Newborn babies are usually screened using two quick and simple tests to see if further investigation is needed:
- Automated Otoacoustic Emissions test (OAE), and
- Automated Auditory Brainstem Response test (AABR).
Both tests are painless for your baby.
Automated Otoacoustic Emission (AOAE) test
A tiny earpiece is placed in the baby's outer ear and quiet clicking sounds are played through it. This should produce reaction sounds (echoes) in a part of the ear called the cochlea, which a computer can record and analyse. The test can be done while the baby is asleep, and it only takes a few minutes.
Sometimes, the results from the AOAE test are not clear. In this case, the test may be done again or a different test called the Automated Auditory Brainstem Response (AABR) can be used.
It is common for babies to have a second screening hearing test. This does not necessarily mean they have hearing loss. It may be because your baby was unsettled due to background noise or a temporary blockage in their ear.
Automated Auditory Brainstem Response (AABR) test
Three small sensors are placed on your baby's head and neck. Specially designed soft headphones are then placed over your baby's ears and quiet clicking sounds are played through the earphones. A computer analyses how well your baby's ears respond to the sound. The AABR test can take between 5 and 30 minutes.
Other hearing tests that may be given to your child include:
Infant distraction test
An infant distraction test may be carried out during your baby's routine health check-ups. Your baby sits on your lap while one tester keeps their attention visually. The other tester makes various sounds around the baby and watches to see if they turn towards the sound.
The theory is, if hearing is normal, the child will turn their head to respond to the noise. It is not a very accurate test and other things can influence the result, such as your baby's interest in the type of sound and poor vision.
The child performs a simple task in response to sound to show the tester that they have heard it. The sound can either be played through a speaker or an earphone.
Pure tone audiometry
A machine called an audiometer generates sounds at different volumes and frequencies. Sounds are played through headphones and a 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. This test is only usually used for children over four years of age and is often used to screen your child's hearing before they start school.
Speech perception test
This 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 a speaker, or a person may say them directly to the child without showing their lips. The child will then have to identify the words by picking out matching pictures or words on a list.
This test 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 if there is fluid or 'glue' behind it, the sounds bounce back off the eardrum instead of passing through it.
A small tube with a soft rubber tip is placed at the entrance to the ear. This measures the sound that is bounced back from the ear. If most of the sound is bounced back, the tester will know that the eardrum is rigid and that your child may have glue ear, a condition where fluid builds up in the middle ear.
The eyes of newborn babies are examined for any obvious physical defects, including squints, cloudiness (a sign of cataracts) and redness. Tests that may be done include:
The pupil reflex test
The pupil reflex test is done by shining a light into each of your baby's eyes from a distance of 10cm. It checks the reflex of their pupils to light.
Your baby's pupils should automatically shrink in response to the brightness of the light. If they do not, it suggests there is something affecting the reflex response of their pupils.
The red reflex test
This test is carried out using a magnifying instrument with a light on the end called an ophthalmoscope. Light is directed into your baby's eyes and a red reflection should be seen as the light is reflected back. If the reflection is white instead of red, your child will be referred to a specialist. This response can be a sign of eye conditions such as cataracts.
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 a 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 up to two years, the focus and sharpness of eyesight can be checked using the rolling ball test. Differently sized white balls are rolled across the floor. 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 with a patch.
Snellen and LogMAR charts
After six years of age, charts with rows of letters and numbers of decreasing sizes can be held up at a distance of several metres. A child is asked to read out as many of the letters as they can see. These charts are called Snellen charts or logMAR cards.
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 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 (colour vision deficiency) tests are usually carried out at secondary school age if a problem is suspected. Ishihara colour vision tests involve images made up of dots in two different colours. If colour vision is normal, the child will be able to recognise the letter or number that is highlighted in the image. A child who cannot tell the difference between two colours (such as red and green) will not be able to see the number or letter highlighted and may have a colour vision problem.