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Low Vision > Final Exam Part 2 > Flashcards

Final Exam Part 2 Flashcards

1
Q

US and Canda Definition of blindness

A

20/200 or worse or 20/125 or worse on logMar. Greatest VF less than 20 degrees with goldman III4e.

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2
Q

US and Canada Definition of VI

A

20/70 or worse.

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3
Q

Visual Impairment

A

A functional limitation of the eye

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4
Q

Visual Disability

A

A limitation of the abilities of the individual

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5
Q

Visual Handicap

A

A limitation of personal and socioeconomic independence

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6
Q

Main cause of blindness

A

ARMD (in developed) Cataracts (in undeveloped) Glaucoma, DR.

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7
Q

_____ of kids with VI are multiply handicaped

A

75%

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8
Q

Central Vision loss causes

A

Hereditary macular dystrophies, ARMD, foveal hypoplasia (Aniridia, Albinism)

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9
Q

Peripheral Vision Loss

A

RP like dystrophies, glaucoma, CVA, TBI.

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10
Q

Central and peripheral vision loss

A

ON conditions, late stage dystrophies, DR, ROP

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11
Q

Conditions with photosensitivity

A

aniridia, albinism, achromtopsia, Retinal dystrophies, corneal scar/dystrohies, congenital glaucoma.

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12
Q

Conditions with color vision changes

A

achromtopisa, cone dystrophies, ON disease.

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13
Q

Conditions with contrast changes

A

cataracts, glaucoma, retinal dystrophies, corneal dystrophies/scarring.

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14
Q

Conditions with Nystagmus

A

Any early onset diseases affecting the foveal pathway

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15
Q

VA when don’t need LV but maybe an add

A

20/100 or better (kid) or 20/50 (adult)

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16
Q

LV when need magnification 2-5X

A

20/100-20/250 (kid) or 20/60-20/100 (adult)

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17
Q

Need LV devices

A

20/300-20/800 (kid) or 20/100-20/400 (adult)

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18
Q

Brail use

A

20/1000 (kid) or 20/400 adult.

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19
Q

What does VI impact in a child’s development

A

Gross and fine motor skills, cognitive develop, socialization and communication.

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20
Q

Walking age for VI child

A

18-24 months (normal is 9 months)

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21
Q

Fine motor development in VI

A

Vision leads tactile exploration and vice versa so it is delayed.

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22
Q

Language acquisition in VI

A

Have the same rate of language development but their development of descriptive language lags.

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23
Q

Those with _____ VI complain of decreased hearing ability

A

acquired.

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24
Q

Conceptual issues with VI

A

colors, entire object in 3D, figure ground, size and shape.

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25
Q

Who with VI is most likely to suffer from literacy

A

Moderate (20/100-20/400)

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26
Q

Bioptic Driving laws

A

20/70-20/200. Daylight driving.

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27
Q

Why would adults need higher magnification than predicted based on VA

A

Hard for them to find a new preferred foveal locus.

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28
Q

VA that leads to good prognosis with LV device

A

20/800 or better

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29
Q

Do you trial frame with a phoropter

A

NO! use a trial frame. Allows for vertex distance and eccentric viewing.

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30
Q

Which axis should you scope?

A

Patient’s axis of fixation

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31
Q

JND equation

A

(denominator)/100

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32
Q

Prescribing for near

A

Need 2x magnification above threshold for comfortable viewing.

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33
Q

How to use an add for pre-oresbyope?

A

Use RDM. They get closer. Plus lens will barely do anything. Will just make them more comfortable. No WOW factor.

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34
Q

Contrast threshold

A

The lowest threshold the patient can recognize optoptypes

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35
Q

Contrast reserve

A

The ratio of contrast of object to contrast threshold.

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36
Q

Most people CT

A

1-3% of the acuity demands of reading material so contrast reserve 20/1 or 30/1

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37
Q

What contrast reserve will the patient have difficulty

A

below 10/1

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38
Q

Bailey Lovie charts

A

10% contrast and 90% contrast with change in optotype size. Normal difference is 2 lines. Drop of 4 lines is significant.

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39
Q

Peli-robinson

A

Perform at 2x threshold. Functional defficeins with CT is 5% or greater.

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40
Q

Which CT is better

A

Bailey Lovie better for early dystrophies and things like cataracts. Peli can be used on LV patient.

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41
Q

How to help BV in young children

A

Add with BI prism

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42
Q

Stereo test to use on LV

A

Local test. Very rarely get global.

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43
Q

Testing VF in LV

A

Can use goldman or 24-2 or 30-2.

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44
Q

Confrontation VF

A

Finger wiggling works the best.

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45
Q

Tangent Screen and Campimeter

A

Test with 9mm whit stimulus at 1 m. Next test 18 mm target at 2 m. The field should expand to twice the original size. Failure to expand is nonphysiolgoical.

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46
Q

Testing bulls eye lesion with macular lesion

A

tell them to center their blindspot over the target.

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47
Q

Lesion in relation to PRL

A

If to the right make it hard to saccade when reading. If to the left make it hard to saccade to beginning of line.

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48
Q

VA is technically a measure of ____ but is described in ____ terms

A

angular, linear

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49
Q

Types of VA in increasing difficulty

A

detection, resolution, recognition, hyperaciuity.

50
Q

Levels of VA documentation

A

NLP (or total blindness), LP w/o projection, LP with projection, VA.

51
Q

Do you take into account EF when measuring?

A

NO! Look at their central vision.

52
Q

VF determination for LV

A

Widest diameter VF is 20 degrees or less or -22 DB of worse mean deviation on automated

53
Q

VF determination for VI

A

Visual field loss in the periphery (such as glaucoma or RP) or in a sector.

54
Q

Hyperacidity typical threshold

A

3-8 arc seconds

55
Q

Resolution typical threshold

A

1 arc minute

56
Q

What does a better hyperacidity than a resolution in LV indciate

A

There is some macular function left.

57
Q

Coding with LV

A

Code for medical or pathological conditions, Code for legal blindness, and then anything after

58
Q

Code for legal blindness

A

H54. 8

59
Q

logMar Distance

A

Either 4m or 6m. Most often 4m though.

60
Q

Variation of LogMar based on lines and letter

A

Each line varies by 0.1 and each letter by 0.02.

61
Q

Fein bloom chart

A

Calibrated for feet. Can get as close at 2-3 feet.

62
Q

FrACT

A

A computer based test where you have to indicate the position of landolt C’s. Can get as low as Feinbloom chart.

63
Q

BRVT

A

Goes from tumbling E’s to grating to b and white pair.

64
Q

Standards for contrast

A

Background luminance by 80-320 and characters be no more than 15% of the background luminance.

65
Q

What does increased VA with color contrast indicate

A

The need for tinted spectacles.

66
Q

Landolt C’s can by ____ better than other optotypes

A

20-25% as it is resolution and not recognition.

67
Q

What does snellen fraction mean

A

The denometer is the distance that the target subtends 5 arc min.

68
Q

1/2 JND

A

Sphere bracketing lens, cya test lens, crossed cylinder lens

69
Q

full JND

A

Cylinder bracketing lens

70
Q

Angular subtense of MAR

A

5 times the MAR

71
Q

Preferred method for recording VA

A

M notation

72
Q

Point

A

1 point is 0.353 mm

73
Q

Point to snellen

A

Multiple pt by 6.25

74
Q

Recommendations for testing vA

A

Binocular and then better eye.

75
Q

Spectacle plane

A

12-15 mm from cornea

76
Q

Keplerian

A

Two positive lenses with focal spots corresponding.

77
Q

Galilean

A

Objective is positive and eyepiece is negative.

78
Q

LIM

A

w image/w object or 1-du/1-dv

79
Q

RDM

A

uref/uaided

80
Q

RSM

A

y2/y1

81
Q

Telescope LIM

A

1/1-tFobj.

82
Q

How to predict Near VA

A

From Far VA

83
Q

Near viewing with high or irregular astigmatism

A

Can be increased VA at near due to increased DOF

84
Q

Predicting Near VA in M notation

A

(MAR)uref or (VA)RDM

85
Q

Predicted add to read 1 M print

A

1/far VA

86
Q

Predicted add for any demand

A

1/far va (1/actual demand)

87
Q

RIM

A

Measured VA/Demand

88
Q

Magnification value on telescopes

A

NOT RIM

89
Q

Equivalent dioptric value

A

the value that allows the comparison of different magnification devices

90
Q

Principal plane of plano convex lens

A

Vertex of the convex surface

91
Q

Principal plane of biconvex

A

midpoint of front and back lens

92
Q

Gaussian Equation

A

Feq=F1+F2-t/n(F1F2)

93
Q

Calculating power from lens clock

A

FT=FC(Nt-1/NC-1) NC=1.53 or 1.56

94
Q

Finding Feq by measuring image formed

A

1/distance

95
Q

Finding Feq by measuring image sizes

A

y2(u/y1). u must be greater than v and greater than 4 times y1.

96
Q

Systems that do incorporate Ametropia, accommodation, or add

A

Feq=F1+F2-DF1F2.

97
Q

Myopic RE is

A

+

98
Q

Hyperopic RE is

A

-

99
Q

If a device is held in the spectacle plane what does the LIM equal

A
  1. Only helps with the working distance. so RIM=RDM
100
Q

RIM of a LV device when V=0

A

RIM=FeqX-uref

101
Q

RDM

A

Ref/uaided or Feq X -uref

102
Q

When is RIM constant?

A

When V=0

103
Q

Maximum equivalent power of an add

A

When d=0

104
Q

When d=fdevice

A

then the add will not contribute to Feq.

105
Q

When d>Fdevice

A

Then Feq will be less than Fdevice

106
Q

ER

A

Feq=ERX F add

107
Q

EVD

A

Where we would have to place an object to subtend the same angle as the virtual image. ER=d-v/ER

108
Q

Predicted VA

A

EVD X Initial VAm/initial viewing distance

109
Q

FOV

A

A/d(EVD) or A/D(feq)

110
Q

FOV when working distance equals focal lenghth

A

FOV equals the aperture size regardless of the image distance.

111
Q

When does FOV incresase

A

when working distance is greater than focal length and image mergence is non zero

112
Q

Effective magnifiaction

A

F/4

113
Q

Conventional magnification

A

F/4+1

114
Q

Largest value that binocular vision can occur

A

+10D

115
Q

Advantages of high plus spectcles

A

Largest FOV as close to spectacle plane.

116
Q

Disadvantages of high plus spectacles

A

Fixed lens position poor for patients who use eccentric viewing. Writing is difficult if add greater than 10.

117
Q

When should you do single vision reading prescription

A

If add more than 3.50D

118
Q

Hand magnifiers advantages

A

Greater working distance, good for eccentric viewing,

119
Q

Hand magnifiers disadvantages

A

Reduced FOV, Must use correct working distance

120
Q

Guidelines to prescribe hand magnifers

A

Should minimize working distance and view through distance correction,

121
Q

Freestanding devices advantages

A

Normal reading distance, good for short tasks,

122
Q

Distanvatges to freestanding devices

A

smallest FOV, Aberrations is viewed at an angle. Patient must accommodate.

Low Vision (4 decks)

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