This document provides an introduction to low vision aids. It defines low vision as visual acuity worse than 6/18 but better than light perception in the better eye, even with proper spectacle correction. Low vision can be caused by visual field loss less than 10 degrees as well. The document discusses different categories of visual impairment including low vision, partial blindness, and subnormal vision. It also discusses common eye disorders that can cause low vision in children and adolescents such as Best's disease, cone dystrophy, and retinitis pigmentosa. Finally, it provides an overview of common low vision aids that can help those with low vision including magnifiers, closed circuit televisions, and distance low vision aids.

1. INTRODUCTION TO LOW
VISION AIDS
MS.PRIYADHARSHINI.M
LECTURER
DEPT OF OPTOMETRY
SCHOOL OF ALLIED HEALTH SCIENCES
VINAYAKA MISSION’S RESEARCH FOUNDATION-DU

2. WHAT IS LOW VISION?
 A person whose visual acuity is <6/18 to Perception of Light in the better eye
even after proper spectacle correction or Refraction is defined as Low vision
Patients
Or
 When a person’s Visual field loss is < 10◦ is termed as Low vision.
 When these defects affects a person’s regular tasks he/she can plan to use
special device or equipment to do the tasks.
 WHO: ICD-10

3. THE TERM BLIND
 The term blind differs as Educationally , Legally or Functionally and is often
used to indicate profound visual impairment.
 There are several blind associations for Blind

4. TERMINOLOGIES
 DISORDER
Usually used to describe the impact of the disease or injury on the anatomical structure
of visual function within the organ or, in the case of vision, a component of the visual
pathway
 IMPAIRMENT
The consequence, in terms of measurable loss or departure from functional capacity, to
the bodily organ, affected by disorder or disease, of an anatomical or physiological
function
 DISABILITY
The consequence to the patient in terms of the effect of the impairment on the patient’s
abilities
 HANDICAP
The consequence of the disability in terms of how it affects the patient’s ability to interact
with society

5. DEGREES OF VISUAL IMPAIRMENT
VISUAL IMPAIRMENT
PARTIALLY BLIND LOW VISION SUBNORMAL VISION
(between 6/24 and 6/60) (<6/18 to PL) (6/18 TO PL)

6. QUANTIFYING CATEGORY OF BLINDNESS
GROUP 1 DESCRIPTION
1 Visual acuity of less than 3/60 or less than
1/18 if tested at a closer distance, in a
patient with full visual fields
2 Visual acuities ranging from 3/60 to less
than 6/60 with significantly contracted
visual fields
3 Visual acuity of 6/60 or better with a gross
visual field constriction, particularly in the
lower field

7. QUANTIFYING CATEGORY OF PARTIALLY
SIGHT
GROUP 1 DESCRIPTION
1 Visual acuity of 3/60 to 6/60 with full fields
2 Visual acuity of up to 6/24 with a moderate
field constriction, medial opacities or
aphakia
3 Visual acuity of 6/18 or better with a gross
field defect (i.e. hemianopia)

8. CATEGORIES

9. LOW VISION
 Those approaching the problem of visual impairment from an optical or
optometric background advocate the term ‘low vision’, which to a large
extent has evolved from the term ‘subnormal vision’.
 This term is almost synonymous with visual impairment, with the added
provision that the residual vision is usable.

10. EPIDEMIOLOGY IN SOUTH INDIA
 Chennai is one of the four metropolitan cities in India and is popularly known as
the “health city” of India. In such an urban population, we found the prevalence
of blindness to be 0.85% (95% CI 0.6–1.1%), low vision 2.9% (95% CI 2.4–
3.4%), and visual impairment (blindness + low vision) 3.8% (95% CI 3.2–
4.4%)[1]
1.Prevalence and causes of low vision and blindness in an urban population: The Chennai Glaucoma Study

11. VISUAL IMPAIRMENT IN CHILDREN
 Visual loss in childhood and the early teens is predominantly congenital or
hereditary in nature.
 The three most common clinical scenarios presenting to the ophthalmologist
are
•The neonate or young baby who appears to be visually
impaired
• The visually impaired baby with no obvious ophthalmic
abnormality
• The child with visual difficulty.

12. CONTD….
 Eighty-three per cent of neonates will follow a face but not a white light. A smile
in response to a silent smile should be present at 6 weeks of age and indicates
good central vision.
 Abnormal eye movements and visual inattention are the most common signs of
poor vision. The more uncoordinated the movements, the more impaired the
visual acuity.

13. TEST DONE
 ELECTROPHYSIOLOGICAL TEST

14. The neonate or young baby who appears to be
visually impaired
• Albinism
• Cerebral blindness
• Congenital cataract
• Congenital glaucoma
• Congenital idiopathic nystagmus
• High refractive error
• Leber’s congenital amaurosis
• Macular colobomata
• Optic atrophy or hypoplasia
• Primary hyperplastic vitreous
• Retinoblastoma
• Retinopathy of prematurity.

15. History and examination
 Normally sighted in infancy.
 Normal early studies
 Starts with the poor vision while seeing blackboard
 In this age group a history of the visual symptoms and a positive family history
of inherited conditions may also be present.
 Children with decreased distance acuity with good near acuity may simply be
myopic.
 optic atrophy-complain of reducing vision but usually have no other specific
symptoms
 cone dystrophies – intense photophobia and difficulty with colour vision.

16.  early-onset retinitis pigmentosa - night blindness or restriction of fields

17. Classification of Loss or Impairment – Disorder and Impairment Relate
to the Organ whereas Disability and Handicap Relate to the Person
DISORDER IMPAIRMENT DISABILITY HANDICAP
Disease or injury Reduced functional
Performance
Reduced skills or abilities Limitations on social
performance participation
ARMD Reduced VA and CS Reading speed and fluency
reduced
Difficulty in accessing
written contents
RP Contracted VF, reduced CS
and impaired night
reduced Walking speed Mobility problems travel
and resulting social vision
CONGENITAL CATARACT Reduced VA & CS,glare,
and reduced near visual
acuity
Reading more difficult Difficulty in mobility and
isolate
OCULOCUTANEOUS
ALBINISM
Reduced VA &
CS,Photophobia
Mobility difficult in bright
light and DV problem
Restrictions to certain
travel tasks
THE ORGAN THE PERSON

18. Visual Prognosis, Visual Field Loss in
Inherited Diseases
CONDITION VISUAL
PROGNOSIS
VISUAL FIELD
DEFECT
VISUAL AIDS
LEBER’S
AMAUROSIS
VERY POOR COMPLETE LOSS
OF VF
REQUIRES SOME
SPECIAL
TECHNIQUES
OPTIC ATROPHY VARIABLE PARACENTRAL
SCOTOMAS
GOOD WITH LVA’S
CEREBRAL
BLINDNESS
POOR DIFFICULT TO TEST NEED
ENVIRONMENTAL
MODIFICATION
DELAYED VISUAL
DEVELOPMENT
NORMAL VISION
OFTEN DEVELOPS
NORMAL GOOD WITH LVA
AND TRAINING
WHEN GETS OLDER

19. Overview of the Functional Classification of Disability and
Health
FUNCTION &
STRUCTURE
ACTIVITIES AND
PARTICIPATION
ENVIRONMENTAL PERSONAL
DOMAINS Bodily functions Life areas (Tasks
and actions)
External influence Internal influences
CONSTRUCTS Anatomical and
Physiological
changes
Capacity and
performance
Hindrances of
features in
physical and social
world
Impact of
attributes on
person
POSITIVE
ASPECTS
Functional and
Structural
integrity
Activity
participation
Facilitators
functioning
NA
NEGATIVE
ASPECTS
Impairment and
Disability
Activity
limitation and
participation
restriction
Barriers and
Hindrances
NA
FUNCTIONING & DISABILTIES CONTEXTUAL FACTORS

20. Ophthalmic disorders presenting in
childhood
 Best’s disease or vitelliform dystrophy
 Cone dystrophy
 Optic atrophy
 Retinitis pigmentosa
 Stargardt’s disease or fundus flavimaculatus
 X-linked retinoschisis

21.  OPTIC ATROPHY:
The death of the retinal ganglion cell axons that comprise the optic nerve with the
resulting picture of a pale optic nerve on fundoscopy.
 Vitelliform dystrophy or Best’s disease :
Also known as vitelliform macular dystrophy, is an inherited retinal disease
causing macular degeneration.
 Stargardt’s disease or fundus flavimaculatus :
An inherited disease, meaning it is passed on to children from their parents. Stargardt
disease is a form of macular degeneration, and is often called juvenile macular
degeneration.

22.  Cone dystrophy :
An inherited ocular disorder characterized by the loss of cone cells, the
photoreceptors responsible for both central and color vision.
 X-linked retinoschisis :
A rare congenital disease of the retina caused by mutations in the RS1 gene, which
encodes retinoschisin, a protein involved in intercellular adhesion and likely retinal
cellular organization. X-linked retinoschisis has also been referred to as: juvenile
retinoschisis, congenital retinoschisis, juvenile macular degeneration/dystrophy,
and degenerative retinoschisis.

24.  Retinitis pigmentosa:
A genetic disorder of the eyes that causes loss of vision. Symptoms include trouble
seeing at night and decreased peripheral vision (side vision). As peripheral vision
worsens, people may experience "tunnel vision". Complete blindness is
uncommon.
 Usher’s syndrome :
Usher syndrome is a rare genetic disorder primarily characterized by deafness due
to an impaired ability of the inner ear and auditory nerves to transmit sensory
(sound) input to the brain (sensorineual hearing loss) accompanied by retinitis
pigmentosa, a disorder that affects the retina and causes progressive loss of
vision.

25. Disorders presenting in adolescence
 Best’s disease or vitelliform dystrophy
 Cone dystrophy
 Leber’s optic neuropathy
 Retinitis pigmentosa
 Stargardt’s disease or fundus flavimaculatus.

26.  Two rare but important systemic diseases are abetalipoproteinaemia (Bassen–
Kornzweig syndrome) and Refsum’s disease in young
 An inherited disorder that impairs the normal absorption of fats and certain
vitamins from the diet. Many of the signs and symptoms
of abetalipoproteinemia result from a severe shortage (deficiency) of fat-
soluble vitamins (vitamins A, E, and K)
 An inherited condition that causes vision loss, absence of the sense of smell
(anosmia), and a variety of other signs and symptoms. The vision loss
associated with Refsum disease is caused by an eye disorder called retinitis
pigmentosa.

27. USES OF LOW VISION AIDS
 Most children with mild to moderate visual impairment can cope in normal school,
given the following provisions:
• Good parental understanding of the problem
• Teaching and advisory peripatetic support
• A bright and dexterous child.
 Dome magnifiers are often the aid of choice for albinos and those with congenital
nystagmus.
 Aphakic children require higher levels of magnification and benefit from stand
magnification (×3 to ×12) or spectacle magnifiers (single vision or bifocal).
 Children with retinitis pigmentosa and central visual loss benefi t from closed
circuit televisions (CCTVs)
 Distance low vision aids can be used by virtually all schoolaged visually impaired
children

28. Non-pathological Changes in the Eye
with Age
 CORNEA - Corneal sensitivity to touch is decreased / Increase in ‘against the
rule’ astigmatism
 AC - Anterior chamber depth decreases with age
 IRIS - Senile miosis / Pigment desquamation into the anterior chamber
 LENS - Increase in axial thickness by about 28% / Increase in the amount of
yellow pigment leading to decreased sensitivity at the violet end of the
spectrum / Decrease in accommodation, possibly due to a decrease in
capsular elastic force / Little evidence to support atrophy or sclerosis of the
ciliary muscle

29.  VITREOUS – Chromatic aberration decreases with age / Index of refraction of
the vitreous increases / Liquefaction and syneresis occur
 RETINA - Visual acuity decreases as age increases / 75–85 years vision is less
than 6/7.5 [LogMAR 0.1] and they are entirely free from ocular disease Visual
field size decreases / Loss of ability to discriminate hues, especially at the
violet end of the spectrum / Mesopia and scotopia occur at lower levels of
ambient illumination / Absolute level of dark adaptation achieved is lower/
Delayed recovery to glare Loss of contract sensitivity at low frequencies /
Decrease in retinal illuminance / Decline in acuity with target velocity with
increasing age / Variability in visual performance increases with age

30. REFERENCE
 A.Jonathan Jackson,James S Wolffsohn, Low vision Manual , ISBN-13: 978-
07506-1815-1 ISBN-10: 0-7506-1815-9

31. THANK YOU