September 2005
Volume 5, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   September 2005
Assessment of contrast sensitivity in infants and children with neurological impairment: A novel test using steady-state visual evoked potentials (ssVEPs)
Author Affiliations
  • J Calvert
    Yorkhill Division NHS Greater Glasgow, and Glasgow Caledonian University
  • M S. Bradnam
    Yorkhill Division NHS Greater Glasgow, and University of Glasgow
  • V Manahilov
    Glasgow Caledonian University
  • R Hamilton
    Yorkhill Division NHS Greater Glasgow, and University of Glasgow
  • D L. McCulloch
    Glasgow Caledonian University
  • A Mackay
    Yorkhill Division NHS Greater Glasgow, and University of Glasgow
  • G N. Dutton
    Yorkhill Division NHS Greater Glasgow, and Glasgow Caledonian University
Journal of Vision September 2005, Vol.5, 294. doi:10.1167/5.8.294
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      J Calvert, M S. Bradnam, V Manahilov, R Hamilton, D L. McCulloch, A Mackay, G N. Dutton; Assessment of contrast sensitivity in infants and children with neurological impairment: A novel test using steady-state visual evoked potentials (ssVEPs). Journal of Vision 2005;5(8):294. doi: 10.1167/5.8.294.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Children with neurological impairment often have visual dysfunction, including reduced contrast sensitivity. However, a lack of co-operation or developmental delay can make subjective testing slow and inaccurate. We have previously developed an automated objective visual acuity test using ssVEPs (Bradnam et al. 1994, 2001; Mackay, 2003, 2003a & b). In the present study we report a similar technique to objectively and rapidly assess contrast sensitivity thresholds.

Methods: The rationale for our technique is to acquire the most important information as quickly as possible, before the child loses co-operation. This is accomplished by real-time analysis of the individual's ssVEP, which determines the subsequent contrast levels to be presented. The stimulus presentation technique is based on an adaptive staircase method, usually used in psychophysical experiments. The starting point is a high contrast pattern, large initial steps in contrast allow the threshold region to be identified and subsequent smaller steps allow an accurate threshold to be established.

Results: The stimulus parameters and presentation protocol were optimized in order to obtain a rapid and accurate contrast threshold. The contrast range, contrast step size, stimulus presentation algorithm, spatial frequency, temporal frequency, scalp recording sites and length of recording time before accepting ‘no response’ were all investigated. As a result, it takes less than three minutes to estimate a contrast sensitivity threshold, with the threshold estimates being comparable to psychophysical estimates.

Conclusions: The use of ssVEPs, combined with sensitive objective signal detection and a staircase stimulus presentation is an effective strategy for determining contrast sensitivity.

Calvert, J. Bradnam, M. S. Manahilov, V. Hamilton, R. McCulloch, D. L. Mackay, A. Dutton, G. N. (2005). Assessment of contrast sensitivity in infants and children with neurological impairment: A novel test using steady-state visual evoked potentials (ssVEPs) [Abstract]. Journal of Vision, 5(8):294, 294a, http://journalofvision.org/5/8/294/, doi:10.1167/5.8.294. [CrossRef]
Footnotes
 This work is funded by the Scottish Executive Chief Scientist Office Grant Number: CZB/4/247
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