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Year 3 > Low Vision > Flashcards

Low Vision Flashcards

1
Q

Definition of low vision

A

The WHO defines low vision as visual acuity less than 6 / 18

and blindness as Visual acuity less than 3/60 or a visual field < 10 °

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2
Q

What is Disability Glare

Also known as veiling glare

A

Stray light which interferes with visual performance - normally this glare affects low vision Patients
Predominantly due to scatter and fluorescence in the Ocular media
helped by Suitable filter lenses which reduce shortwave radiation

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3
Q

what is discomfort Glare

A

Stray light which reduces visual comfort,not responsible forreduction in VA

Normally associated with differing levels of illuminance within the visual field
eg -Performing a visual task under bright direct lightening in a room with poor background illumination

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4
Q

Reflectance

A

A ratio comparing the lumens of flux leaving a Surface to the lumens of flux that were incident on the Surface

Symbol = P ( rho)

unit =none as a ratio - maybe given as a %( ratio → % X by 100)

optical Surface

P = ( n’ - n )2( Squared)
——–
n’ + n

non optical Surface

P= 0 leaving Surface
————————–
O incident on Surface

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5
Q

Albinism

2 forms

A

Congenital Condition - lach of pigment or body’s inability to Produce Pigmentation

2 forms
Ocolocutaneous - affect Skin,hair,eyes 1 In 20,000 - VA often worse

Ocular albinism - affects eyes 1 In 40,000 VA often less than 6/ 24
while eyelashes very Pale blue Iris look pink at times - light reflecting of blood vessels
Extreme photophobia,Pendular nystagmus,high refractive error,high with rule of Astigmatism full visual field
no treatment -Improve visual comfort with filters,tints,contact lens
Genetic counseling recommended

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6
Q

Photometry

Luminous Intensity

A

the Power /strength of a Source in a given direction
Symbol l
unit candela (cd)
I = lumens / w ( Solid angle )

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7
Q

photometry mean spherical intensity

A

The average intensity of a real world light Source considered to give out light equally in all directions
m. S.I = O (lumens) / 4 (Pie) solid angle Steridians around point)

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8
Q

luminous flux

A

the rate of light flow from the Source in a given direction

O = I x w

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9
Q

Illuminance

A

The amount of luminous flux falling on a Surface of unit are

Symbol = E unit lux

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10
Q

luminance

A

luminance Symbol L is the amount of light per unit area emitted by a surface in a given direction
luminance = illuminance X reflectance

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11
Q

Reflectance

A

A ratio comparing the lumens of flux leaving a surface to the lumens of flux that were Incident on the Surface
Symbol = P (rho )
unit = ratio= no unit maybe given as % ( x by 100)

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12
Q

luminous effectively

A

How many lumens of flux as Source produces per watt of electricity used

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13
Q

Inverse Square law

A

Illuminance at a Point on a surface perpendicular to a source is Inversely Proportional to the Square of the distance from the Source to the surface
E =I / d2 (Squared) (metres)

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14
Q

cosine law of illumination

A

E = I / d2 x COs O (angle)

the greater the angle between the light Source and the Surface

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15
Q

How many Steradians Surround a point

A

4 (Pie )

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16
Q

What is meant by the luminance of a Surface

A

How bright the surface is to the observer

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17
Q

A60 walt tungsten filament lamp has an efficiency of 12 lumens per watt
calculate
a) luminous flux
b) the mean Spherical intensity ofthe lamp

A

a) 12 lumens X 60 watts = 720 lumens

b) MSI = O / 4 (pie) 720 / 4 (pie) = 57. 30cd

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18
Q

Role of health care practitioner

A

is ( partially) to increase ‘activity and the participation of our patients

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19
Q

Impairments

A

problems in body function and structure Such as a significant deviation loss

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20
Q

functioning

A

an umbrella term for body function and structures it denotes the positive or neutral aspects of the interaction between a persons health conditions and that individuals Contextual factors

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21
Q

Activity limitations

A

Difficulties a person may have in executing activities

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22
Q

Participant restrictions

A

problems an individual may experience in involvement in life Situations

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23
Q

low vision definition

A

the who defines low Vision as visual acuity less than 6/ 18 and blindness as visual acuity less than 3/60 or a visual field < 10 degrees

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24
Q

low vision consensus group 1999

A

A person with low vision is someone who has impairment of visual function for whom full remediation is not possible by conventional Spectacles contact lenses or medical intervention and which causes restrictions in that persons everyday life

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25
Q

Blind

A

So blind as to be unable to perform any work for which eye sight is essential

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26
Q
  • SSl registrants Can be classified into 3 groups
A

Groups 1 visual acuity below 3/60 A Cx who is 1/18 cannot be Certified in group 1
Group 2 Visual acuity between 3/60 and 6/60 and is Significantly contracted field of Vision
Group 3 visual Acuity better than 6/60 and have a Severely contracted field of view especially if in the inferior field

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27
Q

Community care act

A

1948

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28
Q

referral of visual Impairment

A 
RVI form
can be sent from a hospital clinic
informs Social Services
Request assessment
states Urgency
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29
Q

benefits of registration

A 
personal independance Payment (pip)
free or reduced bus fare
free NHS eye exam 
Assesment by Social Services
SI -don't get
tax allowance
TV license reduction
blue badge
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30
Q

Services available multidisciplinary team

A 
low vision Clinic
rehab officers
mobility officer
ECLO 
G.P
occupational therapist
audiology
education officer
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31
Q

role of dispensing optician

A 
Assist in devices - LVA 
non optical aid
correct addition
illumination advice
Discuss pathologies
refer to multidisciplinary 
contrast advice
local charities
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32
Q

How do we measure contrast sensitivity

A

Allows us to gauge visual Performance under real world conditions
Allows us to predictthe likely success of LvA’S
consider weather contrast advice + support needed
calculate contrast reserve+ feeds into our prescribing strategies

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33
Q

Pelli robson- chart

A

All letters same size (2.8 degrees at 1m)
use at 1m
8 rows comprising of 2 triplets of letters
each triplet has Some contrast
Contrast reduces across and down
range 89% to 0.5%

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34
Q

Baily lovie chart

A 
one panel distance acuity
one panel low Contrast
difference in lines gives low contrast sensitivity value
externally illuminated 
100% contrast one side 10% contrast other side
logmar progression 5x4 grid
6 metre 
14 lines of 5 lettersper line
ranging from 0.8 logmar to - 0.5 logmar
53x61mm
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35
Q

vistech chat

A 
Five rows
Nine columns 
Sine wave grating/ circular grating
Decrease in contrast left to right
increase in Spatial frequency top to bottom
used at 3m
36
Q

Rods

A 
Rhodopsin
Scotopic
low acuity
Achromatic
High density away from macula
37
Q

Cones

A 
3 types Red blue green
photopic
High Acuity
Trichromatic 
Central retina / fovea most dense
38
Q

Visual field

A

the extent of the area In space in which object are visible to an eye in a given Position

39
Q

Scotoma

A

An area of reduced / no visual acuity Surrounded by an area of relatively normal vision

40
Q

Absolute Scotoma

A

Blind spot - no photoreceptors

a defect that is present during all Stimulus

41
Q

relative scotoma

A

a defect that Presents when stimulus is weaker

eg reduced contrast Sensitivity

42
Q

negative scotoma

A

A Scotoma that’s not generally percieved by Cx

eg blind spot

43
Q

Positive Scotoma

A

Percieved by the Patient . Such as black spot in vision

44
Q

Hemianopia

A

loss of one 1/2 of your visual field

45
Q

eccentric fixation

A

is the process of rotating the eye so light falls on a different less damaged part ( close to macula)
called PRL Preffered retinal location

46
Q

Steady eye strategy

A

employed by the patient achieving their PRL keeping eye still and moving print
6 weeks training

47
Q

AmsIer chart

A 
Gid of lines making Squares
Central fixation point
Some have diagonal lines to and fixation
designed to measure Central10 degrees of visual field 
well light room
held at 30cm
wear SVN
each eye occluded
stare at central fixation Spot
report any lines distarted or missing ( emergency referral optom)
48
Q

Disadvantages of Snellen chart in LV

A 
Too few letters at lower acities
non logarithmic design
no contrast ratio between letter size
non consistant Spacing
measures high contrast acuity only
designed at 6m
49
Q

advantages baIie lovie chart in LV

A 
logarithmic design
constant ratio of letter size
line  + letter spacing same
any appropriate WD
5 letters per line
50
Q

magnification

A

New RIS / Old RIS

51
Q

BS EN iso 15253

A

British standard which covers Optical devices for low Vision aids

52
Q

estimating mag

A

= Acuity Achieved / Acuity required.

AA / AR

53
Q

Threshold acuity

A

the smallest possible size they can read .

54
Q

fluency

A

As a print Size reduces towards a patients threshold acuity their reading rate reduces

55
Q

Hand magnifiers

advantages

A 
Inexpensive
cosmetically acceptable
can be internally illuminated
Portable lightweight
trained to be used with Spectacles
flexible working distances
56
Q

Hand magnifiers

Disadvantages

A 
requires steady hand
not both hands free
Poor Image quality
effective magnification less than described
needs training due to dynamic System
difficult to change batteries for LV Cx
57
Q

Stand magnification

advantages

A 
very high magnification
can be internally illuminated
Some can tilt
Hands free
adjustable
58
Q

Stand magnifiers

disadvantages

A 
Poor fOv
Increased aberrations 
more conspicuous
most require near correction
requires flat surface
may struggle with body position
59
Q

Bar devices

A 
reading addition
flat Surface tasks
place device directly on task
good FOV
Reducing eye to lens does not effect FoV

Inexpensive
ease of use
cosmetically acceptable
Good FoV

Very limited magnification range
one meridian only - distorts Image

60
Q

stale the formula for and Conditions under which nominal magnification is Created

A

Mnom = Fe / 4
object is @ F 1st principal focus
Image@ infinity

61
Q

state formula for and Conditions under which maximum magnification is created

A

Mnom = Fe / 4 + 1
Vertex distance = O
Image formed RSD - 25 CM ( reference Seeing distance)

62
Q

Contrast

A

is measured of the difference between brightest and darkest Point

63
Q

Distance Telescope

objective lens

A

the lens nearer the object
it is the entrance pupil for telescopes
its diameter controls field of Vlew

64
Q

Distance Telescope

eyepiece lens System

A

the lens nearer the patient
always the highest power lens
Sometimes a Series of lenses which help control aberrations
Position controls field of View

65
Q

afocal

A

A telescope where parallel light enters and leaves the System is referred to as afocal

66
Q

Distance object

Benefits

A 
only realistic option for Dv mag where object cannot be Moved or changed
Good depth of field 
hands free
can be Mono /binocular
can be variable focus
67
Q

Distance telescope

limitations

A 
High cost 
difficult to use
extensive training
Very poor Fov
Heavy
conspicuous 
Require Very accurate Centration
68
Q

Types of telescopes

A

Spotter handheld monocular - hand held non adjustable afocal easier to use,Small
Adjustable handheld Monocular - adjustable tube
Binoculars - wide FOV cheap
Bl optics - Spec mounted on different plane
Spec mounted telescopes

69
Q

calculating magnification

A 
M = - Fe / Fo.   
fe = eyepiece
fo = objective
70
Q

Markings

A

8 X 20 X 7. 5

8: magnification
20: objective Diameter
7. 5: field of View In degrees

71
Q

field of Vlew

A

This is Significantly restricted in telescopes
binocularity Is Important to Improve foV
Improves mobility or fluency and visual Comfort

72
Q

terrestrial telescope

A

astronomical telescope been modified to produce upright Image

73
Q

Distance cap

A

a negative (Concave ) Mounted on the front of a telescope to modify it from near to distance vision

74
Q

Reading cap

A

a positive lens mounted on front of a distance vision telescope to modify for near

75
Q

tele microscope

A

A distance vision telescope being modified for near with use of reading cap

76
Q

free working distance

A

Distance between the most anterior part of System ( front) + object being viewed

77
Q

Exit image Vergence

A

Power of light leaving back of System

78
Q

Explain the stage depression of loss model

Include a minimum of 4 facts

A

lack of engagement with professional
feeling of worthlessness
poor memory
fee lings of hopelessness at outcome

79
Q

How will the patients age in f luence the successful use of low vision aids ( 4 facts)

A

less likely to accept
Dexterity issues
more likely to have additional needs / health issues
difficult to learn new Skills

80
Q

name a non optical aid that may assist Mrs D Seeing the dials on her Cooker

A

Stickers or labels @ N18

81
Q

what is the benefit of testing contrast Sensitivity

A

15 Mark answer- Allows use to Predict the Likely Success of LVAs
Allows us to gauge weather contrast advice Is warrented

5 mark - gauges visual performance in real world.

82
Q

state Criteria for registration as Sight Impaired

A

3/60 → 6/60 full visual field
6/60→ 6/24 moderate field loss
6/18 or better + gross field defect

83
Q

Symbol cane

A

symbol cane - foldable White cane Indicates Visually Impaired -extends Cane and holds diagonally across body or keeps folded and holds across chest
low

84
Q

guide Cane

A

to find obstacles be .. holds guide cane diagonally across your body.and use it to find Sstacks

85
Q

long cane

A

To avoid obstacles you roll or tap It from Side to side as you Walk

86
Q

Red + white Cane

A

low hearing and Vision

Year 3 (8 decks)

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