Assessment of Vision in Infants & Children

Question 1

When are vision levels about normal from in children?

Answer 1

• Vision levels in children are initially poor at birth but rapidly increase over first few years of life
  o About normal from about 5 years of age
• Range of vision – not every child will see the same
  o Depends on many factors – e.g. not developing normally, ability to sit for tests

Question 2

What are the normal values for vision in children? 18-23 motnhs, 24-29 motnhs, 30-36 months?

Answer 2

18-23mths –> 0.6-0.1, 6/24-6/7.5
24-29mths –> 0.4-0.1, 6/15-6/7.5
30-36mths –> 0.3-0.1, 6/12-6/6

Question 3

Describe Qualitative Assessment in children?

Answer 3

• Useful in v young or uncooperative pxs
• Estimation of VA – objective
  o Can overestimate vision as they can see something but you don’t know what they’re seeing as they cannot tell you
• Based on pxs reactions
  o How does child react when you cover up a certain eye?
• Compare behaviour of the 2 eyes
• Records the minimal visible versus the minimal separable in quantitative testing
• Tests:
  o Assessment of fixation:
   Can give lots of info
   How well child can fix on something
   How well they can hold fixation – do they follow it around – are they happy to do that – do they do that up close and when far away
   Babies like lights so can use that – look for equal corneal reflections – are they looking with both eyes?
• Held at 33cm
• 5cm toy – brightly coloured – animal that they like – lights up and makes noise – Kay Pictures, Amazon, Tiger
   Also useful when child is old enough to do forced choice but uncooperative
• By 6weeks of age babies should be able to fix and follow – lights or faces etc
   Optokinetic Nystagmus (OKN) Drum:
• Easy to perform – another thing to try if running out of ideas
• Provides qualitative info – similar to fix & follow methods
• Stripes move across field of vision – create an eye movement
• Px fixates on one stripe & then a quick movement in opposite direction
• Drum is rotated vertically in front of infant & response is observed
• Child on parent knee
• Rotate drum – stripes moving vertically
• See if child interacts with stripes and follows them as they move
  o If child can see them they will follow them
  o Will get back and forth movement if child can see it & follow it
   Reaching out for objects – you know they can see it if they reach
   Hundreds & thousands - ~6/24 if they can pick it up

Question 4

Describe Quantitative Assessment in children?

Answer 4

• Precise measurement of VA
• Requires px to identify the minimal separable
• logMAR, Cardiff cards – gold standard eye test – to get accurate level of vision
• Tests:
  o Forced Choice Preferential Looking (GCPL) – youngest babies
  o Cardiff Acuity Cards
  o Kays Picture Test – useful in children who don’t quite know letters
  o logMAR
  o Sonsken
• Less Commonly Used Tests:
  o Lea Symbols, Sheridan-Gardiner Test, Landolt C, Tumbling E

Question 5

Describe assessment of fixation in children?

Answer 5

• Observing how well a child can fixate is crucial qualitative assessment
• Fixation to a light: assess corneal reflections
  o Held at 33cm
  o Can be moved around to see if child fixes & follows
  o Introduce small bright colourful toys – do they fix & follow
• Useful tool in pxs who are uncooperative for FCPL/ are suspect very reduced vision

Question 6

Describe fixed preference in strabismus? What does it mean for vision?

Answer 6

• Cover test results can give clues regarding vision
• Child will ALWAYS choose to fix with eye that is best seeing
• Alternating squint:
  o Equal or near equal vision between the 2 eyes
• Holds fixation briefly:
  o Small difference in vision between eyes – usually <2 lines
  o They can use the eye and happy to but not for very long – must not be very poor in that eye
• Does not hold fixation:
  o Likely significant difference in vision (> or equal to 3 lines)
  o Minute you tke away cover – no ability to use that eye – indicates that child has significant difference between eyes  vision not as good in this eye
• Slow to take up fixation:
  o Likely very reduced vision
  o Vision is reduced, using non-absolute eccentric fixation – not using fovea to look
• Slow to move & only moves out slightly:
  o Non absolute eccentric fixation
• Doesn’t take up fixation at all:
  o Eccentric fixation
  o Eye does not want to use fovea as vision so poor

Question 7

Describe testing a baby (0-18months)?

Answer 7

• These tests can be used in older children or equally 18month old may need an older child test
• FCPL:
  o Principle – infants prefer to look at patterned rather than a blank surface
  o Keeler or Teller Acuity Cards:
   17 cards w/ black & white stripes on right or left side
   1 blank card – to see if child has favourite side or decide between the two
   4mm hole in centre where examiner looks through
  o Square-wave gratings of different spatial frequency
   Spatial frequency = cycles/degree
  o The narrower the strip:
   Higher number
   Higher spatial frequency – closer stripes together (harder to see)
   Higher VA
  o Range of 0.18-38 c/deg  gives you a logMAR equivalent on back of each card
  o Suitability:
   8 weeks to 6-12 months (can try before 8 weeks if think it’ll work)
   Pxs with mental & physical disabilities – Cardiff Cards usually preferred method due to larger range
  o Method:
   38cm testing distance
   2 correct responses means you can move to next (they look at same side twice)
   “Staircase method” – presenting grating same number of times, moving up to next higher frequency & down if incorrect
   Stop when examiner can no longer make judgement on response
• Cardiff Acuity Cards:
  o Grey cards with familiar pictures
  o Vanishing optotypes
  o Picture beyond acuity threshold = invisible to px
  o Picture at top or bottom of card
  o 3 cards for each acuity level
  o VA Range:
   6/60-6/6 at 1m
   6/120-6/12 at ½m
  o Suitability:
   6/12 – 2year old
   Children & adults with disabilities
  o Method:
   Cards are held at 50cm or 1m
   Present cards at eye level – don’t look at card first – get child to look at picture first, see where they look then you look at the card to confirm if they got it right
   Begin with card with most obvious target (lowest acuity)
   Can be done at 50cm or 1m – younger the child the closer you’ll be to keep their attention
   Observe eye movements
   2 out of 3 correct response
   Can overestimate vision – know child is seeing something but don’t know what they can see – they may be able to differentiate contrast but don’t know if they can actually see a duck for e.g.
   Can be used in non-verbal children

Question 8

Describe testing a toddler/infant (18months-3years)?

Answer 8

• Kay Pictures Test:
  o Series of well-known pictures in a flip book
  o If child shy they may still want to match with you
  o Pages with smaller acuities have 2 lines per page
  o Available in two formats
  o Comes with matching card
  o Suitability:
   2-3 years
   Estimate:
• Single Kays 2-3years
• Crowded Kays >3 years
  o Kay Picture Single logMAR:
   Based on same principle as logMAR acuity test
   3m testing distance
   1 picture per page
   For each acuity level there are a few different pictures – don’t need to do every picture for every level
   Method:
• Occlude 1 eye
• 3m testing distance
• Choice of 3-4 pictures per acuity level
• VA range 1.00-0.00 logMAR
  o Kay Picture Crowded logMAR:
   Older – better ability to see and concentrate & speak
   More accurate than single
   5 pictures in a line of reducing size
   Linear, crowded test
   Same principle as logMAR acuity tests
   Method:
• Occlude 1 eye – use occlusive glasses not parent’s hand
• 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 0.020
• VA range 1.00 to -0.100 logMAR

Question 9

Describe testing pre-school (4-5years)?

Answer 9

• logMAR Crowded Acuity Test:
  o Glasgow Acuity test (Keeler) – 3m
  o 3 books & matching card
   2x crowded books
• 4 letters per acuity level inside crowding box
• 1 book for each eye so child doesn’t memorise letters
   1x uncrowded book
• 2 letters per acuity level
  o One line of letters is 0.1logMAR
  o Each letter worth 0.025 logMAR
  o Suitability:
   Preschool (3-5year olds) – most accurate and reliable for this age group
  o Method:
   Test at 3m
   Practice with matching card first
   Recording same as logMAR – smallest row of letters/no. of letters seen recorded

Question 10

What is an important rule about logMAR compared to Kay Picture?

Answer 10

0.100 in crowded logMAR = 0.200 in Kay Picture test

Question 11

Describe Sonsken test?

Answer 11

• Designed by University College of London
• Based on ETDRS
• Similar to crowded logMAR
• 2 flip books
• 4 letter with crowding bar
• Matching card
• 3m testing distance
• Overestimates vision – be careful when recording results
• Cheaper
• Near vision card

Question 12

What things should you consider if you suspect reduced vision?

Answer 12

• How parents think the baby sees
  o Parent usually knows if their baby is visually impaired – may respond to noise but not respond when someone walks into room
• Does the baby make eye contact?
  o Look at baby up close – will they look at you
• Does the baby respond or copy facial expressions?
  o Silent smile at px (don’t say anything or make noise) – and they smile back then likely they can see your smile
• Does the baby notice if the lights are switched on/off? – are they surprised, do they look around
• Do baby’s pupils react?
  o Should be light sensitive to bright light & squirm away – if they don’t do that then likely they cannot see it

Question 13

Describe the crowding effect?

Answer 13

• Better acuity is usually achieved in targets which are spread apart compared to targets that are closely spaced
• Normal & amblyopes
  o Amblyopes vision poorer when crowding rather than without crowding
• Characteristic of microtropia
• Crowding occurs when letters are 1 letter diameter apart with resolution maximally impaired when 0.4 letter diameter apart

Question 14

Describe testing near vision in a child?

Answer 14

• Testing distance 33cm
• Same rules apply about grading & logMAR – just doing it up close
• Typeset material:
  o Similar to newspaper print/book print – sentences, paragraphs, words
  o Not comparable to distance VA tests
  o N test types (Times New Roman)
  o Moorfields book
  o Maclure book
• Based on equivalent to distance chart:
  o Reduced Snellen
  o logMAR chart
  o Near single & crowded Kay picture (logMAR)
  o Single Sheridan Gardener

Question 15

Which test would you pick for each age group?
Birt-6mths? 1-2yrs? 2-3yrs? 3-4yrs? 4-8yrs? 8+yrs

Answer 15

Birth-6mths –> preferential looking
1-2yrs –> Cardiff Cards
2-3yrs –> Kay Pictures Single
3-4yrs –> Kay Pictures Crowded
4-8yrs –> Crowded logMAR
8+yrs –> logMAR chart

Question 16

What do you need to record when noting child’s vision test results?

Answer 16

• Which test was used – whether it was single or crowded (as next examiner may think vision should be better if you have not noted down correctly)
• The threshold level – encourage child to get to threshold & max level of vision you can – child will want to give up quickly when it gets hard as they don’t want to be wrong
• The testing distance
• Changes in behaviour between the eyes e.g. slower with RE
• If a compensatory head posture was used – if child has nystagmus they may use this to get null point (best vision)
• Note if glasses were worn or not