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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?

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

58
Q

direct ophthalmoscope field

59
Q

Indirect ophthalmoscope magnification

60
Q

Indirect ophthalmoscope field

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

65
Q

280 – 315

66
Q

200 – 280

67
Q

780 – 1400

68
Q

1400 – 3000

69
Q

3000 – 10000

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

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

88
Q

diverging lens

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?

97
Q
A

Esophoria (uncrossed)

98
Q
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)

BRUTE FORCE OPHTH PREP PART 1 (10 decks)

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