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Low Vision Assessment in children:

By:

Miss Ayesha Saleem

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Functionally, low vision is characterised byirreversible visual loss and a reduced ability toperform many daily activities, such as recognising

people in the street, reading blackboards, writingat the same speed , and playing with friends.

Many children with low vision can perform betterthan their parents or carers expect and have the

same quality of life as any other child, providedthat their treatment follows these steps, and inthis order:

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Examination to establish the cause of visual loss

Surgical interventions where appropriate (such as cataractsurgery)

Assessment of the child's various visual f unctions (distance

vision, near vision, contrast sensitivity, and visual field) Accurate refraction and provision of spectacles

Assessment for and prescription of low vision devices, suchas magnifiers

Suggestions for non-optical low vision devices such asreading stands

Educational support and training in the use of low visiondevices (with follow-up).

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Regular follow-up visits to clinical services are

very important, as the visual needs of children

can change rapidly (e.g. the size of the text

used in school books gets smaller as they

progress through school).

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Educational care for children with low visionincludes training children directly in the effectiveuse of their best vision. This can involve their

learning to write at closer distance, to usemagnifying devices, or to use creative strategiesto determine what is written on a blackboard(such as asking a child seated nearby to read

aloud while the teacher writes). This training isimportant, as it enables children to attend localschools.

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Visual Responsibilities:

1-3 months

attends to light and forms

follows moving objects and lights stares at faces

eyes fixate, converge and focus,

discriminates faces

swipes at or reaches towards an object

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3-7 months

eye movements smoother, acuity improving

manipulates and looks at objects

attempts to reach for objects recognises familiar faces and objects

tracks objects across entire field of vision

shifts visual attention from object to object

reaches and rescues dropped objects

fluid eye movements

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7-12 months

manipulates objects

watches movements and scribbling visual acuity and accommodation good

looks for hidden objects

imitates facial expressions and gross bodymovements

plays looking games

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1-2 years

all optical skills refined

fits objects together

matches objects

points to objects in book

imitates strokes and actions

scribbles or marks with a pen or brush

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2-4 years

visually inspects objects in distance

imitates movements of others

matches colours orders objects by colour

matches geometric forms

draws crude circle

puts two puzzle pieces together

matches identical shaped objects by size

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4-7 years

discriminates, identifies and reproduces abstract figuresand symbols

traces, copies and draws figures

identifies and perceives relationships in pictures, abstractfigures and symbols

identifies missing detail in pictures

identifies perceives and reproduces symbols singly and incombination (letters and words)

identifies letters in different print styles

reproduces abstract symbols from memory

identifies words on sight

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Visual skills:

Visual skills are ordered in 7 steps. An assessment shouldinclude activities that follow the order laid describedin areas of visual skills

Factors to consider when choosing objects for assessment:

size contrast

familiarity

distance

colou

r lighting

simplicity and detail

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Steps:

1. Awareness and attention to objects

Finding an object or target and looking at it (fixating) long enoughto be aware of it or recognise it.

Reason for assessment: Can a person see objects close to them?

Does the person search for objects visually or with their hands?What makes objects easier or possible to be seen?

Factors that affect how easy an object is to find or recognise are:

size

distance

contrast familiarity (makes it easier to recognise)

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2. Control of eye movements - tracking

Being able to follow moving objects with the eyes or headmovement.

Reason for assessment: Can the person follow themovement of objects without "losing" where they havegone?

Different directions of movements should be tested:

up and down

side to side

diagonal and

near to far

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3. Control of eye movements - scanning

Accurately moving eyes from one object to another.

Reason for assessment: Some people with low visionhave to search around for a long time to find objects.Some may find it difficult to change from looking atnear objects to look for something f urther away.

Searching the visu

al environment to look for a personor object requires scanning skills. An example is lookingfor a stall in a market.

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4. Discrimination of objects

Recognition of objects from an outline or general shape.

Reason for assessment: To learn if a person can

discriminate between people and objects, recognisefamiliar objects, recognise different or similar objects.

Objects can be discriminated because of their colour,shape, contrast, position or size- for example differentfoods in a market. The details within objects do not have to

be seen.

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5. Discrimination of details to identify actions and match objects

The discrimination of detail to identify an object is more difficultthan seeing the object. Features of the object have to be identified.

Reason for assessment: Most learning occurs from visual awarenessand imitation. It is important to know what can be seen and howthe environment (such as lighting) affects. The factors of distance,size, colour and contrast are very important.

Matching objects. Objects may need to be discriminated or

matched by size or shape.For example - get the largest stick or finda stick the same size.

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6. Discrimination of details in picture

Gaining information from pictures. Pictures can be simpleoutlines or complex, detailed pictures. The important

features (parts) in pictures have to be identified so that themeaning of the picture can be understood.

Reason for assessment: Pictures give usef ul information onposters, advertisements or in books. Objects in pictures

may be difficult to find and recognise.

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7. Identification and perception of patterns, numbers and words

Matching letters and numbers by the similar or different features of them. This does not require reading but is a necessary skill forreading.

Reason for assessment: To find out if a person can discriminatebetween similar and different shapes and letters. The results willhelp in making decisions on whether a person should use normalsize print, large print, low vision devices or may need Braille.

Discrimination is more difficult when the shapes are similar.

Recognition of words and matching them with pict

ures.

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Near Visual Acuity:

For fluent reading, an acuity reserve of 2:1 is

considered necessary. For example a child

needs to read a print size of N16 (2.0M) is

likely to need a threshold near acuity of 

atleast N8 (1.0M) to provide sufficient acuity

reserve to be comfortable in prolong reading.

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Steps to assess a reading add in

children:

Identify the print size child wants to read.

Measure childs near visual acuity at his or her

habitu

al working distance. Calculate the expected accommodation for

age: Amplitude = 15 (0.25 X age)

Calcu

late the estimated add. Estimated add: working distance in diopters

½ amplitude

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Cont.

Re measure near VA with estimated add, and

note threshold, fluency of reading, any

changes in working distance, and with older

children subjective preference.

If child is reading with this add easily then

prescribe.

If child is not reading print size easily then

increase the add.