Brainscape's Knowledge GenomeTM

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


See full index

written boards > Optics > Flashcards

Optics Flashcards

0
Q

Prentice rule

A

PD=h*D

h (cm)
D diopter of lens power

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

Vergence

A

U+V=D

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

Focal length

A

1/D=f

D= dist to object in m

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

Spherical equiv

A

Sphere+1/2cyl

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

Transverse mag

A

Image dist/obj dist

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

Axial mag

A

M transvrse^2

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

Simple magnifier

A

D/4

D= dioptic pwr of lens

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

Spectacle lens magnification

A

Mag=2% per diopter of pwr

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

Magnification of a telescope

A

Deyepiece/Dobjective

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

Refracting power of a spherical surface

A

D= n’-n/r

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

Power of a thin lens immersed in fluid

A

Dair = nIOL-nAIR
——- ————
D aqu. nIOL-nAQU

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

REFLECTING power of a spherical mirror

A

Dreflecting= 2/r

r= radius of curvture

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

SRK formula

A

A-2.5(axl)-0.9K

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

In lens prob if image is + and is on other side of lens it is….

A

Real and inverted

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

In lens prob if image is - and forms on left side it is…

A

Virtual and upright

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

In schematic eye how far is K from nodal point?

A

5.5mm

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

In schematic eye how far is nodal point to the fovea?

A

17mm

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

In schematic eye, what is the axial length of the eye?

A

22.5 mm

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

In schematic eye, whats the diameter of the ON?

A

1.7 mm

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

Whats the refractive index of the cornea?

A

1.37

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

Whats the refractive index of air

A

1

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

Whats the refractive index of aqueous?

A

n=1.33

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

How much arc does the 20/20 E subtend?

A

5 min of arc

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

What’s the radius of the corneal curvature in meters?

A

r=0.07m

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

How many min of arc does a 20/200 letter subtend?

A

50 min

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

How tall is a 20/20 letter?

A

9mm

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

What does laser stand for?

A

Light amplification by stimulated emission of radiation

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

what do you worry about w hyperopic shift?

A

orbital tumor

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

focal length?

A

f=1/D

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

What kind of mirror is a shaving mirror?

A

concave

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

reflecting power of a mirror

A

Drefl=1/f=2/r

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

when you use u+d=v and the answer is -, what does that mean in terms of real vs virtual etc

A

if its negative then its VIRTUAL AND UPRIGHT.

In a lens problem it to the left and in a mirror problem its to the right

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

how do you fix diplopia in anisometropic glasses?

A

put a “slab-off” prism on the more minus lens

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

whats placido disc keratometry?

A

looks like an ophthalmoscope projects rings onto the K gives a sense of irregular astigmatism

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

if you see scissoring on retinoscopy whats the dx?

A

kcn

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

what are the 5 steps in calculating rigid lens power?

A

1) chose a BC +0.50 steeper than low K value
2) convert rx to minus cyl form
3) drop the cyl
4) convert to zero vertex distance
5) subtract +0.50 from final value

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

how do you solve vertex distance questions?

A

1) understand that the glasses rx is not the refactive error of the eye!
2) find FP from the glasses and add the vertex dist- that’s the true fp of the eye
3) find reciprocal of that dist to find real D error of eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what’s constructive interference?

A

two light waves from SAME LIGHT SOURCE are added together (laser?)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

whats destructive interference?

A

two light waves from SAME LIGHT SOURCE cancel each other out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

whats coherence?

A

the ability for two light waves or two parts of the same beam to produce interference (ie to interact w each other)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

whats diffraction?

A

a light wave bends when it encounters an obstruction or apperture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what types of wavelengths diffract most?

A

long wavelengths

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

how does violet light behave in terms of refraction and diffraction

A

short wavelengths are refracted more and diffracted less

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what phenomenon causes the sky to be blue?

A

scattering (blue is scattered, the rest of the wavelengths are diffracted)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

whats the refractive index of the cornea?

A

1.376

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

a pt will feel comfortable using how much of their accommodative amplitude?

A

1/2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

whats compound myopic astigmatism?

A

both images fall in vit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

whats simple myopic astigmatism?

A

1 image falls on retina 1 falls on vitreous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

whats mixed astigmatism?

A

one image in vit, one image behind retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

how do you make a CL fit tighter (2 options)

A

1) decr BC

2) incr diameter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

what does angular magnification refer to?

A

magnification of SIMPLE MAGNIFIERS ie just divide by 4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

how do you know what size aciol to put in?

A

take horizontal white to white and add 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

how can you help anisometropia in glasses without cl? hint: reduce everything

A

a) reduce central thickness of the lenses
b) reduce vertex distance- bring glasses closer to face
c) reduce the front surface power of the lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

what type of telescope is the operating microscope? kepler or galileo?

A

kepler (then theres a built in prism that flips the image)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

whats the critical angle for total internal reflection of the K?

A

46 degrees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

geometric optics deals w light as a…

A

ray

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

quantum opics deals w light as a…

A

photon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

physical optics deals w light as a…

A

wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

whats the visble light spectrum (what nm to what nm?)

A

400-700nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

whats infrared spectrum what wavelength?

A

> 700 (longer than red)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

what wavelength is ultraviolet?

A

<160 (much shorter than violet)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

whats interference?

A

when 2 rays of light are brought togther

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

whats destructive interference?

A

when 2 waves brought together and the intensity is minimized

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what does coherence mean?

A

the ability of 2 light rays to make interfernce

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

in what direction are sunglasses polarized?

A

vertival slats, so any horizontal waves are blocked (light reflected off water is mostly horizontal)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

what type of wavelength diffracts (ability to bend around edges) more?

A 
longer wavelengths (like red)
think long stretch Armstrong bending around corner
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

whats brewsters angle?

A

the angle at which only 1 part of light that is polarized can be completely transmitted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

when/how does scattering occur?

A

when light hits an irregularity in its path, it scatters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

what are K edema, tindall effect and halos real life examples of?

A

scattering of light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

whats the unit of photometry (light in units based on the response of the eye?)

A

candela

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

whats luminence?

A

amount of light emited by a surface measured in APOSTILLBS. real world example is GVF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

whats the wavelength of yag and what spectrum is it in?

A

1064- infrared

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

whats the wavelength of argon green

A

514

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

do convex mirror act like + or - lenses?

A

minus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

do concave mirrors act like + or - lenses?

A

+

75
Q

whats the circle of least confusion

A

it represents the best overall focus of a spherocylindrical lens

76
Q

what the conoid of sturm?

A

the complicated geometric envelope of light rays emanating from a spherocylindrical lens. The middle of it is the circle of least confusion

77
Q

if a Maddox rod is held horizontally in front of you, how do you see the line?

A

vertical red line

78
Q

why does nighttime exacerbate myopia?

A

bc pupil is big, light comes through all parts of cornea and causes spherical aberration (light from the steeply curved part of K gets focused anteriorly in the vitreous)

79
Q

what test uses chromatic aberration?

A

duochrome (blue falls in vit, red falls behind retina)

80
Q

whats the optical axis of the eye?

A

the line that best approximates light passing thru K, puil, lens and fovea

81
Q

whats the pupillary axis?

A

imaginary line passing through K and exact center of pupil

82
Q

whats the visual axis?

A

line between target and fovea

83
Q

how does pupil size affect depth of focus?

A

smaller pupil gives better depth of focus

84
Q

what is the diameter of the pinhole?

A

1.2mm

85
Q

using a PH sc is only good for what refractive errors?

A

-5 to +5

86
Q

how tall is a 20/20 E?

A

8mm

87
Q

how is amplitude of accommodation expressed?

A

in D

88
Q

how is range of accommodation expressed?

A

in mm

89
Q

whats “emmitropization” of the eye?

A

the phenomenon that as a kid’s eye grows, it doesn’t become hugely myopic! the K actually sheds power so that the eye remains emmetropic

90
Q

during retinoscopy for astigmatism, how do you know if you found the axis?

A

the reflex appears narrowest

91
Q

whats the ideal add segment for hyperopes?

A

round top- decr image displacement but incr jump

92
Q

whats the ideal bifocal seg for myopes?

A

flat top- decr jump and displace

93
Q

how do you use press-on prisms

A

in one direction in 1 eye or you can out it the opposite direction in the other eye

94
Q

whats the best way to correct for prismatic effect of anisometropia?

A

slab-off prism (aka bicentric grinding)

95
Q

how do scl change the ability to accomodate

A

myopes have less ability to accommodate

hyperopes have more ability to accomodate

96
Q

what type of cornea gets high BC?

A

flat K

97
Q

How do you create a looser fit with a scl?

A

1) make BC flatter (incr BC #)
2) Decr the diameter (less of a suction cup)
3) decr the saggital depth

98
Q

where do you measure white to white?

A

across horizontal cornea

99
Q

how close to accurate does an iol with power <25D have to be?

A

within 0.4D

100
Q

whats 2 example of a diffractive multifocal iol and how does it work?

A

reSTOR and technis multifocal IOL

back surface is like Fresnel prisms

101
Q

IOL 25-30 diopters how close to accurate does it have to be?

A

0.5D

102
Q

IOL >30D how close to accurate does it have to be?

A

within 1 diopter!!

so if you have a supershort eye youre screwed

103
Q

whats the Q factor of the human cornea (the difference between central and peripheral K)

A

-0.26

104
Q

whats the definition of angle kappa in optics terms?

A

the difference between the visual axis and the pupillary axis

105
Q

whats the mag of the eye when using a direct?

A

15x (60/4)

106
Q

what part of the slit lamp is made of an astronomical telescope?

A

the eyepiece (theres a prism that flips the image to upright)

107
Q

what part of the slitlamp is a Galilean telescope?

A

the mag fxn (knob or flip thingy)

108
Q

how does the image of the retina appear with a contact lens (tucker style)

A

minified upright

109
Q

whats the diameter of the tonometer?

A

3.06mm

110
Q

how does specular microscopy work?

A

its a reflection of the interface of the endothelium and the aqueous

111
Q

how does a keratometer work? what does it measure?

A

it measures REFLECTING power (and infers refracting power)

112
Q

what does placido disc measure

A

K topography (steepness only)

113
Q

whats the A scan measure

A

TIME it takes for the sound wave to bounce back (looks like series of spikes) can be used to measure EOM thickness in TED

114
Q

How does the laser inferometer work?

A

projects 2 light beam through dense cataract to macula, pt tries to discern 2 light beams

115
Q

whats a brightness acuity tester?

A

looks like a small GVF dome, tests pt with cataract by glaring them w a dome of light

116
Q

whats the WHO definition of legally blind

A

1) BCVA better eye of 20/200
or
2) field in better eye 20 degrees or less

117
Q

how do blind pple deal w scotomas?

A

perceptual completion- the brain fills in missing parts of image

118
Q

a pt with a scotoma is able to utilize an eccentric point of the retina for fixation, whats that called in optics terms?

A

preferred retinal locus

119
Q

at what dist and w what chart is Va tested in low vision pple?

A 
10 ft
ETDRS chart (has more low vision lines)
120
Q

how do you determine add for a blind person? (kestenbaum rule)

A

take the inverse of the Va (ex 400/20 = 20)

121
Q

what should you incorporate into glasses for super blind pple?

A

BI prism to bring eyes in

122
Q

whos not a good candidate for handheld magnifier?

A

parkinsons, RA,

123
Q

whats a stand magnifier?

A

a bulky thing you plop down on top of your newspaper

124
Q

how should pple w low vision set up lamps in their house?

A

most illumination with least glare possible

125
Q

How will a thick lens change the dioptric pwr of a lens?

A

will reduce the power

126
Q

how much angular mag will be created if the image is virtual?

A

none

127
Q

how do you calculate the K for a post-lasik pt if no historical data- do hard pmma lens refraction?

A

K= BC + Rcl - Rbare

K= K power
B= BC of hard PMMA ie the K
Rcl- refraction w cl on
Rbare= refraction with CL off

128
Q

how do you calculate the K for a post-lasik pt if no historical data- do hard pmma lens refraction?

A

K= BC + power cl+ Rcl - Rbare

K= K power
B= BC of hard PMMA ie the K
Rcl- refraction w cl on
Rbare= refraction with CL off

129
Q

who inserted the first IOL (in 1949)

A

Ridley

130
Q

how can hard CL damage the K?

A

causes central epithelial edema

131
Q

what can SCL cause on the k?

A

micropannus

132
Q

diffraction sets a limit on visual acuity when the pupil is less than what size?

A

2.5mm

133
Q

whats the wetting angle of a cl?

A

the degree to which water beads on the surface

134
Q

0.13 meters = how many mm?

A

130mm

135
Q

given lens +2, how do you find focal length?

A

d=1/f therefore f= 1/d
1/2
0.5m

136
Q

how many decimal points do you move over for meter to centimeter?

A

2!!!!

137
Q

how many decimal points do you move over for conversion from meter to millimeter?

A

3!!!!

138
Q

if u+v+d if the answer is - then what does the image formed look like, and where does it fall in a lens problem vs a mirror problem?

A

if the answer is (-) then its virtual and upright!
in a lens question it goes to the left of the lens
in a mirror problem it goes to the right of the mirror

139
Q

an angle of 20 dgrees corresponds to how many PD?

A

40

Double the angle (unless its >20)

140
Q

an angle of 45 degrees corresponds to how many PD?

A

100

141
Q

in a pt with 20/100 vision can you use a +/- 0.25 D Jackson cross?

A

no! too weak

must use a 0.75 or 1D Jackson cross

142
Q

how do you make a Jackson cross cylinder?

A

the sph equiv of the rx = 0

143
Q

if given BC in RGP problem, for every 0.05mm difference between the K reading and the BC you should do what?

A

0.25D/0.05mm
if flatter add plus
if steeper add minus

144
Q

each clock hour is how many degrees in astigmatism?

A

30 degrees

145
Q

how do you calculate post-op lasik K given pre-op refraction and Ks?

A

0.8 * starting refraction

then take that number and subtract from the avg starting K

146
Q

indirect ophthalmoscop works like what type of telescope?

A

kepler (+20 lens of held lens and +60 lens of eye)

147
Q

using a direct ophthalmoscope on a +10 hyperope, whats the mag?

A

acts like +50 mag (less condensing bc hyperopic) is 12.5

148
Q

what type of telescope is the fundus camera?

A

kepler (the camera is plus lens and the eye works as the other plus lens)

149
Q

if pt has a small pupil what things you can change on the indirect?

A

1) move your eyepieces further apart (decreases the EFFECTIVE pupillary distance)
2) bring triangular mirror closer to YOU
3) increase the distance between you and the pt

150
Q

when prescribing high + add, what else do you have to give pt in his glasses?

A

give BI prism if add is >+4
give 2 PD greater than the reading add
ex: giving +8D add you should also give 10PD BI prism in each eye

151
Q

how can you improve low vision in a pt w homonomous hemianopsia

A

give them prisms with the base toward the hemianopsia

152
Q

whats 1/1.5? (multiply top and bottom by 2 = 2/3)

A

0.66

153
Q

whats 0.5/1.5 (multiply top and bottom by 2= 1/3)

A

0.33

154
Q

how do you calculate the power of piggyback lens?

A

hyperopia- 1.5*refractive error

myopia- 1*refractive error

155
Q

whats the most vertical phoria that can be tolerated by anyone?

A

2 PD

156
Q

What type of scan is best for measuring choroidal melanoma height?

A

a scan

157
Q

whats the term that means the most amount of hyperopia and eye can take wo blurring the image?

A

manifest hyperopia

158
Q

whats the term for the minimum hyperopic correction needed to see clearly?

A

absolute hyperopia

159
Q

whats the term for cycloplegic hyperopia-manifest hyperopia?

A

latent hyperopia

160
Q

whats spatial coherence?

A

when 2 parts of the same wave can produce interference

161
Q

whats temporal coherence?

A

when 1 beam of light produces interference with itself

162
Q

whats the definition of power in phaco?

A

the length that the phaco tip can travel relative to overall length

163
Q

whats cavitation in phaco

A

when the phaco tip forms bubbles which breaks down lens

164
Q

whats load in phaco?

A

the amount of lens in contact w the phaco tip

165
Q

what 2/3?

A

0.66

166
Q

whats 1/5

A

0.2

167
Q

whats 1/6

A

0.16

168
Q

whats 1/7

A

0.14

169
Q

whats 1/8

A

0.12

170
Q

whats 1/9

A

0.11

171
Q

whats 1/15

A

0.066

172
Q

how could you see polarized light?

A

wear polarized glasses and look at blue background (ie sky)

173
Q

you give a pt more cyl than hes used to, what can you do to help him adjust?

A

1) turn axis more toward 90/180
2) decrease vertex distance
3) grid cyl onto back of lenses
4) decrease power of the cyl

174
Q

how does giving a child w XT myopic glasses help?

A

makes the eye more hyperopic (image falls behind retina) they have to accommodate/converge/bring eye in

175
Q

how many D of accommodation do you lose every 4 years?

A

1D

176
Q

in HCL questions if given radius of K how to adjust?

A

for every 0.05mm adjust by 0.25D

177
Q

which is the best iol formula for long eyes?

A

srk/t

178
Q

which is the best iol formula for short eyes?

A

hofferQ

179
Q

SPK at 3 and 9 o clock indicates tight fitting XXX cl

A

RGP

180
Q

how will a spherical lens focus incoming light rays?

A

blur circle

181
Q

amplitude of accommodation is what?

A

near point (D) - far point (D) IT IS NOT THE NEAR POINT

182
Q

If you mess up axial length, which types of eyes are more effected?

A

short eyes

183
Q

lensmeter works based on what principle?

A

badal principle

184
Q

when a lens is submerged in water what happens to power?

A

becomes less powerful. careful if its half in air vs totally in water

185
Q

what should be the power of the trifocal portion of glasses?

A

1/2 the add

written boards (13 decks)

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