Lesser Known Disorders
Each issue of this series contains at least three lesser known disorders. Some of these disorders may contain subtypes which will also be presented. You will also notice that each disorder has a code. These codes represent the coding system for all disabilities and disorders listed in the Educator’s Diagnostic Manual(EDM) Wiley Publications.
Disorders in this issue:
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VI 2.00 – Corneal Dystrophies of the Eye
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LD 10.00-Sensory Integration Disorders
VI 2.00 Corneal Dystrophies of the Eye
Disability Category- Visual Impairments
Definition
Corneal dystrophies form a group of rare disorders which usually affect both eyes. They may be present at birth, but more frequently develop during adolescence and progress gradually throughout life. Some forms are mild, others severe (Royal National Institute for the Blind, 2005).
Diagnostic Symptoms
Corneal dystrophies affect vision in widely differing ways. Some cause severe visual impairment, while a few cause no vision problems and are discovered during a routine eye examination. Other dystrophies may cause repeated episodes of pain without leading to permanent loss of vision (National Eye Institute, 2005e).
Further Key Points
These diseases share many traits, including:
- They are usually inherited.
- They affect the right and left eyes equally.
- They are not due to the effects of outside factors, such as injury or diet.
- Most progress gradually.
- Most usually begin in one of the five corneal layers and may later spread to nearby layers.
- Most do not affect other parts of the body, nor are they related to diseases affecting other parts of the eye or body.
- Most can occur in otherwise totally healthy people, male or female.
- Corneal dystrophies affect vision in widely differing ways. Some cause severe visual impairment, while a few cause no vision problems and are discovered during a routine eye examination. Other dystrophies may cause repeated episodes of pain without leading to permanent loss of vision.
Types of Corneal Dystrophies of the Eye
VI 2.01-Bietti’s Crystalline Dystrophy
Definition
Bietti’s crystalline dystrophy (BCD) is an inherited eye disease. (National Eye Institute, 2005e).
Explanation
Bietti’s crystalline dystrophy (BCD) named for Dr. G. B. Bietti, an Italian ophthalmologist, who described three patients with similar symptoms in 1937. The symptoms of BCD include: crystals in the cornea (the clear covering of the eye); yellow, shiny deposits on the retina; and progressive atrophy of the retina, choriocapillaries and choroid (the back layers of the eye). This tends to lead to progressive night blindness and visual field constriction. BCD is a rare disease and appears to be more common in people with Asian ancestry.
People with BCD have crystals in some of their white blood cells (lymphocytes) that can be seen by using an electron microscope. Researchers have been unable to determine exactly what substance makes up these crystalline deposits. Their presence does not appear to harm the patient in any other way except to affect vision.
From family studies, we know that BCD is inherited primarily in an autosomal recessive fashion. This means that an affected person receives one nonworking gene from each of his or her parents. A person who inherits a nonworking gene from only one parent will be a carrier, but will not develop the disease. A person with BCD syndrome will pass on one gene to each of his or her children. However, unless the person has children with another carrier of BCD genes, the individual’s children are not at risk for developing the disease (National Eye Institute, 2005e).
VI 2.02-Lattice Dystrophy
Definition
Lattice dystrophy gets its name from an accumulation of amyloid deposits, or abnormal protein fibers, throughout the middle and anterior stroma (National Eye Institute, 2005).
Explanation
During an eye examination, the doctor sees these deposits in the stroma as clear, comma-shaped overlapping dots and branching filaments, creating a lattice effect. Over time, the lattice lines will grow opaque and involve more of the stroma. They will also gradually converge, giving the cornea a cloudiness that may also reduce vision.
In some people, these abnormal protein fibers can accumulate under the cornea’s outer layer—the epithelium. This can cause erosion of the epithelium. This condition is known as recurrent epithelial erosion. These erosions: (1) Alter the cornea’s normal curvature, resulting in temporary vision problems; and (2) Expose the nerves that line the cornea, causing severe pain. Even the involuntary act of blinking can be painful.
Although lattice dystrophy can occur at any time in life, the condition usually arises in children between the ages of two and seven (National Eye Institute, 2005).
VI 2.03-Keratoconus
Definition
Keratoconus is a progressive thinning of the cornea—is the most common corneal dystrophy in the U.S., affecting one in every 2000 Americans (National Eye Insitute, 2005).
Explanation
It is more prevalent in teenagers and adults in their 20s. Keratoconus arises when the middle of the cornea thins and gradually bulges outward, forming a rounded cone shape. This abnormal curvature changes the cornea’s refractive power, producing moderate to severe distortion (astigmatism) and blurriness (nearsightedness) of vision. Keratoconus may also cause swelling and a sight-impairing scarring of the tissue.
In most cases, the cornea will stabilize after a few years without ever causing severe vision problems. But in about 10 to 20 percent of people with keratoconus, the cornea will eventually become too scarred or will not tolerate a contact lens. If either of these problems occur, a corneal transplant may be needed. This operation is successful in more than 90 percent of those with advanced keratoconus. Several studies have also reported that 80 percent or more of these patients have 20/40 vision or better after the operation (National Eye Insitute, 2005).
VI 2.04-Map-Dot-Fingerprint Dystrophy
Definition
This dystrophy occurs when the epithelium’s basement membrane develops abnormally (the basement membrane serves as the foundation on which the epithelial cells, which absorb nutrients from tears, anchor and organize themselves). When the basement membrane develops abnormally, the epithelial cells cannot properly adhere to it. This, in turn, causes recurrent epithelial erosions, in which the epithelium’s outermost layer rises slightly, exposing a small gap between the outermost layer and the rest of the cornea (National Eye Institute, 2005).
Explanation
Epithelial erosions can be a chronic problem. They may alter the cornea’s normal curvature, causing periodic blurred vision. They may also expose the nerve endings that line the tissue, resulting in moderate to severe pain lasting as long as several days. Generally, the pain will be worse on awakening in the morning. Other symptoms include sensitivity to light, excessive tearing, and foreign body sensation in the eye (National Eye Institute, 2005).
VI 2.05-Non Corneal Dystrophy-Retinal Stargardt’s Macular Dystrophy
Definition
Stargardt’s Macular Dystrophy is an inherited condition that affects the macula; an area of the central retina (Royal National Institute of the Blind, 2005).
Explanation
Conditions involving the macula affect central vision. Although there may be considerable sight loss, in some cases to levels where registration would be offered, total loss of sight is rare. Decreased central vision is usually the first symptom of Stargardt’s Macular Dystrophy and visual loss is progressive over a period of years, sometimes to a level of 6/60 (Royal National Institute of the Blind, 2005).
LD 10.00-Sensory Integration Disorders
Disability Category – Specific Learning Disabilities
Definition
Although sensory disorders can be present in any child, studies indicate that approximately 70% of children with learning disabilities have sensory issues (Childhood Anxiety Network, 2005).Sensory integration disorder or dysfunction (SID) is a neurological disorder that results from the brain’s inability to integrate certain information received from the body’s five basic sensory systems. These sensory systems are responsible for detecting sights, sounds, smell, tastes, temperatures, pain, and the position and movements of the body. The brain then forms a combined picture of this information in order for the body to make sense of its surroundings and react to them appropriately (Kapes, 2002).
Diagnostic Symptoms
Diagnostic symptoms of Sensory Integration Disorders include (Childhood Anxiety Network, 2005):
- Over or under sensitive to sound (e.g., child may cover ears and pull away from most noises or crave a lot of multiple sound stimuli).
- Overly sensitive or under sensitive to lights (e.g., child covers their eyes and may not be able to tolerate bright lights or flashing lights ).
- Under-reactive to sensory stimulation (e.g., child craves spinning, jumping, moving constantly -or- has difficulty with most movement stimul).
- Unusually high or low activity level; may seem hyperactive or hypoactive.
- Coordination problems; may seem clumsy or careless.
- Delays in speech, language, motor skills.
- Below par academic performance.
- Poor organization of behavior (e.g., impulsive, distractible, frustrated, aggressive)
- May seem lazy, bored, or unmotivated:
- Difficulty making transitions. Child has difficulty with routine changes, difficulties with season changes (e.g., going from shorts to pants and vice versa)
- Social and/or emotional problems (e.g., acts out, has frequent temper tantrums, or seems
- Easily distracted
- Physical clumsiness or apparent carelessness
- Inability to unwind or calm self
- Poor self concept
Further Key Points
The ongoing relationship between behavior and brain functioning is called sensory integration (SI), a theory that was first pioneered by A. Jean Ayres, Ph.D., OTR in the 1960s (Kapes, 2002).
While research indicates that sensory integrative problems are found in up to 70% of children who are considered learning disabled by schools, the problems of sensory integration are not confined to children with learning disabilities. SID transfers through all age groups, as well as intellectual levels and socioeconomic groups. Factors that contribute to SID include: premature birth; autism and other developmental disorders; learning disabilities; delinquency and substance abuse due to learning disabilities; stress-related disorders; and brain injury. Two of the biggest contributing conditions are autism and attention-deficit hyperactivity disorder (Kapes, 2002).
Types of Sensory Integration Disorders
LD 10.01-Tactile Defensiveness Sensory Integration Disorder (Immature Tactile Type)
Definition
A type of sensory integration disorder specifically associated with difficulties in being touched because of an immature tactile system (Sensory processing disorder.com). Tactile defensiveness refers to a pattern of observable behavioral and emotional responses, which are aversive, negative and out of proportion, to certain types of tactile stimuli that most people would find to be non-painful (Chu, 2000).
Explanation
The tactile system is our sense of touch through different sensory receptors in our skin. We say that a child is “tactile defensive” when he or she is extremely sensitive to light touch.
One important role of our tactile system is its protective function that alerts us when something is unpleasant or dangerous. For some children, this function of the tactile system is not working normally. They may perceive most touch sensations to be uncomfortable or scary and react with a flight-or-flight response (Chu, 2000).
Theoretically, when the tactile system is immature and working improperly, abnormal neural signals are sent to the cortex in the brain which can interfere with other brain processes. This, in turn, causes the brain to be overly stimulated and may lead to excessive brain activity, which can neither be turned off nor organized. This type of over-stimulation in the brain can make it difficult for an individual to organize one’s behavior and concentrate and may lead to a negative emotional response to touch sensations Hatch-Rasmussen, 2001).
Often, children with tactile defensiveness will avoid touching the following (Sensory processing disorder.com):
- textured materials/items
- “messy” things
- vibrating toys, etc.
They may also be significantly bothered by, and avoid the following:
- a hug
- a kiss
- certain clothing textures
- seams on socks
- tags on shirts
- light touch or
- their hands being dirty
LD 10.02- Proprioceptive Perceptual Sensory Integration Disorder
Definition
A type of sensory integration disorder specifically associated with difficulties knowing where one is in space. It is the sense of the position of our body parts in relation to our own bodies (Learning Disabilities Association, 2005; Hatch-Rasmussen, 2001)
Explanation
The proprioceptive sense is the sense of the position of our body parts in relation to our own bodies. This information is essential to coordinate and integrate movement because it allows us to know where we are in space. According to Hatch-Rasmussen (2001), the proprioceptive sense is responsible for providing the body with the necessary signals to allow us to sit properly in a chair or to step off a curb smoothly. Some common signs of proprioceptive dysfunction are:
- a lack of awareness of body position in space
- a tendency to fall
- clumsiness
- difficulty manipulating small objects
- eating in a sloppy manner
- minimal crawling when young
- odd body posturing
- resistance to new motor movement activities (Hatch-Rasmussen, 2001).
LD 10.03-Tactile Pressure Sensory Integration Disorder
Definition
A type of sensory integration disorder specifically associated with difficulties in judging the appropriate amount of pressure needed to perform motor acts (Learning Disabilities Association, 2005).
Explanation
Children with Tactile Pressure Sensory Integration Disorder have trouble judging the right amount of pressure needed to perform motor acts. Examples of tactile pressure include holding an egg in two fingers without breaking or dropping it, tapping someone playfully rather than hitting him/her, strumming a guitar softly, and pushing an elevator button with the right amount of pressure.
LD 10.04- Vestibular Dysfunction Sensory Integration Disorder
Definition
A type of sensory integration disorder specifically associated with difficulties in processing information coming from the vestibular receptors located inside the ears (Packer, 2004).
Explanation
Vestibular processing refers to the information that is provided by the receptors within the inner ear. These receptors are stimulated by movement of the head and input from other senses. This input tells where we are in relation to gravity, whether we are still or moving, how fast we are going, and in which direction. It also influences the development of balance, equilibrium, postural control and muscle tone.
If a child’s vestibular system doesn’t develop or integrate normally, she may be hypersensitive to ordinary childhood activities such as swinging on swings, going down slides, etc. She may also experience difficulty walking on or negotiating nonlevel surfaces such as hills or stairs. Children with this kind of hypersensitive vestibular system often appear clumsy. But not all children with vestibular dysfunction are hypersensitive. Some are under- or hyposensitive. Children with hyposensitive vestibular systems often engage in what appears to be sensation-seeking behaviors. They may whirl around like a dervish, jump, and/or spin (Packer, 2004).
According to Hatch-Rassmusen (2001), symptoms of students with Vestibular Dysfunction Sensory Integration Disorder include:
- Becomes over-excited watching other children moving
- Craves or avoids movement
- Creates self movement-i.e. rocking, moving or re-positioning in chair
- Daredevil behaviors
- Decreased attention to task
- Dislikes upside down play
- Erratic arousal level
- Fear of going up/down stairs
- Fearful when feet leave the ground
- In constant motion
- Poor or decreased balance skills
- Putting head in upside down position or rapid head turning/shaking
- Running or moving about quickly
- Spinning self or objects
- Toe walking
- Up and down out of seat frequently or falling off of chair.
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