Developmental Disabilities

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Techniques for Infants and Toddlers with Visual Impairment - Of Visual Impairment

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by Alycyn Ferrell and Sharon A. Raver

It is difficult to delineate accurately the causes of visual impairment in infancy. There are now national registers of individuals with visual impairments, and in states where mandatory reporting laws are in effect, the states often have little enforcement. Consequently, etiology estimates are based either on small samples from a limited graphic area on national counts with recognized unreliable methods of data collection.

Nonetheless, some generalizations can be made. In general, visual impairment in infancy has three causes, inheritance, prenatal infection or injury, and peri-or postnatal insult. Ferrell (1987) reported preliminary data on a national survey of categorical programs serving 1,671 children with visual impairment younger than age 5. The leading cause of visual impairment in this sample were cortical blindness (21%); retinopathy of prematurity (20%); optic nerve hypoplasia (7%); congenital cataracts (6%); and Leber’s amaurosis, alinism, and optic atrophy (5%). A study conducted in the New York City metropolitan area by the Visually Impaired Infants Research Consortium (VIIRC) (Ferrell et. Al., in press) found a similar pattern. This study reports that of the 82 children that were served, the leading causes of visual impairments are retinopathy of prematurity (23.25%), cortical blindness (13.4%), and Leber’s amaurosis (12.2%).

Although figures may vary between regions and states, these two studies, regardless of their limitations, permit inferences about the current population of visually impaired infants.

Retinopathy of prematurity. A large proportion of infants are visually impaired as a result of retinopathy of prematurity, a pathology that 5 years ago was predicted to disappear (Hatfield, 1975). Instead, the incidence of this disease has risen sharply with increased survival rate of extremely low birth weight infants (Phelps, 1981; Silverman, 1982). Retinopathy of prematurity (ROP) is an eye condition associated with prematurity which can lead to detachment of the retina and visual impairment or blindness. Once known as retrolental fibroplasia and thought to be caused by excessive oxygen administration after birth, medical scientists have yet to determine ROP’s exact cause. At present, it appears to be associated more with low birth weight than any other factor (Flynn, 1987). However, there is also limited evidence that ROP may be influenced by intensity of light exposure in neonatal hospital units (Glass et al, 1985), the number of hours the infant requires ventilator assistance (Hammer et. al., 1986), multiple spells of apnea and/or bradycardia (Flynn, 1987), and the need for blood transfusions (Hammer et. al., 1986). This condition creates a very difficult dilemma for medical professionals because, at present, ROP seems to be an inevitable condition of prematurity for some infants.

Cortical blindness. The large proportion of children with cortical blindness may reflect the difficulty in diagnosing visual abilities in infants, or more likely reflects a catch-all term applied to infants with severe brain insult. Cortical blindness is defined as a disturbance of the visual cortex in the absence of any other known pathology. Seventy-eight percent of children described as having cortical blindness in Ferrell’s (1987) study were also reported to have one or more addition handicapping conditions; all of the children with cortical blindness in the VIIRC study (Ferrell et. al., in press) are also multiply handicapped. This appears to support the possibility that cortical blindness is being used to describe any severe brain insult that results in blindness.

Other causes. The remaining causes of visual impairment suggest either hereditary factors such as albinism, or a disturbance in the development of the eye in utero affecting either the lens (e.g., cataracts) or the retina and associated structures (e.g., optic nerve hypoplasia, Leber’s amaurosis). As Hatfield (1975) predicted, infection is no longer a major cause of eye pathology in infants in the United States.

None of the leading causes of visual impairment appear to produce a predictable developmental pattern in infants. Retinopathy of prematurity (ROP) may affect only a small portion of the retina, or it may lead to retinal detachment and total blindness. Other retinal disorders differ according to where the lesions occur. Infants with the same visual diagnosis, born on the same day, and in the same hospital will, more likely than not, have completely different patterns of visual functioning and overall development.

The variability in the etiology of visual impairments, the vicissitudes of different environments, and the difficulty of identifying and referring infants for early intervention services all work together to make it difficult to predict the developmental outcome of any young child.

In 1989, Dr. Turben received funding that enabled the Cleveland Sight Center to initiate the first large-scale, family-centered Children's Services Program in Cleveland, Ohio. Dr. Turben worked for Lake County Early Intervention Collaborative Group in 1988-89 as the consultant who prepared the County Needs Assessment and assisted the collaborative in the preparation of the 1988-89 Lake County Early Intervention Collaborative Plan, which launched family collaboratives as a network of families with children who had disabilities.
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