Most of what we learn about the world around us comes from vision and hearing. And it's often not known that a people with sensory impairments still require regular sight and hearing tests. Most people who suffer from deafblindness or other sensory impairments retain some useful sight or hearing. These senses are vitally important so it's essential that a person can make the best use of any residual sight or hearing they have. Research indicates that it's best to diagnose and intervene in cases of deafblindness as early as possible in life. For children suffering from sensory impairments, an early diagnosis can provide a better chance to learn to use any residual sight or hearing they have and learn more about the world. There's a number of ways in which a deafblind person can be helped to use their residual sight or hearing. For example they could make use of a hearing aid, glasses, magnifiers or other specialist equipment. In many cases they can also benefit from adapting their home or environment, learning new skills and increasing their mobility. It's vital to obtain accurate information about a persons capacity for sight or hearing. And so regular testing is essential in identifying changes in hearing or sight which may require changes to equipment in the home or other environmental factors.
Research indicates that deaf children are more likely to develop problems with vision than hearing children. And given their heavy reliance on sight, identifying problems early is essential to ensure that any impairments are identified and rectified, if possible.
There's two main types of testing; clinical and functional testing. Clinical tests are usually carried out by a professional like an optician (who would perform an eye test) or an audiologist (who usually performs a hearing test). A clinical test uses standardised testing methods carried out under 'ideal' conditions in order to indicate how the sense is when compared to 'normal' levels or sight or hearing. Functional tests provide information on how somebody actually makes use of their sight or hearing. This test requires a range of stimuli and is carried out in a range of conditions. Functional testing can often expand on the information gathered during clinical testing.
There's a number of standardised tests for vision and each one deals with a different aspect of sight;
Near vision - This is typically tested by asking the person to read printed material in a number of different font sizes.
Distance Vision - This type of testing requires the participant to read letters of decreasing size from a chart placed around six metres away. An indication of the persons distance vision can be found by the size of the smallest letter they can read.
Field of vision - This testing involves looking straight ahead and then noting whether you can see objects or lights which appear at the side.
Examination of the inside of the eye - This test is carried out by use of an ophthalmoscope, which is a special kind of torch that allows your optician to shine a light into your eye and see the retina and the lens close up. Eye drops may be used in order to dilate the pupil in order to carry out a more thorough examination.
Examination of the outside of the eye - This usually involves the optician using a magnifying glass, pen torch or reading light in order to visually examine the outside of the eye. If a more detailed picture is required then a microscope may also be used.
Pressure Test - This test is performed using a tonometer. This machine blows puffs of air into the front of your eye and allows your optician to measure the pressure inside your eye.
Adjustable lenses and frames - If glasses will be of use then these can help the optician to find out which lenses are right for you. Several types of lens will be tried on each eye in order to find a combination which gives the best improvement in vision.
There's a number of unique problems which can come when testing the sight of a deafblind person. Problems with communication may mean that the person doesn't understand the testing. They could also lack certain skills which are needed for the test such as reading. Opticians aren't usually trained in working with people who have a dual sensory impairment and often don't provide the correct kind of testing. However, in many cases testing is still highly important and can still be carried out although allowances may have to be made to take the individuals circumstances into account. For some types of deafblindness, such as those suffering from Usher syndrome, normal standardised testing is still possible however in some cases different tests might be necessary. In some cases clinical testing alone won't provide an accurate picture of their sight impairment and so additional functional testing may be required.
Hearing loss is often slow to display symptoms so it's not always obvious that any loss has occurred. There are a number of signs which may indicate a person needs a hearing test including pain in the ears, discharge from the ear or difficulty hearing during a heavy cold. Those experiencing the onset of hearing loss frequently have the television or radio turned up loud and might not respond to normal sounds such as the telephone or doorbell. The onset of hearing loss can only be identified through an audiological test.
Tests for hearing loss are similar to eye tests in that they have both functional and clinical tests. Clinical tests for hearing are usually carried out under soundproof conditions by an audiologist. And this allows them to compare the hearing to 'normal' standards. In addition, it's also very important to test how the person uses their hearing and this requires more functional tests. If you suspect a hearing problem then at the first stage you should contact your GP. They can then examine you and determine whether the hearing loss is caused by wax, an ear infection or other temporary causes. If the hearing loss is not temporary then it's usual to be referred to an audiology department within a hospital. If someone is known to experience hearing problems then they should be tested annually. Those over the age of 60 should also have regular hearing tests. There's a wide variety of tests for hearing. Some require the person to co-operate and are called subjective tests, others measure hearing without co-operation and are known as objective tests. Some of the tests which might be used include;
Pure tone audiometry - This test involves a machine called an audiometer which produces accurately measured sounds in a range of pitches and volumes. Each ear is individually tested by using headphone and the person has to indicate the lowest level at which they can hear each pitch. The results are then marked on a chart or audiogram which is used to accurately measure hearing loss in each ear.
Free field audiometry - In this similar test both ears are tested together, meaning headphones aren't used. The test is generally performed in a soundproof room and can give an accurate indication of how well a person can hear in an everyday situation.
Bone conduction test - This test is used to show if the middle ear is impaired. A device called a bone conductor is placed behind the ear, resting on the mastoid bone. Signals are then passed directly to the cochlea or inner ear, bypassing the middle ear. If the cochlea appears to function normally then this may indicate the participant has middle ear deafness.
Distraction test - High and low pitched sounds are made at either side of the person's head. They indicate they have heard a sound by turning to look at the source.
Tympanometry - This test is conducted by an automatic examination of the middle ear by use of a probe which applies differing air pressure into the ear drum. The results of this test can help to identify the presence of a conductive hearing problem.
Evoked response test - This test involves a series of responses to sound by measuring brainwave activity through electrodes placed on the head. This is a subjective test and requires no responses from the participant.