Hearing and vision tests for children - How hearing and vision tests are performed

There are several tests that may be used to check your child's hearing and vision.

Newborn 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 (AOAE)
• automated auditory brainstem response test (AABR)

These are outlined below.

AOAE test

An AOAE 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 AOAE 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.

Hearing tests in older babies and children

A number of different hearing tests may be used to check for hearing problems in older babies and young children. These 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 earphones in your child’s ears so that each ear can be tested separately.

This test is usually used for children between six months and three years old.

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 usually only used for children who are over the age of three. It is often used to screen a child’s hearing before they start school, when it is sometimes referred to as the "sweep test".

Play audiometry

Play audiometry is similar to pure tone audiometry, but instead of pressing a button to indicate that they have heard sounds played through headphones or a speaker, the child is asked to perform a simple task. For example, they may be asked to move a toy each time they hear a sound.

This test is more commonly used in children under three years old.

Bone conduction test

Most of the tests above can also be carried out using a small vibrating device placed behind the ear, rather than sounds produced by headphones or speakers.

This device passes sound directly to the inner ear through the bones in the head, in order to identify which part of the ear isn't working properly if a child is having hearing problems.

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 and air is gently blown down it. 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.

As well as this examination, there are a number of tests that may be carried out to check for vision problems in babies and children. These 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.

Tests involving your child paying attention to objects can also be used to check the eyesight of older babies and young children who are not yet able to speak. If your child can speak, but is not yet able to recognise letters, pictures may be used instead of objects.

Snellen and LogMAR charts

When your child can recognise or match letters, their vision is tested using charts that have rows of letters and numbers of decreasing sizes. Your child will be asked to read out or match the letters they can see from a specific distance. 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. This tests each eye muscle in turn.

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.

One of the tests used to check for colour blindness is the Ishihara test. This involves looking at 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.

Colour blindness is much more common in males, with about one in every 14 being affected. The problem is very rare in females.

Read more about diagnosing colour blindness.