Visual Impairments Determining Eligibility for Social Security Benefits (2002) / Chapter Skim
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4. Assessment of Vision in Infants and Children
4. Assessment of Vision in Infants and Children
Pages 199-230
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From page 199... ...
The testing of children's vision is important to SSA because Title XVT of the Social Security Act provides for SST benefits for children with disabilities, and acceptable methods must be specified for determining disability in this population. This chapter reviews the major issues in testing infants' and children's visual acuity, fields, and contrast sensitivity and offers some recommendations for testing to ensure fair evaluation of their visual abilities.
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From page 200... ...
First, the results of visual assessment must be compared with normative data from infants of the same age, tested with the same assessment tool. Comparing results to norms based on data from adults or older children or to infants tested with a different procedure can lead to a misdiagnosis of visual impairment.
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From page 201... ...
with a marked limitation being a score that is 22 but <3 standard deviations below the norm for the test, and an extreme limitation being a score that is 23 standard deviations below the norm. What is implied but not specifically stated in these criteria is that the norm is specific to the age of the child.
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From page 202... ...
As with infants, the changing visual and cognitive status of the young child makes it especially important that visual assessment results of preschool children be compared with results from normal children of the same age tested with the same technique. This is recognized by the Social Security Administration regulations, as described above.
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From page 203... ...
Adults and School-Age Children Who Cannot Perform Standard Tests of Visual Function Some adults and school-age children cannot be tested using standard adult tests of visual function, due to limitations related to language, physical, or cognitive abilities. For these individuals, useful information about their visual capabilities may be obtained by assessing them with tests designed for younger children or infants.
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From page 204... ...
Visual acuity is the one aspect of visual function for which there are well-established, validated tools for assessment of infants and young children. Furthermore, age-normative data are available for most of these assessment tools.
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From page 205... ...
Normative data are available for VEP acuity for infants between birth and age ~ year (McCulloch et al., 1999; Norcia & Tyler, 1985~. However, use of the VEP for measurement of visual acuity in individual infants has been limited to a relatively small number of clinical sites, undoubtedly due to the expense of the equipment and the technical expertise required to conduct the test.
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From page 206... ...
Thus, visual acuity can be measured by observing an infant's eye movement responses to black and white gratings paired with a gray stimulus matched to the spaceaveraged luminance of the gratings. The version of the procedure that is commercially available and is most widely used to measure visual acuity in infants is the acuity card procedure (Teller et al., 1986~.
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From page 207... ...
Normative data have been published for the acuity card procedure for both binocular and monocular testing of infants between birth and ~ year, as well for young children up to 3 to 4 years of age (Courage & Adams, 1990; Mayer et al., 1995; Salomao & Ventura, 1995~. The acuity card procedure has been used successfully in a wide range of clinical settings to assess grating acuity in visually at-risk infants.
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From page 208... ...
with modifications in the positioning of the cards, the procedure can be used to test infants with oculomotor abnormalities, such as nystagmus; and (~) data are available on the distribution of acuity results in normal infants of different ages, making it possible to interpret an infant's visual acuity score in terms of number of standard deviations below normal, as suggested in the current SSA regulations.
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From page 209... ...
Thus, infants with grating acuity in the normal or near normal range at ~ year are likely to have normal recognition acuity at 5.5 years, and those with acuity too poor to be measured with acuity cards will continue to have impaired vision at age 5.5 years. However, the grating acuity score obtained with the acuity cards at age ~ year cannot be used to predict a child's recognition acuity score upon reaching kindergarten age.
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From page 210... ...
Two other tests that use left-right symmetric letters, with a logMAR progression in letter size, are the Glasgow acuity cards (McGraw & Winn, 1993) and the B VAT (Mentor, Tnc.)
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From page 211... ...
Normative data for children between ~ and 4 years of age have been published by several groups (Heersema & van Hof-van Duin, 1990; Courage & Adams, 1990; Mayer et al., 1995; Salomao & Ventura, 1995) , making it possible to interpret a child's visual acuity score in terms of number of standard deviations below normal, as suggested in the current SSA regulations.
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From page 212... ...
, who were at risk for visual deficits due to severe retinopathy of prematurity (Cryotherapy for Retinopathy of Prematurity Cooperative Group, 1996~. After excluding 56 cryotherapy-treated eyes and 85 control eyes judged to have no quantifiable pattern vision, an ETDRS acuity score was obtained for Il6/177 (65.5 percent)
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From page 213... ...
were able to complete near acuity testing of each eye. Among very low birthweight children with severe retinopathy of prematurity who were tested at age 10 years in the CRYO-ROP study, ETDRS monocular near acuity scores were obtained in 144 (91.7 percent)
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From page 214... ...
Alternatively, for the 3-year-old, it may be necessary to use familiar shapes rather than letters on the acuity chart, and to reduce the number of symbols that the child must identify during testing. Regardless of whether the preschool-age child is tested with a standard adult test, such as the ETDRS chart or Bailey-Lovie chart, or with a test designed for preschoolers, such as the Lea symbols test, it is important to compare the child's results with the results of other children of the same age tested with the same method, rather than with the results of adults, since visual acuity typically does not reach adult levels prior to a child's entering elementary school (Atkinson et al., 1988; Dowdeswell et al., 1995~.
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From page 215... ...
This longitudinal change in visual acuity supports SSA's use of "number of standard deviations below age norm" in the disability determination process, as well as its requirement for periodic reassessment of the visual status of children who meet disability requirements. The fact that the longitudinal change in visual acuity is not linear, however, indicates that another SSA regulation the one that recommends comparing the visual acuity results of a potentially visually disabled child with results of normal children of half that child's age is inappropriate.
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From page 216... ...
There is a long history of using perimetry and visual field testing to evaluate the status of peripheral vision in adults in both clinical and research settings. Automated static perimetry is available in the offices of most eye care practitioners, and the limitations of restricted visual field extent and of nonseeing areas within the visual field have been widely studied.
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From page 217... ...
An observer hidden behind a black curtain watches to make sure that the infant is looking centrally at the beginning of each trial and indicates when the infant makes an eye movement away from center. The location of the peripheral white sphere when the infant makes an eye movement toward that target is used as an estimate of visual field extent along that perimeter arm.
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From page 218... ...
The major disadvantage of static perimetry is that strategies have not yet been devised for eliciting enough trials from an individual infant to quantify that infant's visual field status (Maurer & Lewis, 1991~. Pe rim e try in Visua//yAt-Risk Infants White sphere kinetic perimetry has been used in a number of studies of visually at-risk infants, including those with retinopathy of
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From page 219... ...
. Assessment in Preschool-Age Children The only quantitative method that has been widely used to assess visual field extent in preschool children who cannot cooperate for perimetry using stanclarcl aclult procedures is the white sphere kinetic perimetry technique that was developed for use with infants (Mohn & van Hof-van Duin, 1986)
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From page 220... ...
By permitting the tester to use the child's eye movement responses, rather than buzzer-pressing, to indicate detection of a peripheral stimulus, successful measurement of visual field extent using Goldmann perimetry has been accomplished in both normal and visually at-risk children between 3 and 5 years of age (Cummings et al., 1988; Mayer et al., 1991; Quinn et al., 1991; de Souza et al., 2000~. Although normative Goldmann perimetry data for preschool children have not been published, data from Quinn et al.
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From page 221... ...
Goldmann perimetry has been useful in measurement of visual field extent in school-age children with a variety of visual disorders, including severe retinopathy of prematurity with or without peripheral retinal ablation (Takayama et al., 1991; Quinn, Miller, et al., 1996; Cryotherapy for Retinopathy of Prematurity Cooperative Group, 200Ib) , aphakia following removal of unilateral or bilateral dense.
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From page 222... ...
(1999) found that age differences in sensitivity to peripheral stimuli were related more to differences in attentiveness than to sensory differences across ages, their studies highlight the importance of comparing automated static perimetry results from at-risk children with data from normal children of the same age tested with the same equipment and procedure.
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From page 223... ...
Morales and Brown found that a training session of approximately one minute was all that was needed for children to be able to complete the ultra-short Octopus TOP-32 program. in summary, although it is possible to test many young school-age children with automated static perimetry, care must be taken to ensure that the child understands and can perform the task prior to beginning the actual measurement of sensitivity at different locations within the visual field.
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From page 224... ...
Recommendations Tf possible, visual fields of children should be assessed with the method that is recommended for adults, i.e., automated static perimetry. For children who are too young to be tested with standard adult perimetry procedures, there are no widely available, quantitative perimetry techniques and therefore no standardized methods for evaluating disability related to restricted visual fields.
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From page 225... ...
However, there are no widely available, normed and validated tools for assessment of contrast sensitivity in infants or preschool-age children. While visual acuity provides a measure of the finest detail that an individual can resolve, results of contrast sensitivity testing provide information on the individual's ability to detect patterns of all sizes, and thus they provide a more complete description of an individual's visual environment than can be obtained from a visual acuity score.
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From page 226... ...
and infants with Down syndrome (Courage et al., 1997) have been tested successfully with an acuity card type of contrast sensitivity test and normative data are available for infants (Adams & Courage, 1996)
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From page 227... ...
For children younger than age 3 years, it may be possible to measure contrast sensitivity with an acuity card procedure, similar to that used to measure grating acuity in this age range. initial data obtained from normal 2- and 3-year-olds (Adams & Courage, 1993)
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From page 228... ...
Unlike the Vistech chart, which measures contrast sensitivity for individual spatial frequencies, the Pelli-Robson charts provide a single contrast sensitivity value based on multi-spatial-frequency letter targets. Using the Pelli-Robson charts, Fitzgerald et al.
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From page 229... ...
For children who are too young to be tested with standard adult contrast sensitivity measures, there are no widely available techniques for assessment of contrast sensitivity and therefore no standardized methods for evaluating disability related to deficits in contrast sensitivity.
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From page 230... ...
Another area in which research is needed concerns the effect of contrast sensitivity deficits on activities of daily living and quality of life in children. This investigation should include children old enough to be tested with adult contrast sensitivity procedures, as well as children and adults whose cognitive development is not sufficient to allow them to be evaluated with adult procedures.
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