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Chapter 10

Visual Impairment

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Visual Impairment

A. Definition and Background

Visual impairment ( VI ) refers to significant decrease in visual function that is due todisease, disorder, or loss of any of the structures of the visual system. VI is often dueto a loss of visual acuity, i.e. the eye is not able to see things clearly. VI can also bedue to a loss of visual field – the total area scan and cover by both eyes.

The World Health Organization (WHO) in 1992 has defined the following definition(always with reference to the better of the two eyes) in the 10th Edition ofInternational Statistical Classification of Diseases and Related Health Problems (ICD-10):

1. Low vision ( category 1) : Snellen acuity no better than 6/18m (corrected)

2. Low vision ( category 2) : Snellen acuity no better than 6/60m (corrected) or

visual field no better than 20 degrees

3. Blindness ( category 3) : Snellen acuity no better than 3/60m (corrected) or

visual field no better than 10 degrees

4. Blindness ( category 4) : Snellen acuity no better than 1/60m (corrected)

5. Total blindness ( category 5 ): no light perception

According to the 10th Edition of International Statistical Classification of Diseases and

Related Health Problems (ICD-10), low vision is defined as the best corrected VA

was between 6/18 to 6/60. Blindness is defined as the best corrected VA was less than

3/60.

For children with low vision or “partial sighted” (category 1 to 2), one has significantVI but still can use the residual vision to facilitate learning.

For children with blindness (category 3 to 5), they usually need special education bymethods not involving sight, e.g. to learn Braille.

In Hong Kong, child with moderate low vision (i.e. best corrected visual acuity equal

or less than 6/60) could study in Special School for the children with VI.

Child with normal visual acuity can also be classified into low vision or blindness if

the visual field has significant defect. According to ICD-10, if visual field is less or

equal to 10 degree, it could be classified as blindness. If visual field is less or equal to

20 degree, it could be classified as low vision.

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Table 1. Classification for visual impairment

Snellen Equivalent

(Best Corrected VA)

6/6 6/18 6/60 3/60 1/60 Light

perception

WHO (1980) standard Normal Visual

impairment

Severe visual

impairment

Moderate

blindness

Near total

blindness

Total blindness

ICD-10 Category Normal Low Vision (LV) Low Vision (LV)Visual Filed ≤ 20 º

degrees around the

central fixation

BlindnessVisual Field ≤ 10º around the central fixation

Special Education

Hong Kong

Normal Moderate LV Severe LV Totally Blind

School for Blind

Disability allowance Worse than 3/60 in the better eye

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B. Etiology

Prenatal onset Perinatal onset Postnatal onset

Developmental brainabnormalities

Congenital infection Genetic syndromes

Hypoxic ischaemicencephalopathy

Retinopathy ofprematurity

Infections Metabolic disorders

Genetic syndromes(e.g. tuberoussclerosis)

Trauma Infection Tumour Haemorrhage

Structures Examples

Eye :

Cornea

Lens

Aqueous chambers

Uveal tract

Retina/ macula

Optic nerve

Corneal clouding (infection or metabolic disorders)

Cataracts ( congenital, infection, metabolic disorders)

Glaucoma

Iris abnormalities ( e.g. Coloboma of iris in CHARGE

association)

Retinopathy of prematurity

Retinoblastoma

Retinitis pigmentosa

Chorioretinitis (e .g. Congenital infection like

toxoplasmosis)

Albinism ( with fovea hypoplasia, defective fundal

pigmentation, refractive errors )

Visual tract and cortex:

Optic nerve

Optic chiasm

Optic tract

Lateral geniculate nucleus

Optic radiation

Visual cortex in Occipital

lobe

Optic nerve ( e.g. neuritis, atrophy, glioma)

Brain lesion due to :

Trauma

Intracranial bleeding

Tumour

Hypoxic ischaemic encephalopathy

Developmental brain abnormalities ( e.g.

schizencephaly)

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C. Clinical course

Infancy

In general, infants with blindness or partial sighted have significant delay in the

development of gross motor performance, in prehension skills, and in the

development of attachment behavior.

The greatest delay occur in mobility related and locomotion related behavior

including precrawling, sitting, pulling to standing and walking. Prehension of objects

by the hands is also delayed in the infant with blindness.

Development of attachment

The infant with blindness shows a delay pattern. Smiling develops as a response to a

familiar voice occurs only inconsistently, even in 12 months old infants with

blindness ( 6 months delay compared to sighted children) . Exploration of the

caregiver’s face and smiling in response to familiar tactile-kinesthetic handling occur

around 6 months, the same time as dose smiling at a caregiver’s face in the sighted

child. Anxiety toward strangers appears at 1 year of age in the child with blindness,

but a reaction to separation is not apparent until 11 to 20 months of age ( a 6 months

delay compared to sighted children) . These delays are no doubt related to the inability

of the blind infant and caregiver to “communicate” by visual face to face contact. The

typical infant with blindness may make his or her needs for attachment and

comforting known through a sign system of hand gestures, which include “tactile

seeking”. These gestures, if unknown by caregiver, may be misconstrued as a sign of

disinterest.

Development of language: The infant with blindness, shows a delay in language

performance

Childhood

Children with visual impairment appear to have somewhat better auditory attention.

Few intelligence quotient (IQ) tests are available with normative data relating to

individuals with blindness. Hence comparing blind and sighted persons on the basis of

IQ is very difficult and probably inappropriate.

The most significant deficits in cognition and perception in children with blindness

occur in tasks that are aided by vision or visual experience. The best studied example

of this phenomenon is the development of conservation (Conservation refers to a

cognitive concept: a physical property remains invariant even though its perceptible

shape or appearance is transformed)

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By the age of 10 to 12, the child with visual impairment shows functional haptic

exploration search ability that appears to be more active and more efficient than

sighted children’s efforts at isolating features and discriminating different shapes. The

proficient blind haptic explorer also tends to remember what was felt more accurately

than the sighted child.

D. Diagnostic Assessment

1. Assessment for visual acuity ( Please refer to below optometrist visual

assessment protocol)

2. Assessment for the underlying cause of the visual impairment through detail

history taking, neurological examination and detail eye examination by

ophthalmologist.

3. Check for specific symptoms and signs:

Ocular signs and behavior in children with peripheral ocular impairment:

- Strabismus or squint ( loss of vision will cause an eye to drift)

- Nystagmus ( pendular or rotator nystagmus suggests poor vision)

- Leukokoria ( white pupil indicates opacity at or behind the pupil that can

be the result of cataract, opacity of the vitreous, or retinal disease e.g. ROP

and retinoblastoma)

- Corneal clouding or opacity

- Microphthalmia

- Poor eye contact

- Eye poking or pressing ( commonly seen in children with retinal disorder)

- Hold object close to eyes

Behaviour in children with cortical VI:

- Retention of residual vision

- Objects are brought close to the eyes to reduce crowding effect

- Tends to use peripheral vision and have a characteristic head turn when

looking at or reaching for an object

- Compulsive ligh gazing

- Attracted to bright colours such as red and yellow

- Some has hypersensitivity to light

4. Developmental Assessment

- Specific Developmental Assessment ( e.g. Reynell Zinkin scale) with norm

for blind children or partial sighted children

- Haptic exploration skills – child’s ability to use hands to explore a shape,

perssing down or squeezing it.

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E. Recommendation and Management:

1. Rehabilitation Service Referral

a. For children < 6 yr old –

i. Ebenezer Early Education Intervention Centre

ii. Ebenezer Child Care Centre

iii. Integrated Child Care Centre

iv. Special Child Care Centre

b. For children > 6 yr old –

i. Ebenezer New Hope School

ii. Ebenezer School

iii. Integrated Support Program under mainstream primary school

2. Referral to DK interim Intervention Program for Children with VI:

a. DK Physiotherapy

b. DK Occupational therapy

c. DK Optometry visual training

Aim of the program: --

Promotion of sensorimotor learning. As there is delay in early

sensorimotor development in the infant with VI as a result of a

deprivation of visual information, the introduction of paired auditory-

tactual cues to sustain the infant’s interest in and contact with the distal

world and encouragement of physical activity, promote the

sensorimotor learning.

Optimal use of residual functional vision

Encouragement of independence in mobility and self-care

Encouragement of independence in self-care and mobility Promotion of cognitive development

3. Recommendation of the use of corrective lens and optical aids by Optometrist

4. Referral to Ophthalmology team for consideration of surgical treatment for

specific eye problem (e.g. cataracts)

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Optometry

Cortical Visual Impairment (CVI)

Definition

Cortical Visual Impairment (CVI) is a temporary or permanent visual impairment caused by

the disturbance of the posterior visual pathways and/or the occipital lobes of the brain.

Cause of CVI

The most common causes of CVI include:

oxygen deficiency in the brain during or after birth; cerebral hemorrhage cardiac arrest encephalitis malformation of the brain during prenatal development; head injury; epilepsy; or

cerebral tumor.

Visual and Behavioral Characteristics of Children with CVI

Since cortical visual impairment is the results of damage to the brain, the nature of the

disruption of vision caused by this damage is related to the location and extent of the damage.

Certain unique characteristics behaviors were found.

Strong color preference: Red and yellow Only moving objects can elicit or sustain visual attention Visual latency- delayed responses in looking at objects Visual field preferences – as a result of visual field defect Difficulties with visual complexity – difficulty when an object itself presents a complex

display Light-gazing and non-purposeful gaze Difficulty with distant viewing Absent or atypical visual reflex- absent of defensive blinking Preference for viewing familiar objects Atypical patterns of visual-motor behavior- The ability to look at and touch an object at

the same time is not display. These two actions are performed separately.

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Visual Assessment:

Different assessment battery for different age group ( See below)

Visual assessment for infant and toddler

Visual assessment for pre-school age children

Visual assessment for school age children

Examination of Infants and Toddlers

a) Visual Acuity

Assessment of visual acuity for infants and toddlers include the following test.

1) Defensive Blinking2) Hundreds and Thousands’ Sweet Test3) Optokinetic Drum4) Keeler preferential looking test

b) Refraction

1) Non-cycloplegic retinocopy2) Cycloplegic retinocopy -Cyclopentolate hydrochloride is the cycloplegic agent of choice.

c) Binocular Vision and Ocular Motility

1) Cover Test2) Hirschberg Test3) Versions4) Near point of convergence

d) Ocular Health Assessment

An evaluation of ocular health could include

1) Ocular anterior segment and adexa2) Ocular posterior segment3) Papillary responses4) Visual field screening (confrontation)

Examination of Pre-school Children

a) Visual Acuity

Assessment of visual acuity for infants and toddlers include the following test.

1) Cardiff Acuity Test2) Lea symbols Chart3) HOTV test4) Sonksen-Silver Acuity System5) E Chart

b) Refraction

1) Static retinoscopy2) Cycloplegic retinocopy -Cyclopentolate hydrochloride is the cycloplegic agent of choice.

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c) Binocular Vision and Ocular Motility

1) Cover Test2) Hirschberg Test3) Stereopsis4) Versions5) Near point of convergence

d) Ocular Health Assessment

An evaluation of ocular health could include

1) Ocular anterior segment and adexa2) Ocular posterior segment3) Papillary responses4) Colour vision testing5) Visual field screening (confrontation)

Examination of school-age Children

a) Visual Acuity

Assessment of visual acuity for infants and toddlers include the following test.

1) Letter chart (e.g. Snellen Acuity Chart)2) Projector Chart

b) Refraction

1) Static retinoscopy2) Cycloplegic retinocopy -Cyclopentolate hydrochloride is the cycloplegic agent of choice.3) Subjective refraction

c) Binocular Vision and Ocular Motility

1) Cover Test2) Hirschberg Test3) Stereopsis4) Versions5) Near point of convergence6) Positive and negative fusional vergences (optional test)7) Accommodative amplitude and facility (optional test)

d) Ocular Health Assessment

An evaluation of ocular health could include

1) Ocular anterior segment and adexa2) Ocular posterior segment3) Papillary responses4) Colour vision testing5) Visual field screening (confrontation)6) IOP (optional)

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Recommendation and management:

1. Visual training

2. Recommendation the magnification aids or devices

Visual training for cortical visual impairment :

The goal of visual training is to maximize the use of functional residual vision

• In the initial stage of training, parents and professionals can work to getresponses from children who don’t seem to have any vision.

• Use strong visual stimuli (while being mindful of stimuli that could provokeseizures) and lots of contrast, such as a light source in a dark room.

• Use one object and combine several sensory stimuli in it. Go slow and givetime for responses.

• The second stage of training involves focusing, shift of gaze, tracking and thedevelopment of hands-on random grasping

• Stage three involves the integration of sensory and motor skills, toward anintentional grasp.

• Let the child to look then to touch to the stimulus.

Magnification devices for Distant & Near vision

1) Spectacle-mounted reading lenses2) Hand magnifiers3) Stand magnifiers4) Electronic devices

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Clinical Psychology

Intellectual Assessment for patients with Visual Impairment

Introduction

A visual impairment occurs when any part of the optical system is defective, diseased, or

malfunctions. It can also occur when the central nervous system is damaged, since the

brain not only governs and coordinates the optical system but also interprets (i.e.,

"processes") the visual stimuli sent to it by the eyes.

Although it appears to be true that the more sight a visually impaired child has, the more

likely he/she is to develop at a normal rate, there is little research to support a direct

comparison of blind children to sighted norms. In fact, current research suggests that

blind children may have their own set of norms (i.e., they may not follow all of the same

sequences, in the same order, at the same time, as sighted children). Therefore, what may

appear to be a "delay" for a blind child may, in fact, be normal for him/her. The most

noticeable delay in development for visually impaired children is in motor areas. Since

vision is a motivating sense, many of the motor milestones (e.g., head control, erect

posture, reach, locomotion) may fail to occur when expected. Early intervention has been

able to minimize these delays in many cases.

Assessment:

At DKCH, individual basic cognitive evaluation was carried out for children with

visual impairment.

Common Assessment tools

Reynell Zinkin (Medium of instruction: Chinese and English; aged 0-5)

Case management:

1. To feedback information to our medical doctors for overall case management.

2. To refer back to school for follow up and school-based support

3. Liaise with MSW for service application if applicable.

4. Individual follow up if necessary

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Occupational Therapy

Occupational therapy for children with Visual Impairment aiming at enhancing

child’s visual response, awareness towards the environment through multiple sensory

stimulations, facilitating use of hands in play, enhancing fine motor and visual-motor

integration skills.

Occupational Therapy Assessment

During the assessment, occupational therapist will:

1. Review records and all important information related to present medical illness,

birth history, developmental history, etc., from the assessment summary of the

medical officers and other allied health team members as well as the treatment records

before the initial intake;

2. Consult parents/caregivers to learn child’s visual response, habits and skills in

activities of daily living as well as to discuss with parents/caregivers about their

expectations and to assess their attitude towards the child’s problems in the initial

interview;

3. Conduct detailed assessment focus on neurological examination on muscle tone,

strength and primitive reflexes and reactions; orthopedic examination on active and

passive range of movement over limbs; seating posture; sensation; visual response on

involuntary visual patterns (reflexive) and voluntary eye movements (cognitively-

directed); fine motor skill and self-care activities include feeding, grooming, toileting,

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dressing and bathing. The assessment will be conducted through clinical observation

and non-standardized assessment tool, that is, Hong Kong Developmental Assessment

Checklist.

4. Observe child’s physical dependency and behavior, the level of assistance or aids

does child required, movement pattern as well as

parent-child relationship and interaction.

Occupational Therapy Intervention

In the management of children with visual impairment, different types of treatment

approaches such as Sensorimotor approach, Biomechanical approach, Neuro-

developmental approach and Rehabilitative approach will be used.

Treatment Planning:

Stages of visual training:

Stage 1: To elicit response to visual stimulation and stimulate

awareness of visual stimuli. Through present the stimuli in dark room,

vary the distance and intensity of stimuli, use one and then combine

several sensory stimuli as well as present the stimuli slowly and give

time for response;

Stage 2: To encourage consistent “fixation” and “visual tracking” in

horizontal, vertical and oblique directions as well as to develop hands-

on random grasping and active reach out;

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Stage 3: To facilitate integration of sensory and motor skills which

involves intentional grasp, eye-hand coordination and bilateral hands

coordination.

The training will be provided on individual basis by occupational therapist

focus training on postural control, vision, fine motor and self-care skills.

Besides, occupational therapist will also cooperate with optometrist to

deliver training emphasis on visual training.

Usually, toys are employed as the main treatment modality.

If necessary, fabrication of splints for position, home visit for environmental

adaptation and modification, prescription of assistive device to facilitate

child’s independence in performing the self-care activities and their parents/

caretakers in caring them.

Parent Education and Home Program:

Parent’s participation in training is much encouraged and appreciated.

Home program, environmental modification, handling techniques,

positioning and precautions are taught to parents/ caretakers, hence they can

practice at home.

Besides, special chair will be prescribed for child to use at home so as to

facilitate visual and hand function training as child being positioned with

proper sitting posture.

•

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Physiotherapy

Both motor activities and natural spontaneous interactions with environment are crucial for

motor development of young children. However, visual impaired children are not motivated

to explore their surrounding environment and have difficulty in developing spatial

orientation, balance, understanding of the world and locomotor skills etc. Physiotherapy for

visually impaired children aiming at developing visual response, facilitate motor skills

development and enhancing participation in different ADL.

Physiotherapy Assessment :

1 To assess the gross motor development and motor skills2 To assess handling skills of carer/parents3 To formulate rehabilitation goal and plan involved parents and other parties e.g. school

to provide optimal rehabilitation outcome

Assessment (1) involves the following processes like: information, observation,

administration, recording and interpretation.

A physiotherapy developmental assessment will perform as followings:

1 aged-appropriateness of gross and fine motor functions2 neurological status3 musculoskeletal status4 developmental postural and balance reactions5 sensorimotor responses and/ or perception6 motor skill ability and coordination

The neurodevelopmental assessment will be performed. Details of neurodevelopmental

assessment could refer to the chapter of Motor delay. The assessment specific for visually

impaired children are highlighted as followings:

A. Gross Motor skills (basic)

a. Truncal stability

-Truncal stability especially in different position especially in prone as child with visual

problems may show more resistant to prone position which leads to delays in motor activities.

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b. Weight shifting and balance in different movement

-Segmental movement in spine

-Ability to maintain balance in different position

-Dynamic balance in different movement which may show delay development in visually

impaired children. They protect themselves by not moving around when the environment is

unknown.

-For children with cortical visual impairment (CVI), also need to assess motor performance

under controlled and uncontrolled environment.

Baby with blindness may resist to put into prone position

Uncontrolled environment:

e.g. present an object in front

of a complex display

Controlled environment:

e.g. present an object in front of

a simplified background

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c. Gross motor skills and development

-Rolling, Crawling, Walking, Balancing, Throwing and catching etc.

-To assess the best environment, position and toys to elicit visual response and improve

environmental awareness and interaction with environment with optometrist

B. Body Awareness

Recognition, identification, differentiation of body parts, dimensions, positions, movements

and spatial awareness which are very limited develop in children lack of visual input.

C. Parental handling and understanding of child’s special needs

-Assessing the handling skill of carer/parents, e.g. overprotection of children may limit gross

motor development of the children.

- To promote child and carer bonding.

Assessment Tool/ outcome measure

Peabody Developmental Motor Scales (PDMS)

Reflective toys for cortical visual impairment

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Physiotherapy intervention and training

For those children refer for CVI program, there will be joint assessment with optometrist to

evaluate the child’s visual response at different controlled/uncontrolled environment and

under different motor activities/position, to guide the setting up of the training goal and plan

taking into consideration of the residual visual function.

The progress of the patient may includes the following:

-Develop light perception

-Develop visual response in controlled environment, e.g. to a reflective toy in a dark room

-Develop better visual tracking

-Develop better motor-visual integration

Goal of Physiotherapy

-To promote gross motor development

-To promote better development of righting, balance, spatial awareness performance

-To empower parents to develop proper handling skills to avoid overprotection

Training program

a. Neurodevelopmental physiotherapy training

-To optimize motor performance in controlled environment with chosen toys

according to the characteristic of cortical visual impairment

-To advice on home exercises and daily handling

b. Multidisciplinary CVI training

-To encourage visual response, e.g. firstly develop interest to light or reflective toys,

develop visual fixation and develop visual-motor control etc.

c. Patient will be discharged when rehabilitation services available in EETC/ SCCC/

Ebenezer services

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Diagnostic and Management Flowchart in DKCAC

Confirmed VI

Children with suspected visual impairment ( VI )

History, Physical examination

Neurodevelopmental Assessment

Visual assessment

Refer Ophthalmologist for further workup on the

underlying cause ( if patient is not currently

following up by Ophthalmologist ) and follow-up

For children < 6 yr old:

1. Referral to DK interim VI intervention

program for visual training and

developmental training:

Optometrist/ Physiotherapist/ Occupational

therapist

2. Refer to DK Medical social worker for:

a. Local community resources

b. Early intervention service for

children with VI

For children > 6y old:

1. Referral to DK clinical psychologist for

intellectual assessment and

recommendation of school placement

2. Referral to DK Medical social worker :

a. Local community resources

Confirmed non-VI

e.g. ASD with poor

eye contact

e.g. severe MR with

poor visual follow

Follow relevant

protocols

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Patient referred to optometrist for

suspected visual problems Without visual problems

With visual problems

Refractive error

Amblyopia

Binocular visual

problems

Colour Blindness/

Deficiency

Cortical visual impairment

Spectacles Rx to

patient

Occlusion therapy with

active therapy

Visual training exercise

Consultation

Ocular disease:

Gluacoma, retinal degeneration, corneal problems, constant

strabismus etc.

Refer to DK Medical Scocial Worker.

Medical Social Worker will refer the case

to Ebenezer Early Intervention Program.

Before the child can receive the services

from Ebenezer Early Intervention

Program, CVI training program will be

provided by optometrist, physiotherapist

and occupational therapist in DKCH.

Discharge & reassurance

With visual

impairment

Refer to

ophthalmologist

Without visual impairment.

Case will be managed by the

optometrist

Pathway for Optometrist assessment for children with suspected visual problems

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Pathways for Occupational therapy Assessment of Children with Visual Impairment

History & Subjective Data

Personal information

Birth history

Medical history

Developmental history

Social background

Parent’s complaints and attitude

Objective Data

Visual response

Sensory response

Muscle strength and endurance

Active and passive range of motion

Postural tone

Seating posture

Abilities

Level of independency

Independent

Facilitation/assistancerequired

Dependent

Functional skills

Fine motor

Oral motor

Self-care / useof equipment

Behavior

Motor behavior

Postural alignment

Postural stability andmobility

Recommendation on TreatmentPlans

Training goals

Frequency of training

Parental education

Prescription of splinting, seating system (e.g. special chair), aids and equipment

On-going Evaluation / Re-assessment

Discharge

Static progress with home program

Continue OT service in other HA setting or special services (EETC / ICCC /SCCC / special school)

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Pathways for Occupational Treatment of Children with Visual Impairment (VI)

Treatment Areas

Postural Control

Normalize tone

Righting reaction

Protective extension

Equilibrium reaction

Sensoi-motor

Functions

Functional Training Parental Education Others

Self-care

Control

Fine Motor Vision Tactile Auditory Vestibular Kinesthetic Proprioceptive Visual-perceptual

Reaching Grasp & release Hand manipulation

(from unilateral to

bilateral)

Feeding Grooming Dressing Toiletting Bathing

Training andeducation onhome program,positioning andhandlingtechniques

Fabrication ofsplints

Home Visit forenvironmentaladaptation andmodification

Prescription ofspecial chair /wheelchair

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Pathways for Physiotherapy Assessment of Children with Visual Impairment

Assessment to be in details

Gross Motor Skills

Truncal stability Weight shifting Static Balance Dynamic Balance Segmental movement Motor skills e.g.crawling, walking etc

Body Awareness

Recognition ofbody parts Spatial

awareness Positional sense

etc.

Parental handling

Handling skills e.g.overprotection of children Child and care bonding

Joint CVI visual assessment with

optometrist

Neurodevelopmental physiotherapy

assessment for visual impairment

Subjective assessment

Personal Data Birth History Past and Present Medical

History Investigation Result Social History Educational level Parent/carer concern

Objective assessment

Gross Visual Response Gross response of hearing, speech and tactile response Musculoskeletal assessment Resting and Postural tone Gross motor skills Developmental assessment

Visual response

Visual response todifferent stimulus Need for environmental

modification Preferred colour Visual tracking Visual-motor

integration etc.

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Reading Materials:

Finuala M M and Mary O (1989). Observations on the Motor Development of Visually ImpairedChildren, interpretations from video recording. Physiotherapy 9, 505-508

Elspeth F, (2002). Physical Rehabilitation Outcome Measures second edition, CanadianPhysiotherapy Association, Canada (p192-193)

Christine R-L (2008). Cortical visual impairment, an approach to assessment and intervention.Ch 1, 2 and 3.

Boehme, R. (1998). Improving upper body control. An approach to assessment and treatment oftonal dysfunction. Therapy Skill Builders.

Case-Smith, J., et al. (2005). Occupational therapy for children. 5th ed., St. Louis: ElsevierMosby.

Han, J.E., & Groenveld, M. (1993). Visual behaviors and adaptations associated with corticaland ocular impairment in children. Journal of Visual Impairment and Blindness, 4:101-105.

Balliet, R., Blood, M., & Bach-y-Rita, R. (1985). Visual field rehabilitation in the corticallyblind? Journal of Neurology, Neurosurgery, and Psychiatry, 48:1113-1124.

Tsang L, Doo S. Visual Impairment. In : A primer in common developmental disabilities.

Experience at Child Assessment Service, Hong Kong. Child Assessment Service, Department of

Health, HKSAR 2006, pp 405

Larry W Desch. Visual and hearing impairment. In The Physicain’s guide to Caring for children

with disabilities and chronic conditions. Nickel RE, Desch LW. Ed 2000. pp265

Philip W Davidson, Christine M. Burns. Visual impairment and blindness. In; Developmental-

Behavioural Pediatrics 3rd ed . Levine MD, Carey WB, Crocker AC . pp 571