Dual sensory impairment as a peripheral impairment
Dual sensory impairment caused by disorders in the peripheral parts of both systems, eyes and ears, is uncommon in children. The changes in the peripheral parts of the visual system are structural changes in the eyes and optic nerves and in the auditory system structural changes in the outer, middle and/or inner ear. There are two different groups among these children based on their communication and educational needs:
1) Children with congenital infections (rubella, toxoplasmosis, syphilis, CMV, herpes meningitis, encephalitis), rare syndromes or an unknown cause that has affected development of both eyes and ears, is one group. This group of children has a great variation in their communication techniques. Many depend on tactile sign language, many have limited language skills but there are also children with normal spoken language and good, although stressful communication using hearing aids and trying to decipher visual communication. Severity of brain damage varies and is difficult to assess during the first and second year because we cannot be sure about the degree and type of deprivation.
2) Children who have hearing impairment from early on and develop visual symptoms later. Usher syndrome is the most common cause of this type of combined loss of vision and hearing. In communication these children use hearing aids, speech, visual sign language, speech reading and body language. Vision loss is gradual and visual communication usually remains fairly good through school age. Children who had hearing in preschool age and learned to speak can now get a cochlear implant in many countries when their progressing hearing loss is no longer helped with hearing aids.
Deaf infants are receiving cochlear implants very early.
If both vision and hearing are impaired from birth, the child and his parents need intensive training in interaction, communication and exploration. The communication techniques of this group of children vary so much that the early
intervention teams and teachers need to have good information from the medical experts, psychologists and optometrist who in turn need to know this special population.
with coloboma and hearing impairment
If a child with hearing impairment has large colobomas in both eyes like the infant in the video below, it is often difficult for them to get adequate visual information from the lips of people who are speaking. The central retina is often pulled upward from its normal location. Therefore, when the infant is looking at the adult person’s face, he seems to be looking at or above the hairline. This is naturally disconcerting to those interacting with the child, as they may feel that he is not looking at them and this can pose a further challenge to the development of communication unless it is explained clearly.
The next photo shows how the therapist gently guides the infant to study his legs and feet with his hands. Note that the infant also looks in the direction of his feet when touching them. At a moment that the therapist felt good for testing, a high contrast toy (seen in the next photo) was slowly moved in front of the infant who followed it with combined head and eye movements 180 degrees.
The responses had three observers: the therapist, her consulting experienced therapist (the NDT therapist behind the camera) and the ophthalmologist (giving the test object, a high contrast ring).
Video recording of test situations like this gives useful material for follow-up of the development. This infant with large colobomas had been assessed as totally blind the day before. The parents of infants with syndromes that cause loss of vision and large anatomic changes in the eyes, nearly always hear “this infant is not going to see.”
Toddlers and children with moderate to severe impairment of vision and poor hearing because of rare syndromes may have intellectual disabilities but may as well have normal intelligence and may develop compensatory functions so that they often seem to see better than they really do. They use cues that they pick in the environment to remember their routes, keep their devices and toys well arranged to find them with ease. Therefore they may be required to function at a much higher visual level than where they actually are.
In school, apart from the challenges of keeping up in the classroom, it is important to recognize that the break time can be very stressful for children with vision and hearing impairment. The noise levels increase and the movements of children are greater, faster and more unpredictable than at any other time of the day. Provisions should be made so that these children have the opportunity to have access to a quieter space for at least some parts of the day to enable them to recharge their energies.
Toddlers and young children, who do not start to talk, are taught using various communication strategies. Sign language is used in many countries to support delayed development of speech, or as an alternative to speech, but is not accepted in all countries or some communities of a country as a technique of expressive language. In these places, hearing-impaired children, for example, are asked to learn speech reading although it has not been examined, whether the children can perceive lip movements. This should be tested in all children before starting to train speech reading. Picture communication may also be started before perception and recognition of pictures has been assessed. Thorough assessment of visual functions should, actually MUST be a prerequisite for choosing communication techniques.
Children with Usher’s Syndrome are a special group among the deaf-blind children.
Most of them are born with a severe hearing defect but some have useful hearing until school age (Usher syndrome type III) and then develop progressive sensory-neural hearing defects. Visual impairment is caused by congenital retinal degeneration that starts to cause symptoms before or in school age. The first symptom is often “night blindness” (actually not blindness but slow adaptation to low luminance levels), which can be diagnosed during the first year by observing the infant in daylight and twilight.
Changes in the visual field start as small islands of decreased sensitivity, slowly become confluent and form a ring scotoma, a ring-shaped poorly functioning area around the central visual field. Peripheral vision disappears very slowly and a limited central field of vision usually remains until adulthood or even past 60 years. Photophobia and continuous flickering in the visual image bother some of these children. A young child seldom notices his visual problems before they are explained to him because he does not know how other people see. Vision development in all deaf and hard of hearing children should be followed for possible changes as a part of school health.
The confirmation of the diagnosis of Usher syndrome can be made in eye hospitals with electroretinography by measuring the responses of the retina to different stimuli.
Functional diagnosis of a delay in the adaptation time of the cone cells is possible early with the CONE Adaptation test (Good-Lite) that measures the time needed to start seeing in twilight. The measurement takes less than twenty seconds, and the instructions to the child, just a few minutes. It is important to be aware of the delay in cone adaptation so that the child gets a good torch/flashlight when sent to get something from a dark place and extra lamps in the closets. Extra lamps outside the house and strategies for moving in twilight using a torch, later with a cane, help these children in developing a full participation and independent moving.
The assessment of progressive visual defects requires ability to communicate with deaf children. To improve the assessment situations, all deaf children should learn the basic vocabulary related to vision and vision examination but also the testers should learn at least rudimentary communication using signs during assessments. Deaf children with normal vision also need this information to understand their deaf-blind peers.
Central auditory and visual processing disorders
A combined processing disorder is rare but should be remembered when assessing children with brain damage. A brain damage can affect processing of both visual and auditory information. Functions of eyes and ears and the pathways may be normal but the processing of information has defects. Dual central processing disorders are usually a part of an extensive brain damage but can also occur in otherwise normally developing children with mild or no motor problems.
If an infant has learned to move at the appropriate age, finds his way in the house and on the yard and seems to hear even the weakest sounds, most people do not notice that the child does not have any interest in toys, except knocking them, does not recognize family members or facial expressions, has never copied gestures and does not speak a word. If the parents express worries to doctors, the diagnosis of “autism” is regularly given because it is so much more common than dual loss of processing functions. There are few places were correct diagnoses can be given during the first or second year, and thus, sensory deprivation and lack of communication may make the child frustrated and angry.