Finding out about functional vision AAC SIG: Making Sense of AAC November 4th 2014.

Finding out about functional vision

AAC SIG: Making Sense of AAC

November 4th 2014

Judy Bell

Independent consultant in visual impairment & complex needs

[email protected]

What the session will cover

Brief considerations of:• The nature of functional vision• The differences between functional &

clinical vision assessment • Who might carry out functional vision

assessment• The aspects of functional vision that will

impact on the choice and use of AAC• How these aspects might be assessed

The nature of functional vision

Functional Vision

Functional vision is the way an individual uses his or her sight in everyday situations

Functional Vision

An individual’s level of functional vision will vary according to both internal (e.g. health, hunger, tiredness etc.) and external conditions (e.g. location, lighting etc.)

Functional and clinical vision assessment

Functional vision assessment

• Assessment is via observation of structured activities and interaction in everyday situations

• Assessment takes place in an environment which is familiar to the individual

Clinical assessment of vision

• Direct clinical examinations are undertaken

• Standardised test material is used

• Assessment is usually within a clinical setting such as an optometrist’s examining room or hospital clinic

Individuals involved in functional vision assessment

• Often co-ordinated by a QTVI or QTMSI although anyone who knows and works with the individual can undertake such an assessment

• The observations of those who know the child well contribute to the assessment

Practitioners who may be involved in clinical vision assessment

• Ophthalmologist (eye doctor)• Optometrist (ophthalmic optician)• Orthoptist (specialist in binocular vision & eye

movements)• Paediatrician• School nurse

Usually these practitioners are not familiar to the individual

Aspects covered by clinical vision assessment

• Appearance & health of eyes• Refraction• Eye movements• Alignment of gaze & binocular vision • Visual acuity (distance)• Visual acuity (near)• Visual field• Contrast sensitivity• Colour vision

Aspects covered by clinical vision assessment

Visual acuity (distance)

Visual acuity distance: Snellen

• Fraction-like figure, e.g. 6/6, 6/12, 6/18, 6/24, 6/36, 6/60

• Bottom figure refers to the distance at which an individual with normal sight would be able to perceive image clearly

• Top figure refers to distance at which the person being tested is able to perceive the image clearly

Visual acuity distance: logMAR

Using the logMAR system, visual acuity is recorded as a decimal figure 0.0 to 1.0.

1.0 equates to Snellen 6/60

0.6 equates to Snellen 6/24

0.1 equates to Snellen 6/7.7

0.0 equates to Snellen 6/6

Clinical vision: Assessment to threshold

• Clinical vision assessment tests to the threshold at which an individual is able to see clearly

• No individual will willingly perform to visual threshold 100% of the time

Functional vision: Assessment of typical use of vision

• Functional assessment identifies how an individual uses his or sight in identified situations

• Functional vision assessment provides a picture of an individual’s ‘typical’ use of vision in everyday situations

Clinical and Functional Assessment

• Functional assessment should be ongoing

• Clinical assessment needs to be undertaken on a regular basis

Clinical and Functional Assessment

• Together, the clinical and functional assessment of vision provide a full picture of the visual needs of an individual

• Both will be required in order to determine the nature of AAC to be used.

Aspects of functional vision that will impact on the choice and use of AAC

AAC: Aspects of functional vision

Initial considerations:

• Willingness/reluctance to use vision

• Preferred sensory channel(s) – single or multi-channel

• Variability of vision

AAC: Aspects of functional vision

• Near vision will be main, but not only, concern

• If signing is used, an assessment of distance vision will be important in order to establish optimal distances

• Difficulties with distance vision will affect incidental learning & subjects available for communication

AAC: Aspects of functional vision

Near vision – consider preferred

• Lighting: – Strength – Type (natural, colour, LED, overhead,

backlighting, task etc.)

AAC: Aspects of functional vision

Near vision – consider preferred

• Size of stimulus (bigger not always better)

• Distance of stimulus (function of size)

• Position of stimulus (direction and plane)

AAC: Aspects of functional vision

Near vision – consider preferred

• Contrast

• Colour

• Tone

AAC: Aspects of functional vision

Colour, tone & contrast

Colours of a similar tone – poor contrast

Photocopy

Colour, tone & contrast

Colours with tonal contrast

Photocopy

Colour, tone & contrast

AAC: Aspects of functional vision

Near vision - consider

• Tracking skills: direction, speed, midline

• Scanning skills: direction, speed, midline, coverage

• Shift of attention from one stimulus to another: direction, speed, midline, coverage

AAC: Aspects of functional vision

Near vision - consider

• Visually directed reach and grasp– Locate, look & reach or….– Locate, look away & reach

AAC: Aspects of functional vision

Near vision - consider

• Clutter – stimulus & stimulus/background

• Visual distraction

AAC: Aspects of functional vision

• Clutter – stimulus & stimulus/background: Visual distraction

AAC: Aspects of functional vision

• Clutter – stimulus & stimulus/background: Visual distraction

AAC: Aspects of functional vision

• Clutter – stimulus & stimulus/background: Visual distraction

AAC: Aspects of functional vision

Near vision - consider

• Time taken for visual processing & response

AAC: Aspects of functional vision

Near vision – consider preferred• Movement of stimulus

– Constant – Intermittent– Still

• Sound production related to stimulus– Nature– Duration – intermittent or constant

• Nature of images– Photographs or drawings

How aspects of functional vision might be assessed

Functional vision assessment

• Observation in normal environment

• Observation of structured intervention and response

• Interview with those who know individual in different settings

Functional vision assessment

• Various schedules and profiles

• JB 2009 – Functional vision observations & assessment sheets – downloadable from website

Contact

Judy Bell

[email protected]

07748 657463

www.judybellassociates.com