Infant Toddler Development Training
|Keratoconus diseases and disorders of the cornea|
|Glaucoma||abnormal increase in intraocular pressure|
|Color blindness||chromosomal abnormalities|
|Strabismus||eye muscle movement impairment results in incorrect eye alignment|
|Nearsightedness||lens/cornea curvature deficits|
|Cataracts||congenital infections or syndromes|
|Cortical blindness||closed head injuries, drowning, or meningitis all resulting in brain damage|
|(Heller, Alberto, Forney, & Schwartzman, 1996)|
Hearing impairment is any loss of hearing that affects a child's ability to access communication in their environment. Even mild and unilateral hearing loss will decrease a child's access to incidental language and communication opportunities. Severity of hearing loss is reported in decibel (dB) levels that refer to the loudness of a sound required for an individual to detect sounds of different frequencies (pitches). Mild hearing loss refers to a person who must have sound at least 26-40 dB loud before he or she can perceive that sound is present. A moderate degree of hearing loss occurs in a range of 41-55 dB, moderate-severe is 56-70 dB, severe is 71-90 dB, and profoundly deaf is defined as an inability to perceive sound, even when it is louder than 90 dB across the pitch range.
Hearing impairment is caused when physiological structures are damaged, deformed, or blocked. An ear canal plugged with ear wax or fluid or infection behind the eardrum will prevent a barrier to sound as it is conducted from the outer ear, to the inner ear. Thus, problems in the outer or middle ear cause conductive hearing losses. The cochlea within the inner ear is considered to be the sensory organ of hearing. When the hair cells that activate to the presence of sound in the inner ear are missing, damaged or deformed, the electrical signal that represents the sound cannot be transferred to the brain. Hearing loss due to problems with the hair cells in the inner ear is called a sensorineural hearing loss. Individuals can have problems in the hair cells of the cochlea and also have ear infections. Therefore, both sensorineural hearing loss and conductive hearing loss are present. In this situation the person will be said to have a mixed hearing loss. Hearing loss can also be progressive, requiring children with identified sensorineural hearing loss to have their hearing ability monitored every 3-6 months until school age. Finally, if the electrical signals generated in the cochlea to represent sound are not able to be processed, or cannot be processed effectively in the auditory cortex of the brain this is considered to be a central hearing loss, and more recently is called auditory dyssynchrony.
The incidence of permanent hearing loss in infants is 3/1000. Ear infections causing fluctuating conductive hearing loss are very common in infants and toddlers resulting in approximately 90% of children under the age of 3 having had at least one episode of ear infection, or otitis media.
|Disorders of the outer ear (Conductive loss)||Absence or closure of external ear canal Genetic inner ear abnormality Impacted ear canal (ear wax) Tumors Foreign bodies Swimmer's ear (infection of the skin of the external ear canal)|
|Disorders of the middle ear (Conductive loss)||Bacterial/viral infection Obstructed Eustachian tube Middle ear infection (otitis media) Head trauma|
|Disorders of the inner ear and auditory nerve (Sensorineural loss)||Congenital infections (Usher's syndrome) Trauma Loud noises Meningitis Damage to cochlea or auditory nerve|
|Disorders of the outer, middle, and inner ear (Mixed hearing loss)||(All of the above causes can be considered for a mixed hearing loss)|
|Disorders of the central auditory system (Central hearing loss)||Auditory dyssynchrony Brain tumors Acquired brain damage Vascular changes in the brain|
|Adapted from: (Heller, Alberto, Forney, & Schwartzman, 1996)|