August 2009
Volume 9, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2009
Test of senescent change in photopic spatial summation
Author Affiliations
  • Maka Malania
    Department of Ophthalmology & Vision Science, UC Davis, CA, USA
  • Frederic Devinck
    Experimental Psychology Laboratory, University of Rennes, France
  • Joseph L. Hardy
    Posit Science Corporation, CA, USA
  • Peter B. Delahunt
    Posit Science Corporation, CA, USA
  • Kenneth Knoblauch
    Departement Neurosciences Integratives, Institut Cellule Souche et Cerveau, France
  • John S. Werner
    Department of Ophthalmology & Vision Science, UC Davis, CA, USA
Journal of Vision August 2009, Vol.9, 1074. doi:10.1167/9.8.1074
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      Maka Malania, Frederic Devinck, Joseph L. Hardy, Peter B. Delahunt, Kenneth Knoblauch, John S. Werner; Test of senescent change in photopic spatial summation. Journal of Vision 2009;9(8):1074. doi: 10.1167/9.8.1074.

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

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Abstract

Previous research has demonstrated age-related increases in scotopic spatial summation area, correlated with age-related losses in rods and ganglion cells. Grating spatial summation is typically measured in terms of contrast threshold vs. area. As area increases, there is a decrease in contrast threshold up to a critical size, after which there is no further change in contrast threshold. We measured contrast detection thresholds for foveally presented stimuli over a range of sizes in groups of younger (age range 19–20 years) and older (age range 67–83 years) observers. To control for age-related changes in pupil area, the stimuli were presented in a Maxwellian-view optical system. A bite-bar and auxiliary optical system were used to maintain alignment of the pupil with respect to the optic axis of a 2x astronomical telescope. The stimulus was a 76 Troland, vertical, 5 cpd Gabor patch that was increased in area from 0.13 to 12.56 deg2. Threshold for each stimulus area was measured using a two-alternative forced-choice method combined with QUEST adaptive staircase procedure. The data demonstrated a reduction in threshold up to a critical area, and could be fitted with a bilinear function (having slopes of 0.5 and 0 on log-log coordinates) using a least-squares criterion to define spatial summation area (the inflection point of the two functions). Consistent with previous work, we find an age-related increase in contrast detection threshold. In contrast to scotopic conditions, we found that foveal, photopic summation area remains relatively intact with increases in age.

Malania, M. Devinck, F. Hardy, J. L. Delahunt, P. B. Knoblauch, K. Werner, J. S. (2009). Test of senescent change in photopic spatial summation [Abstract]. Journal of Vision, 9(8):1074, 1074a, http://journalofvision.org/9/8/1074/, doi:10.1167/9.8.1074. [CrossRef]
Footnotes
 This study was supported by National Institute on Aging (grant 04058) and Research to Prevent Blindness.
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