Assessment Of Binocular Vision In Children Flashcards
How can we tell if a patient has BV or not
- aligned visual axis
- corneal reflections
- cover test
Normal Level of vision in children (18-23mths),(24-29mths),(30-36mths)
18-23 - 6/24 to 6/7.5
24-29 - 6/15 to 6/7.5
30-36 - 6/12- 6/6
Challenges of testing infants
- Can’t speak - struggle to verbalise subjective prescription
- Can’t read - letter testing impossible
- lose concentration
- lose interest
How to be successful in testing children
- choose age appropriate test
- be engaging
- beware of behavioural cues
- use comfortable occlusion
What is a Qualitative assessment
- estimation of VA
- based on Px reactions
- comparing behaviour for both eyes
- assess fixation
- reaching for objects
What is a Quantitative assessment
- precise measure of VA
- requires Px to identify the minimal separable
- logMAR
- Cardiff acuity cards
- preferential looking
What is optokinetic nystagmus, and how is it tested
- a physiologic phenomenon produced by asking the patient to visually track a succession of moving stimuli
- OKN drum
- stripes move across field of vision
- Px focuses on one stripe, then a quick movement in the opposite direction
- drum is rotated vertically in front of infant and response is observed
How to assess fixation
- fixation to a light To assess corneal fixation
- held at 33cm
- torch can be moved around to see if it can be followed
- bright colourful toys
- using ophthalmoscope, with graticule looking for white reflex
Fixation preference in strabismus
- alternating squint -> equal or near equal vision
- Holds fixation briefly -> small difference in vision (2 lines)
- does not hold fixation -> slight difference in prescription (3 lines)
- slow to talk up fixation: likely very reduced
- slow to move, and only moves slightly -> non absolute eccentric vision
- doesn’t take up fixation at all
How to testVA in a baby
Forced choice preferential looking
FCPL principle
- infants prefer to look at patterned background, rather than a blank surface
- Keeler or teller cads
- 17 cards with black white stripes
- 1 blank card
- hole in the centre
- square wave gratings of different spatial frequencies
- spatial frequency = cycles/degree
- range of 0.18 - 38 c/degree
Who is suitable for FCPL
- 8 weeks to 6/12 months
- mental disability
FCPL method
- 38cm distance
- 2 correct responses means move to next level
- staircase method - up if correct, down if wrong
- stop when can make any more judgement
What are Cardiff Acuity cards
- grey cards with familiar pictures
- vanishing optotypes
- picture beyond acuity threshold = invisible to Px
- picture at top or bottom
- 3 cards for each acuity level
Who is suitable for Cardiff acuity cards
- 6/12 months to 2 years
- children & adults with mental disability
Cardiff cards method
- held at 50cm or 1m
- present cards at eye level
- begin with most obvious target
- observe eye movement
- 2 out of 3 correct response to move up
How to test VA in a toddler
Kays picture test
- single logMAR
- crowded logMAR
What is Kay’s pictures
- well known pictures in a flip book
- pages with smaller acuities have 2 lines per page
- available in 2 formats
- comes with matching card
What is single logMAR Kays pictures
- based on same principle as logMAR acuity testing
- 3m testing distance
- 1 picture per page
What is crowded logMAR Kay’s pictures
- 5 pictures in a line of reducing size
- linear crowded test
- same principle as acuity tests
Suitability for Kay’s picture
- 2/3 years
Kays pictures method - single
- occlude 1 eye
- 3m testing distance
- choice of 3/4 pictures per acuity level
- VA range from 1.00-0.00 logMAR
Method - crowded Kay’s pictures
- Occlude 1 eye
- matching card
- 3m testing distance
- 5 pictures in a line with crowding box
- count number of pictures seen on smallest line
- correctly identified each picture on new book counts as 0.02
- VA range from 1.00-0.100 logMAR
How to test Pre-school children
LogMAR crowded acuity test
- 2x crowded books
- 4 letters at each acuity level inside box
- 1x uncrowned book
- 2 letters at each acuity level
Suitability of crowded logMAR
Preschool
Crowded logMAR method
- 3m
- practice with matching cards first
- record the same os logMAR
- 0.100 in crowded logMAR = 0.200 in ky pictures
What is sonsken
- based on ETDRS
- similar to crowded logMAR
- 2 flip books
- 4 letters within crowding bar
- matching card
- 3m testing distance
- near vision card
How to tell if there’s reduced vision in a baby
- how do the parents think the baby sees
- does the baby make eye contact
- does the baby respond or copy facial expressions
- does the baby notice if the lights are switch on/off
- do the babies pupils react
