Types of Disabilities

 In order to appreciate the depth and magnitude of PWD, it is important to identify the various categories of impairment from which challenges can be explored. Some of the popular impairments are visual, hearing, physical speech, emotional and intellectual.

Visual impairment

Visual impairment represents a continuum, from very poor vision, to people who can see light but no shapes, to people who have no perception of light at all.

Low vision is defined as vision that is between 20/40 and 20/200 after correction. (20/200 means that something at 20 feet would be just as visible as something at 200 feet would be to someone with normal 20/20 vision). 

A person is termed legally blind when their visual acuity (sharpness of vision) is 20/200 or worse after correction, or when their field of vision is less than 20 degrees. Blindness can be present at birth, acquired through illness or accident, or associated with ageing (glaucoma, cataracts, macular degeneration, optic nerve atrophy, diabetic retinopathy).

According to the American Foundation for the Blind, almost 1 person in every 1,000 under age 45 has a visual impairment of some type, while 1 in every 13 individuals older than 65 has a visual impairment which cannot be corrected with glasses. With current demographic trends toward a larger proportion of elderly, the prevalence of visual impairments will certainly increase.

Hearing impairment

Hearing impairments are classified into degrees based on the average hearing level for various frequencies (pitches) by decibels (volume) required to hear, and also by the ability to understand speech. Loudness of normal conversation is usually 40-60 decibels. 

A person is considered deaf when sound must reach at least 90 decibels (5-10 times louder than normal speech) to be heard, and even amplified speech cannot be understood, even with a hearing aid (Olusanya, Bamigboye & Somefun, 2012).

Hearing impairment may be Sensorineural or conductive. Sensorineural involves damage to the nerves used in hearing (i.e., the problem is in transfer from ear to brain). Causes include ageing, exposure to noise, trauma, infection, tumours and other disease. 

Conductive hearing loss is caused by damage to the ear canal and mechanical parts of the inner ear. Causes include birth defects, trauma, foreign bodies or tumours (Gopinath et al., 2012).

Hearing impairments can be found in all age groups, but loss of hearing acuity is part of the natural ageing process. The number of individuals with hearing impairments will increase with the increasing age of the population and the increase in the severity of noise exposure (Freeland, Jones & Mohammed, 2010).

Speech impairment

Disorders in speech are an impairment of the articulation of speech sounds, fluency, and or voice (ASHA Ad Hoc Committee on Service Delivery in the Schools, 1993). Speech impairment includes any symptom that causes an adult to have difficulty with vocal communication.

Such problems may include slurred, slowed, hoarse, stuttered, or rapid speech. Other symptoms may include stiff facial muscles, drooling, poor accessibility of words, and sudden contraction of vocal muscles.

Speech impairment can occur suddenly or can gradually progress. Each speech impairment type has a different cause, which is what sets it apart. Some of the popular forms of speech impairment include spasmodic dysphonia, aphasia, dysarthria, and vocal disturbances (Ashley, Duggan & Sutcliffe, 2006).

Emotional disturbance/impairment

Emotional disturbance/impairment means a condition exhibiting one or more of the following characteristics over a long period of time and to a marked degree that adversely affects a child’s educational performance: an inability to learn that cannot be explained by intellectual, sensory, or health factors; an inability to build or maintain satisfactory inter- personal relationships with peers and teachers; inappropriate types of behavior or feelings under normal circumstances; a general pervasive mood of unhappiness or depression and a tendency to develop physical symptoms or fears associated with personal or school problems. 

Emotional disturbance/impairment includes schizophrenia (Federal Register, 2006, p. 46756). Emotional impairment may be explained by (a) biological factors, such as genetics, brain damage or dysfunction, malnutrition and allergies, temperament, or physical illness; (b) family factors, such as the family definition and structure, family interaction, family influences on school success and failure, and external pressures affecting families; and (c) school factors, such as deficiencies in the ability of school personnel to accommodate students’ variable intelligence, academic achievement, and social skills (Kauffman, 2001).

Intellectual impairment

Intellectual disability (ID) or general learning disability is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors. Intellectual disability is also known as mental retardation (MR), although this older term is being used less frequently in some areas and even being eliminated in others altogether. 

Intellectual disability is subdivided into syndromic intellectual disability; in which intellectual deficits associated with other medical and behavioral signs and symptoms are present, and non-syndromic intellectual disability, in which intellectual deficits appear without other abnormalities. The signs and symptoms of intellectual disability are all behavioural. Most  people with intellectual disability do not look like they are afflicted with such, especially if the disability is caused by environmental factors such as malnutrition or lead poisoning. The so-called typical appearance ascribed to people with intellectual disability is only present in a minority of cases, all of which are syndromic.

Children with intellectual disability may learn to sit up, to crawl, or to walk later than other children, or they may learn to talk later and in about one-third of children, the causes of intellectual impairments are unknown (Daily, Ardinger & Holmes, 2000). 

Low supply of iodine, problems during birth (e.g., low oxygen), exposure to some diseases such as whooping cough, malnutrition, alcohol consumption during pregnancy.

Ref: GSS (October 2014)