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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
Disadvantage of CL
demands greater convergence and accommodation in Myopes
26
How many prism D can be put in CL
Upto 3 D prism can be put in CL
27
Wavelengths absorbed by cornea and sclera
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
28
Wavelengths absorbed by human lens
The human lens absorbs UV-A light while IR-A radiation passes through the ocular media along with the visible light
29
The degree of chromatic aberration in the human eye
2-3 dioptres
30
Geneva lens measure assesses
The Geneva lens measure assesses the surface curvature of a lens
31
Prentice position of a prism occurs
when one surface of the prism is normal to the ray of light so that all deviation occurs at the other surface
32
Maddox Rod: subjective check deviation
Horizontally to check for Horizontal muscle imbalance and vertically for Vertical one
33
Example of refractive index: Air
1
34
Example of refractive index: Aqueous humour
1.33
35
Example of refractive index: crown glass
1.52
36
Example of refractive index: Diamond
2.5
37
Total Internal Reflection
Rays entering more oblique than critical angle don’t emerge from denser medium and reflected back
38
Total Internal Reflection examples
Fibre optic cables, Cornea air interface in eye
39
Total Internal Reflection in eye can be overcome by:
Can be overcome with contact lens with a higher refractive index than eye
40
Wavelength
wavelenght of a wave is the distance between two successive peaks of propagation.
41
One oscillation is
defined as the segment of the wave where it returns to the start, which is also known as one cycle
42
Amplitude
is a maximum displacement of the wave from its baseline.
43
Interference
Interference is the phenomenon where two or more waves interact with one another.
44
Diffraction
Diffraction is described as the apparent bending of a wave around an obstacle.
45
Airy disc
Diffraction through a circular aperture causes a diffraction pattern where there is a central bright disc
46
Airy pattern
Airy disc that is surrounded by alternating light and dark rings, together known as the Airy pattern.
47
How does the size of the aperture affects the size of the Airy disc:
The smaller the aperture the larger the disc. This is because diffraction is most prominent in smaller apertures.
48
Radiant flux measured in?
(measured in watts) is the radiometric equivalent of luminous flux (measured in lumens)
49
A luminous flux measured in?
lumen
50
Luminous flux
Luminous flux is photometric, and quantifies how much light is emitted from a point source.
51
Radiant intensity
Radiant intensity (the equivalent of luminous intensity) considers the intensity of light in a given solid angle.
52
Irradiance
Irradiance (the equivalent of illuminance) is the amount of light falling on a given surface area.
53
Jackson cross cylinder
Sphero-cylindrical lens wherein the power of the cylinder is twice the power of the sphere and of the same sign.
54
Coma
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
4 PD base out prism test is most useful for diagnosing
central suppression scotoma
56
direct ophthalmoscope image is
virtual and erect
57
direct ophthalmoscope magnification
15x
58
direct ophthalmoscope field
2DD
59
Indirect ophthalmoscope magnification
3x or 5x
60
Indirect ophthalmoscope field
8DD
61
Indirect ophthalmoscope image is
Real and inverted
62
Optical radiation lies between
X-rays and microwaves in the electromagnetic spectrum
63
400 – 780
Visible radiation
64
315 – 400
UVA light
65
280 – 315
UVB light
66
200 – 280
UVC light
67
780 – 1400
IRA light
68
1400 – 3000
IRB light
69
3000 – 10000
IRC light
70
Laws Of Reflection (2)
1) Incident Ray, Reflected Ray & Normal all lie on same plane 2) Angle of incidence is equal to angle of reflection
71
Absolute Refractive Index
Velocity of light in VACUMN/velocity of light in that medium
72
Refractive Index
Velocity of light in AIR/velocity of light in that medium
73
Example of refractive index: Flint glass
1.6
74
Total Internal Reflection:
Rays entering more oblique than critical angle don’t emerge from denser medium and reflected back, known as Total Internal Reflection
75
Examples of Total Internal Reflection
Fibre optic cables, Cornea air interface in eye Can be overcome with contact lens with a higher refractive index than eye
76
priSm obeys Snell’s Law
YES RAY passing through prism deviates towards Base of prism IMAGE is displaced towards Apex of prism
77
Position of minimum deviation
Angle of incidence is equal to angle of emergence Specified for plastic ophthalmic prisms i.e prism bars
78
POWER in Prentice position
Power in Prentice position is greater than in position of minimum deviation
79
Therapeutic uses: CD
* Convergence insufficiency * Diplopia i.e small vertical/paralytic squints, decompensated heretrophorias
80
Ophthalmic instruments in which prisms are used:
* Slit lamp * Applanation Tonometer * Keratometer
81
Porro Prism *Can deviate incident ray by 180 *Causes total internal reflection *Image is inverted but not transposed left to right
82
Dove Prism *Rotates image by 180 degree *Image is inverted but not laterally transposed
83
Right Angle Prism *Deviates the incident ray by 90 degree *Also known as reflecting prism *Produces inverted image
84
Risley Prism: *Two prisms in front of each other that can rotate with respect to each other *Measures phoRias!
85
One prism dioptre produces
a linear displacement of 1 cm of an object at 1 m
86
1 PD=
1 PD=1/2 degree
87
converging lens
Biconvex
88
diverging lens
Biconcave
89
Lens
Portion of refracting medium bordered by two curved surfaces which have common axis
90
Convex/Converging Lens: uses
Is used to correct hypermetropia, presbyopia & aphakia * Can be used as low vision aid
91
Concave/Diverging: uses
Is used to correct myopia
92
Dioptric Power Of Lens:
F=1/f2 (F is Dioptric power and f2 is focal length in meters) *Lenses of shorter focal length are more powerful
93
Prismatic power increases
Prismatic power increases in the Periphery of spherical lens
94
Use of non-axial portion of lens to gain a psimatic effect is called
Use of non-axial portion of lens to gain a psimatic effect is called decentration of lens
95
Maddox Rod: type of lens
convex-cylindrical lens
96
Maddox Rod : rod is place at which eye?
right eye
97
Esophoria (uncrossed)
98
Exophoria
99
Hypophoria
100
Hyperphoria
101
Vertical orthophoria
102
Toric Surface
When cylindrical lens is bent, XY becomes an arc, that’s known as Toric surface
103
Principal meridians toric
The meridians of maximum and minimum curvature are called principal meridians
104
base curve toric
The principal meridian of minimum curvature is called base curve
105
Jackson Cross Cylinder
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
Jackson Cross Cylinder: check axis
To check the Axis: the handle is held in line with the axis of trial cylinder (HAA)
107
Jackson Cross Cylinder: check power
To check the power: The axis is held in line with the axis of trial cylinder (AA)
108
Focimeter:
* Measures power and axis of a lens * Green light is used * FoCusIng system has Collimating lens (to make light parallel) and Illuminated target
109
Prismatic Effect Of Lens: formula
P= F x D P is prismatic power, F is dioptric power and D is distance in centimeters
110
Photochromic lens changes its color according to
Intensity of incident radiation Photochromic lens changes its color according to intensity of incident radiation
111
Thickness of Antireflective coating
Thickness of Antireflective coating is 1/4th of incident light, that causes destructive interference
112
Chromatic Aberration:
dispersion of white light into its constituent colors is called chromatic aberration * Decreased wavelength causes more deviation * It’s Independent of refractive index
113
Chromatic Aberration can be overcome by
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

BRUTE FORCE OPHTH PREP PART 1 (10 decks)

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