Symbol Discrimination Speed in Children With Visual Impairments

Abstract

Citation: Barsingerhorn AD, Boonstra FN, Goossens J. Symbol discrimination speed in children with visual impairments. Invest Ophthalmol Vis Sci. 2018;59:3963-3972. https://doi.org/ 10.1167/iovs.17-23167 PURPOSE. We measured visual acuity and visual discrimination speed simultaneously in children with visual impairments to determine whether they are slower than children with normal vision.METHODS. Five-to twelve-year-old children with visual impairments due to ocular dysfunction (VI o ; n ¼ 30) or cerebral visual impairment (CVI; n ¼ 17) performed a speed-acuity test in which they indicated the orientation of Landolt-C symbols as quickly and accurately as possible. The reaction times for symbols ranging between À0.3 and 1.2 logMAR relative to acuity threshold were compared with normative data. To test whether children were already slow in merely detecting symbols, we also compared their reaction times on a simple visual detection task (VDT) to normative data. An auditory detection task (ADT) was used to probe for other, more general deficits. RESULTS.Of the children with visual impairments, 88% had abnormally long reaction times in the speed-acuity test. This deficit was partly explained by their reduced acuity, but 40% still needed more time to discriminate acuity-matched optotypes. Children responded late in the VDT too, especially those with CVI, but this impairment could not fully account for their slow symbol discrimination. In children with CVI, reaction times in the ADT were affected as much as those in the VDT, suggesting more general sensorimotor problems in CVI.CONCLUSIONS. The speed-acuity test offers additional insight in visual impairment. Children with VI o and CVI are abnormally slow in discerning foveal details. Magnification of materials is often insufficient to compensate for this deficit, partly because stimulus detection is already hampered.

The worse eye revisited: Evaluating the impact of asymmetric peripheral vision loss on everyday function

“…It did, however, cause response times to be significantly slower (by over 200%, in the bilateral-symmetric case), and compelled participants to make substantially more head-and eye-movements. These findings echo a recent report by Barsingerhorn and colleagues 64 , who observed that children with ocular dysfunction were slower at performing a simple spatial judgment (landolt-C orientation-identification) than their normal-sighted peers, even after the stimuli were matched in size for relative acuity. Taken together, such findings suggest that when characterizing vision loss, it may be prudent to move beyond simple functional measures of accuracy.…”

Saccade latencies during a preferential looking task and objective scoring of grating acuity in children with and without visual impairments

“…The results revealed that 40% of the children with visual impairments needed more time to discern optotypes (Barsingerhorn et al. 2018b) than one might expect from their reduced visual acuity alone.…”

“…), and they need more time for the discrimination of optotypes (Barsingerhorn et al. 2018b) compared to children with normal vision.…”

“…Recent studies on the time children need to discriminate optotypes revealed that the button‐press reaction times increased as the optotypes approached the discrimination threshold in children with normal vision and in children with visual impairments (Barsingerhorn et al. ,b). In addition, because in these studies the optotypes ranged from below visual acuity to well above threshold, the reaction times could be corrected for reduced visual acuity.…”

“…2018a) and in children with visual impairments (Barsingerhorn et al. 2018b). The children who participated in the present study also participated in those previous studies.…”