7.1.4 Understands techniques of assessment of infants

Question 1

What are the normal vision levels by age?

Answer 1

• Birth: 6/300
• 1 mth: 6/200- 6/90
• 3mths: 6/90-6/60
• 6mths: 6/90-6/60
• 9mths: 6/36-6/30
• 1yr: 6/18
• 18mths: 6/12
• 2yrs: 6/12-6/9
• 3-4yrs: 6/9-6/6
• 5-6yrs+: 6/6-6/5

Question 2

What are the average Rxs by age?

Answer 2

• 1-3mths: +3.00
• 6mths: +2.50
• 12 mths: +2.00
• 18 mths: +1.50
• 2 yrs: +1.25
• 3 yrs: +1.00
• 4-6 yrs: +0.50

Question 3

What is resolution? What is recognition?

Answer 3

Resolution (minimum resolvable) – smallest angular separation between adjacent targets that can be resolved(spatial frequency grating). Limited by optical limitation of the eye and retinal photoreceptors spacing.
Preferential Looking and VEPs: can estimate acuity in infants.
Recognition (minimum recognisable) – type of acuity measured with Snellen chart.
Ability to identify a form (letter/picture matching/recognition) or its orientation.
Used from 2.5yrs.
More sensitive to pathological and physiological degradation.

Question 4

What is optokinetic nystagmus?

Answer 4

– Combination of a saccade and smooth pursuit eye
movement which develops around 6 months.
Crude assessment to show that the visual system is intact.
Using an optokinetic drum, spin it in front of the Px and watch their eye movements
- Rotated vertically in front of px
- OKN drum has black and white stripes on it

Question 5

Describe preferential looking (FCPL)?

Answer 5

way of estimating VA in infants and non-verbal Px.
Child is shown two circles. Principle is that the child will look towards the patterned circle
instead of the blank stimulus.
Pattern is a square wave grating (alternate black and white lines of equal thickness).
* Present the grating and record the looking response
* highest SF that gives correct looking response used to estimate VA.
- Keeler or Teller Acuity cards
- narrower strip: higher no., higher spatial freq, closer stripes together, higher VA (harder to see)
- 38cm testing distance
- 2 correct responses means you can move to next

Question 6

Describe cardiff acuity cards?

Answer 6

An image with a white band bordered by two black bands on neutral grey background is
shown.
Preferential looking’s only method of assessing VA
- VA range: 6/60 - 6/6 at 1m, 6/120-6/12 at 1/2m
- Card held at 50cm or 1m
- 2 out of 3 correct responses
- Watch for eye movements

Question 7

Describe Kay’s Pictures, Lea Symbols, Landolt C and tumbling E, Sheridan gardner and logMAR acuity cards?

Answer 7

Kay Picture Test
* For young children who are unfamiliar with letters (age 2 – 3),
* Consists of shapes which are considered easily recognisable to age group,
* 6m testing distance (no mirror)
Versions:
* Snellen notation
* Crowded
* Uncrowded
Lea symbols
* Four different shapes, when child can no longer resolve picture it blurs into a
circle, 2-3 years
Tumbling E and Landolt C
* uses Snellen E or C in different orientation,
* Px must identify correct orientation,
* Repetitive test, children 3 or over
Sheridan-Gardiner
* Key card with selection of letters used, no crowding, Snellen letters (2.5-3yrs)
LogMAR Acuity Cards
* Four letters within a box
* Scored by letter (0.025)
* 3m test distance.
* Crowded (3.5-4yrs) and Uncrowded version (2.5 -3yrs)

Question 8

Describe near vision testing in children?

Answer 8

• Large AoA so children tend to have few near vision problems
• Kay pictures and Sheridan-Gardiners near charts (2.5-3yrs)
• Tumbling E on budgie stick

Question 9

Describe Hirschberg test?

Answer 9

• Often the only test of binocularity in young children
• Quick and easy to perform
• Only performed at near
• Poor stimulus of accommodation
• Relatively inaccurate
• Reflexes central and symmetrical 0.5mm nasally (1mm = 20 prism dioptres)

Question 10

Describe cover test, motility and 20^ test?

Answer 10

Cover Test
* Use interesting detailed targets. The appropriate size target is important for
children with an accommodation disorder.
Motility
* Ideally use a light, if not then a toy of some kind
* Get the parent to hold child’s head.
20 Prism Dioptre Test
* (10-20 Base Out)
* Binocular recovery to base out prism

Question 11

Describe Lang test, Frisby, TNO and Titmus fly?

Answer 11

Lang Test
* stereograms become invisible when presented vertically
* 1200 -200 secs
Frisby Test
* uses real depth cues, with minor modification can be used to test infants as early
as 7 months
TNO
* Random dot stereogram
* Red/green glasses
* most challenging
Titmus Fly
* Polarising glasses
* monocular clues
fly easy 3000 secs of arc.