*Measures phoRias!

85
Q

One prism dioptre produces

A

a linear displacement of 1 cm of an object at 1 m

86
Q

1 PD=

A

1 PD=1/2 degree

87
Q

converging lens

A

Biconvex

88
Q

diverging lens

A

Biconcave

89
Q

Lens

A

Portion of refracting medium bordered by two curved surfaces which have common axis

90
Q

Convex/Converging Lens: uses

A

Is used to correct hypermetropia, presbyopia & aphakia

  • Can be used as low vision aid
91
Q

Concave/Diverging: uses

A

Is used to correct myopia

92
Q

Dioptric Power Of Lens:

A

F=1/f2 (F is Dioptric power and f2 is focal length in meters)

*Lenses of shorter focal length are more powerful

93
Q

Prismatic power increases

A

Prismatic power increases in the Periphery of spherical lens

94
Q

Use of non-axial portion of lens to gain a psimatic effect is called

A

Use of non-axial portion of lens to gain a psimatic effect is called decentration of lens

95
Q

Maddox Rod: type of lens

A

convex-cylindrical lens

96
Q

Maddox Rod : rod is place at which eye?

A

right eye

97
Q
A

Esophoria (uncrossed)

98
Q
A

Exophoria

99
Q
A

Hypophoria

100
Q
A

Hyperphoria

101
Q
A

Vertical orthophoria

102
Q

Toric Surface

A

When cylindrical lens is bent, XY becomes an arc, that’s known as Toric
surface

103
Q

Principal meridians toric

A

The meridians of maximum and minimum curvature are called principal
meridians

104
Q

base curve toric

A

The principal meridian of minimum curvature is called base curve

105
Q

Jackson Cross Cylinder

A

It is a sphero-Cylinder in which the power of Cylinder is double than that of
sphere and of opposite sign

  • Is used to check the axis and power of cylinder
106
Q

Jackson Cross Cylinder: check axis

A

To check the Axis: the handle is held in line with the axis of trial cylinder
(HAA)

107
Q

Jackson Cross Cylinder: check power

A

To check the power: The axis is held in line with the axis of trial cylinder
(AA)

108
Q

Focimeter:

A
  • Measures power and axis of a lens
  • Green light is used
  • FoCusIng system has Collimating lens (to make light parallel) and Illuminated
    target
109
Q

Prismatic Effect Of Lens: formula

A

P= F x D

P is prismatic power, F is dioptric power and D is distance in centimeters

110
Q

Photochromic lens changes its color according to

A

Intensity of incident radiation

Photochromic lens changes its color according to intensity
of incident radiation

111
Q

Thickness of Antireflective coating

A

Thickness of Antireflective coating is 1/4th of incident light, that causes destructive interference

112
Q

Chromatic Aberration:

A

dispersion of white light into its constituent colors is called chromatic aberration

  • Decreased wavelength causes more deviation
  • It’s Independent of refractive index
113
Q

Chromatic Aberration can be overcome by

A

achromatic lens system

(achromatic lens system in which concave lens of high
dispersive and low reflective power is combined with convex lens of high
reflective but low dispersive power)

114
Q
A

BRUTE FORCE OPHTH PREP PART 1 (10 decks)

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