Diagnosis of Cerebral Visual Impairment or Brain Related visual dysfunction
Diagnosing CVI requires little more than a curious clinician
Diagnosing visual problems in a child with suspected CVI requires a curious clinician, some simple adaptations to standard tests and an openminded approach to stepping out of our comfort zone to get into the comfort zone of the child.
Unlike other ophthalmological conditions, there is no neat set of standardised tests with a clear ‘normal/abnormal’ test range available to use. Rather the clinician must create a hypothesis of the nature of visual dysfunction the child has, based on listening to the parent’s concerns, observing them, or via an inventory. The clinician then chooses a test which may help them confirm or refute their suspicions.
The tests chosen will depend on the child’s attention, understanding and motor function. The aim is to build a picture of the child’s visual function starting with a blank sheet of paper, rather than assuming the child sees the way most children see.
Build a picture of the child’s visual function based on parent concerns, observed behaviours and simple tests
It may not be appropriate to assess areas of a child’s function at every visit: rather learning together the way the child uses their vision – HOW they see, not just WHAT they see – over a few encounters.
The aim is to learn together HOW the child sees, not just WHAT they see
The CVI Project published their testing protocol, used in children in mainstream primary school which is available here.
Ulster University published a review of all reported testing strategies, including inventories, in a paper here.
The Royal College of Ophthalmologists concise practice point will be available late in 2021.
What follows is a selection of the informal testing approaches which have been found to be useful as a starting point. Over time, each clinician will develop their own testing flow, finding tests they prefer for particular patient groups.
The overriding principle is to demonstrate areas of visual function, and highlight visual tasks which the child finds more challenging – this then will form the basis of a report alongside simple suggestions of how to Make It Easier for the child to see. While a formal diagnosis of cerebral visual impairment may be necessary for sight impairment registration or accessing services, the impact of a parent or teacher understanding HOW a child sees should not be underestimated.
General Function – WALK TALK READ FEED
Tell me about…
A good opening phrase is “Tell me about meal times? Tell me about how your child moves around? Tell me about what your child enjoys doing? Tell me about how your child communicates with you?
Walk– how does the child navigate? Do they bump into large objects on the floor? Do they find going DOWN steps and stairs tricky, are they disoriented in new places/busy shops? Can they find a toy they would like to play with? Can they use a scooter/bike?
Talk – how does the child communicate? Do they look away, turn their head? Do they look directly at people when speaking? Can they use PECS or a communication device? Do they recognise family members?
Read -what does the child enjoy doing? What TV shows will they watch? How to do they find apps/links on an iPad/phone? Can they choose what to play with? What sports do they play?
Feed – can the child feed themselves? Do they watch the spoon/bottle as it comes towards them? Do they look at the food on their plate? Do they reach accurately for it/a drink?
Testing strategy
The table below sets out a suggested testing approach and how the outcome might be described in a report for a parent, teacher or other health professional. The strategy should be adapted according to the child’s abilities, and undertaking flexibility in whatever order suits the child.
For children with the complex and multiple disabilities, where formal testing is not possible, documenting visual behaviours (ViBes) is important. The ViBe Matrix may be used to record what level of visual functioning the child has – awareness, attention, location, recognition – and which level they are working towards.
The ViBE Matrix – a structured approach to documenting atypical visual behaviours, to demonstrate verifiable visual dysfunction in children with CVI – click here
| Testing strategy (with links to less familiar tests) | Report may include.. |
| Visual acuity: LogMAR or Kays Check crowding ratio if VA <0.25 Near vision – is there a mismatch between N and D (relating to sphere of visual attention or accommodation) Cardiff Cards Bradford Visual Function Box (BVFB) noting distance, speed of response | What size objects the child easily sees What size text the child needs to see easily, what size icons should be on a communication device If text is more easily seen if spaced out or alone on a page |
| Visual Attention: Mirror test – how far away can the child hold their own gaze, what is their ‘sphere’ of visual attention (normal=2-3m, challenged 1-2m, impaired 0-1m) ( a video is here) How long does the child stay engaged for: how long do they need a break for before reengaging? Can the child locate a second object introduced into their visual field whilst they are looking something – use appropriate sized silent object (simultaneous perception) The BVFB can be useful for thiss Does the child deliberately look away/show visual avoidance? | The distance beyond which the child can’t ‘see’ anything- objects are lost amongst the background How long the child can use their vision for before needing a rest How long the rest should be, and to allow this in silence, avoiding addition sensory stimulation (eg encouraging by calling name, tapping.) To remove one task before introducing a new one. If the child finds visual tasks overwhelming and chooses to look away, allow this to happen. Simplify the stimulus and/or reduce background sensory stimulation. |
| Visual Field: Confrontation field with object size which matches acuity Note if there is inferior visual field inattention | Explaining whereabouts in the visual field the child finds it easiest to see Which side to sit to offer them food, which side to place a communication device, Which side should face into a classroom if in a wheelchair Whether to place objects/symbols side by side or vertically when offering the child a choice The need for objects to be raised up/shown above shoulder height/difficulty seeing objects on the floor |
| Ocularmotor function: use appropriate sized object (eg BVFB) Are pursuits smooth and undelayed Are saccades immediate and accurate Does the child reach accurately for an object? Do they maintain visual function while doing so? Does the child notice moving objects or do they need to be static? Does the child find static objects invisible and needs them to be moved before they are seen. | If the child cannot use visual search accurately, they may find it difficult to find a person, toy, book, track along a line of text efficiently If they cannot track a moving object they will not be able to see moving cars, balls children in a playground, characters on a fast moving TV show. If the child has difficulty coordinating vision and upper and/or lower limbs If the child will have problems seeing while they are walking/being moved about. IF they are able to see static objects or need them to be moved a little to bring them to visual attention. |
| Contrast sensitivity: Hiding Heidi | If the child finds low contrast (eg colour-on colour, pale on pale) objects difficult to see. |
| Accommodation: Dynamic retinoscopy- is there a change from ‘with’ to ‘against’ reflex when looking at a near object Is this sustained or delayed? | With impaired accommodation the child is unable to use ‘reading’( or feeding ) vision – everything close to is blurring or jumps around. They may need glasses to see things close to like an older person would eg to read a menu, see the food on their plate. |
| Visual Clutter: Identifying small toy from a cluster of toys on a plain background, then a patterned one(Also mirror test) Using Teddy Bear Cancellation test (here) to observe if child can identify teddy bears: if they are accurate and quick: if they have a random strategy (normal), can only identify those at the edges or methodical tracing approach (challenged). | Dysfunction may cause problems in locating shoes, clothes, crayons, toys. It may cause problems in finding the correct puzzle piece for a jigsaw, finding the correct name/word/letter in a matching game. Impaired function may be helped by offering objects one at a time, when being offered a choice; keeping objects in a standard location to reduce time needed to ‘search’. Offering a plain working surface with only one object or writing implement. Considering a ‘surround’ on the desk to to reduce distraction from clutter in the background. Finding text on a page with lots of writing/colour/images. They will find complex TV shows with busy backgrounds difficult and prefer simpler 2D ones eg Peppa pig. |
| Shape recognition/processing: Lea puzzle – do they select correct gap first time, or systematically move round each. Do they reorient the shape to be in the right configuration before it reaches the gap. Do they accurately pick up each shape. If successful, rotate the board by 90 degrees – do they reorient the shapes or use their memory to put them where the correct spot was on the initial test? Post box:Do they accurately orient the shape to fit through the gap when rotated into different angles | Dysfunction may cause difficulty with letter, number, shape learning. Children may not be able to recognise hand writing vs typed text: they may not be able to read unusual fonts. |
A sample record sheet is provided here and can be adapted to suit individual clinicians.
Some short videos demonstrating aspects of the testing are shown here
- Mirror test (from perspective of child
- Simultaneous perception/ inferior visual field attention (small BVFB, medium and large objects)
Make It Easier To See 