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M. E. Mercer, M. L. Courage, R. J. Adams; Measuring Human Contrast Sensitivity: Does Varying the Test Distance Allow a More Complete Estimate of the Spatial CSF in Children. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1838. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Contrast sensitivity (CS) has emerged as a valuable tool for providing a comprehensive profile of human spatial vision as it provides good prediction of real-world visual functioning in both normal individuals and patients with a variety of ophthalmic, neuro-ophthalmic, and systemic disorders. In adults, a common strategy to increase the interpretative power of current CS tests is to test the patient at different test distances in order to expand the range of spatial frequencies, obtain repeated measurements, and/ or to create intermediate spatial frequencies, either of which allows one to plot a more extensive and accurate CSF. Given the emerging importance of testing CS in pediatric populations, we attempt here to determine whether this strategy is successful with young children.
Six groups of 20 4-to-9-year-old healthy children were evaluated binocularly in the same session with a card-based test of spatial contrast sensitivity (Adams et al, ARVO 05, 06). This test consists of sine-wave-gratings which at a distance of 80 cm, range in spatial frequency(SF) in 5 steps from 0.4 to 4.8 cy/deg and decrease in contrast from 33% (CS value = 3) to 0.4% (CS = 250). The test was then repeated at 160 cm and again at 320 cm, with SF doubling at each distance. For comparison, a group of adults (n = 20) was tested with the same procedure.
At 80 cm, all children and the adults completed testing at each SF and generated interpretable individual contrast sensitivity functions (CSF). Although few 4-and 5-year-olds completed testing at the longer test distances, data could be successfully combined across all distances to form individual composite CSFs for each 6- to-9-year-old and adult. Further analyses revealed that both the consistency and interpretability of these composite functions improved with age, particularly between ages 6 and 8.
At least with this technique which incorporates relatively small sine wave gratings (about 6 deg at 80 cm), the strategy of varying test distance to obtain more comprehensive estimates of contrast sensitivity is not feasible or reasonably accurate until approximately 7 years of age. Possible reasons for the poorer performance of younger children include attentional waning, the influence of stimulus size, or immaturities in more basic visual system properties such as retinal receptive field size or lateral inhibitory processes.
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