Types of sight and hearing loss

Combined sight and hearing loss involves an impairment of both senses, without a specific level of sight and / or hearing loss. The impact of these impairments is how we define deafblindness.

Sight loss

Sight loss which is sometimes called visual impairment or loss has an impact on most aspects of our daily lives, our sight for example enables us to get out and about whether on foot, public transport, or car.

There are two types of sight loss, being loss of visual acuity and loss of peripheral vision it is though possible to have both types of loss at the same time.

Acuity

Snellan Chart

Acuity is the clarity of our vision, it is our ability to recognise details, faces, to read text, and watch television. This can also be referred to as the sharpness of our vision.

Most people will recognise the Snellen chart, as the capital letters we are asked to read in the opticians or at the ophthalmologist. This chart is used to test our visual acuity, whilst we are fixating (looking) at the letters of the chart using our central vision.

The test is an important part of any sight loss exam, and can be used to identify the prescription for any glasses as well as being an essential part of certifying a person with sight loss.

Some common acuity sight loss conditions are Age-Related Macular Degeneration, Cataracts, and both long and short sightedness.

Peripheral

Our peripheral vision is also known as our side vision;, a reduction in this vision affects our independent mobility, locating objects or people, depth perception and can effect our balance. The central vision remains intact, with a reduction in the vision to either side, above or below the eye level. This loss can cause a tunnel type effect where only the very central vision remains – this is often called ‘tunnel vision’.

The peripheral vision is measured by an optician or ophthalmologist using a visual field test, which tests for areas in which the vision is reduced. This loss can then be measured in degrees of visual field remaining. The test is a important part of any sight loss exam, especially from the age of 30 or where there is a immediate family history of glaucoma as the incidence increases with age and is genetically hereditary. A visual field test is also an essential part of certifying a person with sight loss.

Some common causes of peripheral sight loss are Retinitis Pigmentosa (RP), Glaucoma, and Retinal Detachment.

Hearing loss

A hearing loss is when your ability to hear is reduced, making it more difficult for to hear speech and other sounds. In most cases a hearing loss cannot be cured, but may be treated by the use of a hearing aid, or another hearing appliance such as a cochlear implant. It is also possible to experience a hearing impairment as a result of conditions such as tinnitus which impair the hearing process despite not being a cause of a hearing loss.

There are two types of hearing loss, conductive and sensorineural, it is possible to experience both types of loss at the same time this is a mixed hearing loss.

Conductive

A conductive hearing loss is general loss of volume, where all sounds seems faint or muffled. It is where the ears’ ability to conduct sound from the outer ear through the middle ear into the inner ear is blocked or reduced, often impacting the lower frequencies more significantly.

An audiologist can test your hearing to identify the severity of the loss, and identify any potential causes. Where they considered your results to require further investigation or treatment such as hearing aids, they can refer you for further appointments such as with the Ear, Nose and Throat (ENT team).

Conductive hearing loss is caused by problems within the ear canal, ear drum, or the middle ear including the middle ear bones. There is no main significant cause of conductive hearing loss. Where a child is born with a conductive hearing loss the cause is usually genetic or linked to their development in the womb which can include malformation of any part from the outer to middle ear. Causes after birth are wide ranging, they include temporary loss from fluid in the middle ear from a cold, ear infection (middle ear and ear canal), Eustachian tube malfunction, impacted ear wax, perforated ear drum and Otosclerosis (can be a mixed hearing loss, and may be genetic).

Sensorineural

A sensorineural hearing loss is a loss of specific sound frequencies. This can be limited frequencies or apply to all frequencies. Sensorineural hearing loss is a term to cover two different situations where the loss is caused within the cochlear (inner ear) or is caused by the hearing nerve, the most likely cause is damage or malformation of the cochlear.

An audiologist can test your hearing to identify the severity of the loss, and identify any potential causes. Where they considered your results to require further investigation or treatment such as hearing aids, they can refer you for further appointments such as with the Ear, Nose and Throat (ENT team).

Sensorineural hearing loss is most commonly caused by damage to the hair cells within the cochlear in the inner ear. These cells can be abnormal at birth or damaged during your lifetime. Where a child is born with a sensorineural hearing loss the cause is usually genetic or linked to their development in the womb. Causes after birth are wide ranging, they include trauma, presbycusis (age-related loss), overexposure to noise, exposure to sudden extremely loud noises, ototoxic medications, infectious diseases such as meningitis and some genetic conditions.

Testing for hearing loss

To test an adult for any hearing loss an audiologist, may complete a series of tests during an appointment which can also identify the type and potential causes of a hearing loss. Some of the common tests include;

  • Pure tone audiometry. This is the test many people will recognise as a hearing test. You sit within a soundproof room and listen to a series of different sounds usually types of a beep, through headphone and press a button each time you hear a sound. The audiologist via a computer sends the sounds to the headphones and records the response to produce an audiogram a visual picture of your hearing loss showing frequencies and decibel of sound loss. A similar beep test may also be completed using a sound next to the skull behind the ear, this identifies if there is a difference between two types of conduction, air what we can hear normally and bone what we can hear if sounds are transmitted directly through the bones.
  • Speech perception. This test is similar to the pure tone, but speech is listened to rather beeps or other tones. The test is important as a hearing loss may appear significant but the persons ability to determine speech sounds is good, this information is used in determining any treatment options.
  • This test places a small device is placed in your ear to check for fluid behind your eardrum, it measures a response to changing pressure in the ear. The test can help identify if fluid is causing a conductive hearing loss.

If you would like to learn about how to get a Deafblind assessment, please click here