Developmental Journal for Babies and Children with a Visual Impairment
Presented on 1st May 2014
How Vision Develops in the Early Years
Janis Sugden, SSC Co-ordinator
Aims of this session
To look at the stages of visual development that typical children follow
To recap on what we mean by vision
To consider how vision is linked to other areas of development.
Are we born with our sensory gear fully functioning?
- In humans, the eye is only half its adult volume at birth (compared with 1/20 for the rest of the body)
- Distance from cornea to retina grows from 16 mm at birth to 24 mm in adulthood
- Rods and cones are present, functioning from birth
- The periphery functions much like it will in adulthood
- The central fovea is not well defined; cones are stubby and more sparse
- By one year, all the receptors are behaving like those of adults
- Optic nerve fibers become myelinated rapidly during first 4 months, reaching asymptote at two years
- Number of cortical cells in V1 is remarkably constant from 28 weeks from conception to age 70 years
Major principle: Sensory stimulation is mandatory for development to progress!
Typical visual development
Newborn 6/240
2-3 months 6/180 – 6/90
6 months 6/60 – 6/24
12 months 6/18 – 6/12
18 months 6/9
24 months 6/6 singles
4 years 6/6 test type
Vision
It is essential to make a distinction between eyesight and vision.
Eyesight = visual acuity which means how clearly we can see.
Vision = “guiding mechanism in the growth and development of learning … getting information in what you do with what you see” (Dr Joel N Zaba, Optometrist)
What do we mean by vision?
Vision differs from eyesight.
Eyesight is our ability to see.
Vision is a learned process.
Birth
- Corneal reflex to touch
- Pupil reaction to light
- Reflex closing of both eyelids to bright light shown in face. Lids will tighten during sleep.
- Saccadic system present at birth
- Cries real tears.
- Prefers human face to other forms of stimulus.
Vision: One to Two Weeks
- Rudimentary fixation on objects.
- May use only one eye at a time
- Fixates on facial expressions; may imitate
- Prefers contours, vertical and horizontal edges, larger sizes, simple patterns.
Vision: One to Three months
- Nystagmus induced by vestibular stimulation
- Stares at light source
- Follows moving objects, to midline first, then past midline
- Fascinated by bright lights and bright colours.
- Advancing fixation ability emerging convergence as close as 5 inches.
- Binocular coordination
- Begins to look within designs, instead of fixing on one spot along the perimeter.
- Hand regard, usually to side favoured by tonic reflex
- Swiping may occur on favoured side
- Vertical gaze movements emerging
- Shift eyes toward sound sources.
Vision: Three to Five Months
- Has stereo vision
- Fixates on objects at three feet
- Macular development at its peak
- Peripheral vision poor: field is only about one third of adult’s
- Advancing inspection of hands
- Central vision
- Emerging accommodation at distance of 5 to 20 inches
- Alternate gaze from hand to object and from object to object (rapid movement)
- Has colour vision
- Peripheral vision
- Has depth perception
- Preference for novel patterns begins to emerge.
Vision: Five to seven months
- Eye to hand coordination developed “top level reaching”
- Fixation fully developed
- Discrimination of forms
- Convergence occurs consistently
- Most binocular reflexes coordinated
- Responds differentially to facial expressions
- Begins to demonstrate visual memory.
Vision: Seven to eleven months
- Interest in tiny objects
- Tilts head to look up
- Smooth visual pursuit (follows with eyes and not necessarily head)
- Emerging depth perception
- Interest in shapes
- Visual pursuit is erratic: actually uses saccadic eye movements.
Vision: One Year
- Eyes and head move together
- Interest in shape sorters
- Tracking
- Interest in Pictures
Vision Twelve to Eighteen months
- Identifies likenesses and differences
- Interest in pictures
- Marks and scribbles
- Vertical orientation develops
- Demonstrates 20/20 acuity by 18 months
Vision: Two Years
- Scanning ,fixing, tracking.
- Language becomes important to help point out likeness and differences.
- Between 18 months and 3 years
- All accommodation develops
- Visual Image recalled
- Myelinization of anterior visual pathways complete by 24 months.
True creativity, understanding and efficient learning occurs when we use the Left and Right (halves) of the brain together.
Vision: Three Years
- Eye Movements and ball skills
- 4c’s compare, categorize, comprehend and communicate
- Between three to four years
- Copies geometric figures
- Eye hand coordination good
- Visualization is the key to learning!!!
- Visualization is the ability of the brain to remember the patterns of movement, the sequence of sounds and the feel of things.
Vision: Four Years
- Colour recognition; shadings, differentiations
- Sharpness and clarity of detail (fine movements)
- Depth perception fully developed ball skills, tracking
- Colour identification
- Visual spatial orientation developing
Paediatric Visual Impairment
3 main causes of visual impairment
- Problems of the eye
- The optic nerve
- The brain
When do sight problems occur?
Almost all sight problems occur before or at birth or on the first 28 days of life
It is estimated that 70% of visually impaired children have an additional disability (Ref VIS 2003)
What can go wrong?
Ocular
- Loss of visual acuity (The detail and clarity of what we see)
- Visual Field Loss (The area that we are able to see)
Cerebral or cortical visual impairment (CVI)
Vision in the first years of life
Dependent on intact eye, optic nerve and brain
Dependent on being stimulated
Problem with either then visual function will not develop normally
Effects on early development
Reduced vision may delay a child’s development in all areas.
- cognitive
- language
- fine and gross motor
- social and emotional
- self-help and independence
Acknowledgements:
Dr Andrew Blaikie Consultant ophthalmologist andrew.blaikie@nhs.net
Dr John Ravenscroft Depute Head Moray House School of Education john.ravenscroft@ed.ac.uk
Dr Karl Wall IOE London University K.Wall@ioe.ac.uk