There are several tests that may be used to check your child's hearing and vision.
Hearing tests
Newborn babies are usually screened for any potential hearing problems using two quick and painless tests. They are the:
- automated otoacoustic emissions test (AOE)
- automated auditory brainstem response test (AABR)
These are outlined below.
AOE test
An AOE test only takes a few minutes and can be carried out while your baby is asleep. A tiny earpiece will be placed in your baby's ear and quiet clicking sounds will be played through it.
If your baby's ear is working normally, reaction sounds (echoes) should be produced in a part of the ear known as the cochlea. A computer is used to record and analyse the reaction sounds.
Sometimes, the results from an AOE test are not clear. In such cases, the test may be carried out again, or an AABR test can be used.
It's common for babies to have a second screening hearing test. This doesn't necessarily mean they have hearing loss. It may be because your baby was unsettled during the first test due to background noise or they may have a temporary blockage in their ear.
AABR test
During an AABR test, three small sensors will be placed on your baby's head and neck. Soft headphones will be put over your baby’s ears and quiet clicking sounds will be played through them. A computer will then be used to analyse how well your baby’s ears respond to the sound.
Other hearing tests are described below.
Visual reinforcement audiometry
During visual reinforcement audiometry (VRA), your baby will sit on your lap while sounds are played through speakers. If your baby turns towards the sound, a toy will be lit up as a reward.
The loudness and pitch of the sound will be varied to determine the quietest sound level your baby is able to hear at each pitch. This test is also carried out using tiny ear phones in your child’s ears so that each ear can be tested separately.
Play audiometry
Here, the child performs a simple task in response to a sound to show the tester that they have heard it. The sound can either be played through a speaker or an earphone.
The tests described below may be carried out if a problem with your child’s hearing is suspected.
Pure tone audiometry
During pure tone audiometry, a machine called an audiometer generates sounds at different volumes and frequencies.
Sounds are played through headphones and the child is asked to respond when they hear them – for example, by pressing a button. By decreasing the level of the sound, the tester can work out the quietest sounds that the child can hear.
Pure tone audiometry is only usually used for children who are over the age of four. It is often used to screen a child’s hearing before they start school.
Speech perception test
The speech perception test assesses a child’s ability to recognise words that they hear without being able to see a person move their lips.
Words can be played through headphones or through a speaker, or a person may say them directly to the child without showing their lips. The child will be asked to identify the words by picking out matching pictures or words on a list.
Tympanometry
Tympanometry is a test that shows how flexible the eardrum is. For good hearing, your eardrum needs to be flexible to allow sound to pass through it.
If the eardrum is too rigid – for example, because there is fluid behind it – sounds will bounce back off the eardrum instead of passing through it.
During the test, a small tube with a soft rubber tip will be placed at the entrance of your child's ear. The tube measures the sound that is bounced back from the ear.
If most of the sound is bounced back, it will indicate to the tester that your child's eardrum is rigid and that they may have a condition called glue ear (where fluid builds up inside the ear).
Vision tests
The eyes of newborn babies are checked for any obvious physical defects, including squints (where the eyes look in different directions), cloudiness (a possible sign of childhood cataracts) and redness.
Some of the tests that may be carried out are described below.
The pupil reflex test
The pupil reflex test involves shining a light into each of your baby’s eyes from a distance of 10cm to check the reflex of their pupils to light.
Your baby’s pupils should automatically shrink in response to the brightness of the light. If they don't, it suggests there is something affecting the reflex response of their pupils.
The red reflex test
The red reflex test involves using an instrument called an ophthalmoscope, which magnifies images and has a light at one end of it.
When light is shone into your baby's eyes, a red reflection should be seen as it is reflected back. If a white reflection is seen, it could be a sign of an eye condition such as cataracts. In this case, your baby will be referred to a specialist.
Attention to visual objects
This is a simple test to check whether a newborn baby pays attention to visual objects. A midwife or doctor will try to catch your baby's attention with an interesting object. They then move it to see if the child's eyes follow.
The rolling ball test
In older babies and toddlers of around two years of age, the focus and sharpness of their eyesight can be checked using the rolling ball test.
A number of different sized white balls are rolled across the floor and the tester checks whether the baby notices them. It shows the range of vision and how small an object your baby can spot.
Another simple test is to use small blocks or tiny objects like buttons to find out whether a child can see them and reaches for them. Each eye can be tested separately by covering the other one with a patch.
Snellen and LogMAR charts
After the age of six, charts that have rows of letters and numbers of decreasing sizes can be positioned at a distance of several metres. Your child will be asked to read out as many of the letters as they can see. These charts are called Snellen or logMAR charts.
Range of movement tests
To test the range of movement of each eye, a child's attention will be drawn to an interesting object, which is then moved to eight different positions: up, down, left, right, and halfway between each of these points.
The test involves checking how well each eye follows the object and how far the movement of the eye stretches in each direction.
Colour-blindness test
Colour blindness tests, also known as colour vision deficiency tests, are usually carried out at secondary school age if a problem is suspected.
Ishihara colour vision tests use images that are made up of dots in two different colours. If a child's colour vision is normal, they will be able to recognise a letter or number within the image.
A child who can't tell the difference between two colours won't be able to see the number or letter, which means that they may have a colour vision problem.
