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:
VI – 3.16- Retinopathy of Prematurity (ROP)
Disability Category: Visual Impairment
Definition
Retinopathy of prematurity (ROP) is a potentially blinding eye disorder that primarily affects premature infants weighing about 2¾ pounds (1250 grams) or less that are born before 31 weeks of gestation (A full-term pregnancy has a gestation of 38–42 weeks) (National Eye Institute, 2005).
Explanation
The smaller a baby is at birth, the more likely that baby is to develop ROP. This disorder—which usually develops in both eyes—is one of the most common causes of visual loss in childhood and can lead to lifelong vision impairment and blindness. ROP was first diagnosed in 1942.
ROP occurs when abnormal blood vessels grow and spread throughout the retina, the tissue that lines the back of the eye. These abnormal blood vessels are fragile and can leak, scarring the retina and pulling it out of position. This causes a retinal detachment. Retinal detachment is the main cause of visual impairment and blindness in ROP.
ROP is classified in five stages, ranging from mild (stage I) to severe (stage V). Most babies who develop ROP have stages I or II. However, in a small number of babies, ROP worsens, sometimes very rapidly. Untreated ROP threatens to destroy vision (National Eye Institute, 2005).
ROP is classified in five stages, ranging from mild (stage I) to severe (stage V):
VI 3.16a Stage I -Mildly abnormal blood vessel growth.
Many children who develop stage I improve with no treatment and eventually develop normal vision. The disease resolves on its own without further progression.
VI 3.16b Stage II-Moderately abnormal blood vessel growth.
Many children who develop stage II improve with no treatment and eventually develop normal vision. The disease resolves on its own without further progression.
VI 3.16c Stage III-Severely abnormal blood vessel growth.
The abnormal blood vessels grow toward the center of the eye instead of following their normal growth pattern along the surface of the retina. Some infants who develop stage III improve with no treatment and eventually develop normal vision.
VI 3.16d Stage IV-Partially detached retina.
Traction from the scar produced by bleeding, abnormal vessels pulls the retina away from the wall of the eye.
VI 3.16e Stage V-Completely detached retina and the end stage of the disease.
If the eye is left alone at this stage, the baby can have severe visual impairment and even blindness.
VI- 3.17- Strabismus
Disability Category: Visual Impairment
Definition
Strabismus involves deviation of the alignment of one eye in relation to the other (U.S. National Library of Medicine, 2004).
Explanation
Strabismus is due to the effects of a lack of coordination between the eyes. As a result, the eyes look in different directions and do not focus simultaneously on a single point. In most cases of strabismus in children, the cause is unknown. In more than half of these cases, the problem is present at or shortly after birth (congenital strabismus). In children, when the two eyes fail to focus on the same image, the brain may learn to ignore the input from one eye. If this is allowed to continue, the eye that the brain ignores will never see well. This loss of vision is called amblyopia, and it is frequently associated with strabismus.
Some other disorders associated with strabismus in children include: retinopathy of prematurity, retinoblastoma, traumatic brain injury, hemangioma near eye during infancy, apert syndrome, noonan syndrome, Prader-Willi syndrome, trisomy 18, congenital rubella, incontinentia pigmenti syndrome, cerebral palsy
A family history of strabismus is a risk factor. Farsightedness may be a contributing factor. In addition, any other disease causing visual loss may produce strabismus as a complication. Symptoms include eyes that appear crossed, eyes that do not align in the same direction, uncoordinated eye movements, double vision, and vision in only one eye with loss of depth perception (U.S. National Library of Medicine, 2004).
VI 3.17a-Constant Strabismus
When the eye turn occurs all of the time, it is called constant strabismus.
VI 3.17b-Duane’s Syndrome
Duane ‘s Syndrome is made up of three disorders:
Duane’s syndrome (type I) is made up of three parts: an inability to move an eye laterally away from the nose with widening of the eyes (palpebral fissure), retraction of the eye when attempting to look close or towards ones nose; and retraction of the eye.
Duane II where by the eye has trouble looking toward the nose (opposite to Duane’s I)
Duane III made up of a combination of I and II. A patient with Duane’s is likely to have an eye turn inwards at distance.
VI 3.17c Esotropia
Esotropia is the inward turning of the eyes. Esotropia is by far the most common type of strabismus, and is divided into two types: Paretic esotropia is due to paralysis of one or more of the nerves or muscles that turn the eye out and Non-Paretic is the most common type of strabismus seen in infants and children. Non-paretic esotropia can be further uncommon in childhood but accounts for most new cases of strabismus in adults.
VI 3.17d -Exotropia
Exotropia is the outward deviation (turn) of an eye. The deviation may occur while fixating (looking at) distance objects, near objects or both. Exotropia is much less common than esotropia. It tends to begin very gradually, and is initially only noted when the child is very tired, day dreaming or sick. With time, the out-turning becomes more evident during the day and may eventually become constant. Children with exotropia often squint or close one eye in the bright sunlight.
VI 3.17e- Hypertropia
Hypertropia is a vertical deviation of the eyes. This condition is much less common than the horizontal deviations that are seen in childhood. There are many causes for a vertical deviation. Sometimes there is a genetic tendency for one eye to be higher than the other. In other instances, children are born with eye muscles or nerves that do not work properly. In addition, trauma to the head, tumors in the brain or around the eye, certain diseases can all produce hypertropia. The first line of remediation is to treat the underlying problem, if one is present.
VI 3.17f-Intermittent Strabismus
When the eye turn occurs only some of the time, it is called intermittent strabismus or alternating strabismus.
VI – 3.18- Vision Loss due to Disease or Infection
Disability Category: Visual Impairment
Definition
Xeropthalmia or dry eye syndrome occurs when the tear glands produce fewer tears. The symptoms range from mild irritation and a sensation of something in the eye, to severe discomfort and sensitivity to light (U.S, National Library of Medicine, 2004).
Explanation
Dry eye syndrome often occurs in people who are otherwise healthy. It is more common with older age, because you produce fewer tears with age. In rare cases, it can be associated with rheumatoid arthritis, lupus erythematosis, and other similar diseases. It may also be caused by thermal or chemical burns.
In areas of the world where malnutrition is common, vitamin A deficiency is a common cause. This is rare in the United States (U.S, National Library of Medicine, 2004).
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