Key Terms & Definitions

Question 1

Definition of Low Vision

Answer 1

A person with Low Vision is someone who has a visual impairment where it cannot be remedied by conventional spectacles, contact lenses or medical intervention which causes restriction in one’s life.

Question 2

National Assistance Act 1948 Definitions:

Blind/Severely Sight Impaired

Answer 2

‘So blind as to be unable to perform any work for which eyesight is essential’

Question 3

National Assistance Act 1948 Definitions:

Partially Sighted

Answer 3

‘Substantially and permanently handicapped by defective vision caused by congenital or illness or injury’

Question 4

Form for being registered sight impaired

Answer 4

CVI - Certificate of Visual Impairment

Question 5

Leading causes of Sight Loss in the UK

Answer 5

1. Uncorrected Refractive Error
2. AMD
3. Cataract
4. Glaucoma
5. Diabetic Retinopathy

Question 6

Causes of SSI and SI in UK

Answer 6

2. AMD
3. Glaucoma
4. Cataract
5. Retinitis Pigmentosa
6. Diabetic Eye Disease

Question 7

Who can sign a CVI?

Answer 7

Ophthalmology Consultant

Question 8

Classifications of SSI:

Group 1

Answer 8

Visual acuity below 3/60

a px who is 1/18 cannot be certified in group 1

Question 9

Classifications of SSI:

Group 2

Answer 9

Visual Acuity between 3/60 and 6/60 and significant field defect

Question 10

Classifications of SSI:

Group 3

Answer 10

Visual acuity better than 6/60 and a severe significant field defect, especially if in inferior field

Question 11

Other factors considered during registration

Answer 11

How recent the visual impairment occurred
Age of diagnosis
Home/living situation1
Any additional impairments

Question 12

Classifications of SI:

Answer 12

VA of 3/60 to 6/60 with full visual field
VA up to 6/24 with moderate reduction of visual field or with a central cloudiness/blur
VA 6/18 or better with gross field defect (retinitis pigmentosa and glaucoma)

Question 13

Classification for infants and young children

Answer 13

Infant and young children with visual ocular abnormalities are certified SI unless obviously blind.

Question 14

Pathway of registration

Answer 14

1. DO, GP or OO identifies visual impairment and referred to eye clinic.
2. Px seen by Consultant Ophthalmologist who performs tests. If eligible, the official documentation will be given.
3. Signed CVI goes to: Office of National Statistics, GP and local authority.
4. Local social services will contact for confidential registration & registration card
5. Social Care and Rehabilitation Assessment is performed to identify needs and entitlements.

Question 15

Long Cane:

Answer 15

White
Mid-chest Height
Lightweight
Moved side to side in arc of body
Used for mobility
Can be fitted with roller tip
Informs others of impairment
Red portion = hearing impairment

Question 16

Symbol Cane:

Answer 16

White
Light weight
Not load bearing
Often foldable
Carried diagonally across chest
informs others of impairment
Red portion = hearing impairment

Question 17

Guide Cane:

Answer 17

White
Shorter than long cane
Used by Px's with more useable vision
Provides support in unfamiliar environments
Used to find obstacles

Question 18

White Walking Stick

Answer 18

White
Load bearing
Exact length is important
Used for mobility support
Fitted by a professional
Red Stripe = hearing impairment

Question 19

High Reading Addition/Spectacle Magnifiers:

Advantages

Answer 19

Hands free
Very wide field of view
Cosmetically & psychologically more accepted
Wide range available
No specialised equipment training required

Question 20

High Reading Addition/Spectacle Magnifiers:

Disadvantages

Answer 20

Requires prism control for +4.00D and above
Short working distance
More difficult to provide required illuminance
Total powers can be high = more expensive

Question 21

Acuity Reserve

Answer 21

2:1

required N/2 = aimed for N

Question 22

Metre Angle:

Answer 22

How many angles required of convergence for metres

Question 23

‘Rules of Thumb’

Spectacles Mounted Magnifiers

Answer 23

1 Base IN prism per dioptre of object to lens distance

Question 24

‘Rules of Thumb’

High Reading Addition

Answer 24

1 Base IN for every dioptre of ADD over +3.00D

Question 25

Amsler Chart: Structure

Answer 25

Grid of lines making squares Central fixation point Designed to measure central 10 degrees of visual field

Question 26

Amsler Chart: Use

Answer 26

``` Well lit room/in day light Held at 30cm Wear NV correction Each eye occluded in turn Px should stare at fixation point Px should report any lines that are distorted or missing ```

Question 27

Contrast Definition

Answer 27

Contrast is the difference in luminance or colour that makes an object discernible

Question 28

Why is contrast sensitivity measured?

Answer 28

Allows us to gauge visual performance under real world conditions Allows us to predict the likely success of a LVA Allows us to consider whether contrast advice is required/warranted

Question 29

What is Contrast Sensitivity

Answer 29

The lowest amount (threshold) of contrast that can be seen (resolved) by a patient.

Question 30

Three low contrast charts

Answer 30

Pelli-Robson Chart Bailey Lovie Chart VISTECH Chart

Question 31

Pelli Robson Chart

Answer 31

All letters same size Tested at 1m Eight rows 1 row has 2 sets of 3 letters Each triplet of letters have same contrast Contrast reduces in logarithmic progression Contrast reduces across and down the chart Contrast ranges from 89% to 0.5%

Question 32

VISTECH Chart

Answer 32

Five rows Nine columns Sine wave gratings/circular grating patterns Decreases in contrast left to right Increase in spacial frequency top to bottom Forced choice Used at 3m

Question 33

Snellen Chart: Disadvantages

Answer 33

``` Too few letters at lower acuities Non-logarithmic design No consistent ratio between letter size Non consistent spacing = crowding Inconsistent letter legibility Measures high contrast only Does not consider real life environments Designed for use at 6m Over estimates acuity if used at closer WD Does not allow for estimates if mag requirements ```

Question 34

Bailey-Lovie Chart Advantages

Answer 34

Logarithmic in design Constant ratio of letter size Line and letter spacing equivalent throughout Can be used at any appropriate WD Allows more accurate prediction of mag requirements Each line has 5 letters to improve accuracy/reliability Each letter has a score which improves accuracy

Question 35

What is a 'spot task'

Answer 35

Survival task Brief Require little or no fluency Example: pills, bills, cooker dials & cooker instructions

Question 36

What is a 'sustained tasks'

Answer 36

Requires fluency | Example: reading for pleasure

Question 37

Hand Magnifiers: Advantages

Answer 37

Relatively inexpensive Socially accepted Can be internally illuminated Quite portable/lightweight

Question 38

Hand Magnifiers: Disadvantages

Answer 38

Requires dexterity Do not have both hands free Low quality lens Difficult to train & Px to replicate