the definitions and demographics of low vision
TRANSCRIPT
The Definitions and Demographics of Low Vision
• Low Vision
• Partial Sight
• Visual Impairment
Reduced VA which even with the best optical correctionprovided by regular lenses still results in a visual performanceon a standardised clinical test which is less than that expectedfor a patient of that age.
• impairment
• disability
• handicap
The reduction in performance to below normal levelson some standard test of visual function.
The lack, loss or reduction in the ability of a person toperform some task
The fact or the feeling that a patient is placed at some disadvantage in society and cannot live their life as theymight expect.
Visual
Disorder
Visual
Impairment
Visual
Disability
Visual
HandicapOcular disease Functional
changesVisual skills &
abilities
Social consequences
cataract Disability glare Night driving problem
Loss of independence
Glaucoma Peripheral field loss
Mobility problem
Loss of independence
ARMD VA loss
central scotoma
Reading problem Loss of earning potential
Defining Low Vision
a) Visual impairment
b) Visual disability
- Based on performance in a standard test
- Where should the pass/fail boundary be set?
- Based on some measure of performance in a functional task
- Very difficult to quantify such problems
Legal Blindness
Most developed countries have social care systems which Provide benefits and care to certain groups.
Registration is usually necessary in order to be eligible.
Registration is undertaken in order to:
• assess what health and social work resources will be needed for the number of visually impaired people in aparticular area.
• act as the patient’s passport to appropriate welfare benefits.
Therefore some legal definition of blindness is required.
There are problems in achieving a consistent definition ofBlindness.
- WHO (1966) identified some 65 different definitions of blindness.
- some countries (e.g. UK) have dual categories of partialsight and blindness.
The Registration System in the UK
Blind Persons Act 1920
Legislated to provide welfare facilities for the blind.
Provides a definition of blindness which establishes eligibility.
(the partial sight category was added via the National Assistance Act 1948)
Blind - ‘so blind as to be unable to perform work for which eyesight is essential.’
Partial Sight - ‘substantially and permanently handicapped by defective vision caused by congenital defect, illness or injury.’
There is obviously much scope for interpretation with this kind of definition therefore attempts have been made to quantify the degreeof impairment:
Blind - 3/60 or worseor, 6/60 or worse with markedly restricted fields
Partial Sight - 3/60 – 6/60 with full visual field or, 6/24 or worse with moderate field constrictionor, 6/18or better with gross field defect.
The BD8 form
Patients can only be registered by an ophthalmologist who completes a BD8 form (BP1- Scotland, A655 – N.Ireland).
Record of Examination to Certify a Person As Blind or Partially Sighted
Advantages:
• increases in tax allowances• reduction in TV licence• free General Ophthalmic Services• VAT exemptions on products designed for the disabled.
Legislation Relating to Low Vision
The National Assistance Act 1948
Section 26 lays down the responsibilities of the local authority forthose registered as blind and partially sighted.
Additional to the Blind Persons Act 1920
• keeping registers of blind and partially sighted
• providing a social work service, advice and support for those living at home or elsewhere
• making available facilities for rehabilitation and for adjustment to the disability (e.g. teaching Braille).
• providing facilities for social, recreational, occupational and cultural activities
The Chronically Sick and Disabled Act 1970
Dictates that an even wider range of services to be offered by the local Authority:
• practical help and home adaptations
• supply of radio/television
• installation and rental charges for telephone
• meals in the home or elsewhere.
The National Health Service and Community Care Act 1990
Legislates to provide those people with visual impairments with care servicestailored to their own individual needs.
A ‘care plan’ is devised which describes the unique requirements of the particular individual.
If a need is identified which the local authority does not have the staff to providethen it is required to buy in the services
Demographics of Low Vision
The World-Wide demographics of Low Vision
The Global distribution of Blindness
Region Cataract Trachoma Glaucoma
Oncho-
Cerciasis Others
TOTAL
(millions)
Europe, USA, Japan, NZ
Former Communist European states
Latin America & Caribbean
China
Middle East
Other Asia & Islands
India
Sub-Saharan Africa
3.5
8.3
57.7
32.3
45.2
39.9
57.5
43.7
0
0
6.9
17.5
25.7
23.5
9.7
19.4
7.5
6.7
7.9
22.6
5.7
16.8
12.8
12.0
0
0
0.1
0
0
0
5.1
0.9
89.0
85.0
27.4
27.6
23.4
19.8
20.0
19.8
2.4
1.1
2.3
6.7
3.6
5.8
8.9
7.1
Total (% of total blind) 41.8 15.5 13.5 0.9 28.3 37.9
% blind from
Major causes of Blindness World-wide
Cataract 42%
Trachoma 15.5%
Glaucoma 13.5%
Onchocerciasis 0.9%
Others 28.1%
The UK Perspective
Demographic information on low vision can be taken from 3 sources:
1. Low Vision Clinics
2. Blindness Registration Data
3. Disability Questionnaires
There are difficulties with each of these sources.
Blind Year Partially Sighted
126, 830
136,200
149,670
1988
1991
1994
79,050
93,780
115,710
The total number of those registered as blind and partially sightedIn the UK.
Registration (via BD8)
- Avoidance of social stigma
- Poor appreciation of low vision
- Voluntary
Result
Under registration
According to an RNIB study (Bruce et al., 1991) x 4 morePeople are eligible for registration
0-14 15-34 35-54 55-64 65-74 75-84 85+0
5
10
15
20
25
30
Female
Male
Age group (years)
Per
cent
age
Elliot et al., (1997) Invest Ophthalmol & Vis Sci
Age profile of Px’s who visit low vision clinics
Of the 4,744 Pxs seen in this study
- 71% > 65
- 55% >76
- the majority of these elderly people were females
- 57% of the elderly also had other functional impairments e.g. hearing, mobility etc.
- in addition to the primary cause of visual impairment the Pxs frequently had secondary ocular problems the most common of which was cataract.
20
50
80
0-17 18-49 50-64
65-74
>75
Registration Figures for England in 1994
0
10
30
40
60
70
Age Group
Blind
Partially sighted
65-74
Per
cent
age
of T
o ta l
ARMD75.49%
Other10.39%
Glaucoma 6.01%
Diabetic ret. 4.57%
Cataract 3.53%
Major causes of Blindness in the UK in > 65yrs
Actual & Projected increase in population > 85 yrs
Comparisons
The role of the Optometrist
Early detection of pathology
If impairment is not avoided then will be involved in the assessment and prescription of an appropriate Low Vision Aid(LVA).
magnifiers (hand, stand, flat field etc.)telescopesspectacle microscopesand so on.
Personal reading 75.17%
Daily living activities
14.45%
Other7.32%
Watching TV 3.06%
What do Pxs want from a low vision examination?
Visual Impairment % of blind population
Absolute blindness (NPL)
Perception of light
Perception of light with detection of direction
6/240
6/240 – 6/120
6/120 – 6/60
6/60
Restricted visual fields with acuity > 6/60
Unknown
5.2
9.1
1.2
15.7
9.9
18.2
27.7
5.7
7.3
Functionally Blind
These form a relatively small proportion of the blind population.
- unable to read of write visually- unable to move or orientate visually- unable to recognise objects visually
SENSORY SUBSTITUTION e.g. Braille
Many legally blind people have some residual visual function
VISUAL ENHANCEMENT e.g. LVAs
Service delivery model
The Multi-disciplinary Approach to Low-vision Care.
The consequences of visual impairment may affect many aspects of a Px’s life.
Any low vision treatment must include a comprehensive look at all the individual’s needs (vocational, educational, social, psychological,financial, optometric, medical …..).
OphthalmologistOptometristSocial workersOccupational TherapistRehabilitation worker
