Vision
Loss and Blindness
346 - Psychology of Exceptional Children
(4-21-15)
Vision
eye: receptor organ for visual stimuli
cornea: external covering
lens: focuses light
pupil: opening through which light enter the eye
iris: mechanism adjusting the amount of light entering the eye
retina: light sensitive cells (considered part of central nervous system)
rods: monochromatic vision, less distinct vision
cones: color vision, more distinct vision
optic nerve
optic chiasm
optic tract
lateral geniculate nucleus (body): LGB
layer IV of the visual cortex (striate cortex) in the Occipital Lobe: pattern analysis
secondary pathways (tectopulvinar pathway: detection and orientation of visual stimuli: visual system of fish, amphibians, and reptiles)
Blindness
Legal: Visual Acuity & Field of Vision
Educational: Vision as an Avenue for Learning
Partial Sight (low vision)
Educational: Level and Extent of Support Services Needed
Profound, Severe, Moderate: task difficulty, time, and accuracy
Classification of vision problems:
Refraction eye problems: most common
Muscle disorders
Receptive eye problems
Optic atrophy
Retinitis pigmentosa (RP)
Retinal Detachment
Retrolental fibroplasia (RLF): excessive O2 leads to scaring behind lensesColor discrimination
Prevalence of Visual Differences
approximately 20% of general population experience visual problems: most of these deficits can be corrected: glasses, contact lenses, surgery
approximately 5% of school age children have a serious eye disorder
Etiology
Hereditary disorders: a number of genetic disorders can cause vision loss
Acquired disorders:
Congenital
Constitutional
Consequences--age of onset
Congenital vs. Acquired
loss after age 5: retention of visual frame of reference
Basic perceptual abilities in nonvisual modalities: unremarkable
"sensory compensation"--popular belief that blindness yields an improvement in the basic acuity of other senses, especially hearing and touch, no consistent evidence supports this: "basic sensory discriminative abilities are much the same in blind, partially sighted, and sighted samples." (Warren, 1994, p. 29)
Intelligence
When appropriately evaluated, intelligence appears relatively normally distributed in blind children; however, some of the etiologies associated with vision loss are also risk factors for intellectual limitations (brain injury from prenatal factors or traumatic injury)
general knowledge of the world
dreaming and congenital blindness
Those blind since birth or early childhood report no visual imagery in dreams (Hurovitz, Dunn, Domhoff, & Fiss, 1999)
REM activity is usually absent in congenitally blind individuals, but the frontal lobe activation usually associated with REM activity in normally sighted individuals is seen (Kirtley, 1975)
Perceptual-Motor Developmentspatial concepts
"Empirical studies on congenitally blind people have frequently reported that mental imagery does not depend upon visual perception." (Cornoldi & Vecchi, 2000, p. 147)
"In sum, results indicate that blind people are able to use mental representations to analyze visuospatial patterns, although their performance could be less effective in complex tasks and the process could take longer." (Cornoldi & Vecchi, 2000, p. 148)
Gomulicki (1961) presented extensive data on a sample of British children that lead itself to a similar conclusion. He did point out the cost of this development--allocation of general intellectual resources: "This suggests that a prolonged effort of the intellect is part of the cost to the blind of a degree of perceptual skill that for the sighted is a relatively effortless product of maturation. While the young blind child is still trying to master basic perceptual skills, the sighted child of equal age and intelligence is already able to begin using these skills for more complex learning."
Vision provides a good basis for spatial representation because of several features (Ungar ): 1) relatively simultaneous perception of a large spatial field. Although "point of foveations" is limited, peripheral vision allows some cuing of nearby objects. Ungar uses illustration that haptic exploration is like foveations without peripheral vision--the position of objects not being attended to must be maintained in memory and without available cues to direction. 2) vision is more precise in accuracy of location (distance and direction) and identification.
Ungar's review suggests that individual differences in spatial performance by blind participants reflect in behavioral or coding "strategies used to acquire and organize spatial information." He suggests that the lack of visual experience leads to subjects tending to use certain strategies and that this accounts for the group differences observed (rather than any absolute disability). He follows up with educational recommendations.
motor and locomotion
"The evidence clearly supports the conclusion that children with visual impairments are at risk for poor physical fitness." (Warren, 1994, p. 51); Warren goes on to discuss the relationships involved: "Investigators agree that poor fitness is not a necessary consequence of visual impairment. . . . The opportunities that the child has for engaging in physical activities, and the encouragements that they receive to do so, are the keys." (p. 51).
stereotypic behaviors or mannerisms: repetitive movements of parts of the body (eye rubbing, head turning, hand gestures) and larger body movements (rocking, swaying). Warren suggests that the term "blindism" is a misnomer because these self-stimulatory responses are not qualitatively different that those seen in some autistic children or (at a low frequency) in most children. At high rates stereotypic behaviors may interfere with normal social interaction and may interfere with attention. Stereotypic behavior usually decreases with age.
Mannerisms can be contrasted with other nonverbal behavior--gestures, posture, fidgeting
Speech and LanguageInfants with visual impairments beginning speaking at about the same time as sighted infants (Warren, 1994)
verbalism: the reported tendency of deaf children to use words of which they do not have firsthand sensory experience (Warren, 1994, p. 139), term was introduced by Cutsforth in a 1932 publication. Psychoanalytic writers referred to a similar language behavior as parroting (Burlingham, 1961, p. 137)--that the blind child's speech was "less firmly connected to his sensory experience." Warren (1994) argues that, "it is clearly not valid simply to assume that the use of visual words is indicative of 'low thinking' on the part of blind children," ( 141) and maintains that visually related vocabulary should not be discouraged (p. 142).
Educational AchievementAcademic progress of children who are blind or show significant vision loss tends to lag behind their sighted peers
This is commonly viewed as reflecting the cumulative impact of reduced experiences, but may be exacerbated by oversimplified verbal communication from caretakers (McConachie & Moore, 1993)
Social Developmentbody language, nonverbal communication, incongruent expressions
"Isolation seems to be a function of visual impairment, but loneliness is more often connected with cognitive and emotional factors." (Karlsson, 1988, p. 488). Adolescents with vision impairment tend to small circles of friendship and fewer dates than their fully sighted companions, and reported more feelings of loneliness and difficulties making friends (Huurre & Aro, 1998).
Adjustment
Visual impairment does not, of itself, increase the risk for behavior problems (Warren, 1994).
Depression, distress, and difficulties in parental relationships were no greater in visually impaired adolescents than in their sighted peers in a study in Finland (Huurre Aro, 1998), these authors did find that self-esteem, school achievement, and social skills were lower in girls with visual impairments than in girls in the control sample.
Vision loss after the individual has developed a self-image of being sighted may cause greater risk for psychosocial adjustment (Gherghel, 2003; Ulsin, Jacobson, & Rand, 1991). Hatlen (2002) suggests that, "for the adventitiously blinded adult, the major issues of blindness would probably be psychological, while for the congenitally blind child, most issues would be social. The child, who knows no other condition than blindness, may not have any psychological reaction to being blind. On the other hand, every social skill that is incidentally, casually learned through vision will need to be taught to blind children."
Mobility
Independence of mobility is one of the single most important challenges affecting the quality of life, education, personal development, and vocational opportunities of children with vision loss.
Inclusion, Acceptance, Politics
National Federation of the Blind
Braille
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