December 2008
Volume 8, Issue 17
Free
OSA Fall Vision Meeting Abstract  |   December 2008
Optimization of large tritan stimuli by correcting for individual variations in spectral sensitivity and macular pigment distribution
Author Affiliations
  • Neil R. A. Parry
    Vision Science Centre, Manchester Royal Eye Hospital & Faculty of Medicine, University of Manchester, UK
  • Anthony G. Robson
    Department of Electrophysiology, Moorfields Eye Hospital & Institute of Ophthalmology, London
Journal of Vision December 2008, Vol.8, 74. doi:10.1167/8.17.74
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      Neil R. A. Parry, Anthony G. Robson; Optimization of large tritan stimuli by correcting for individual variations in spectral sensitivity and macular pigment distribution. Journal of Vision 2008;8(17):74. doi: 10.1167/8.17.74.

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Abstract

Sensitivity to stimuli in the blue region of colour space is dramatically affected by macular pigment (MP) which varies greatly in terms of optical density and distribution between individuals. Psychophysical and electrophysiological studies that employ isoluminant colour stimuli need to account for these differences. If, for example, large (⪢2deg) nominally isoluminant fields are employed to investigate the koniocellular system, there is likely to be contamination of the response from luminance mechanisms. To circumvent this we have developed an adjustable subject-specific blue-yellow grating stimulus which comprises a series of concentric annular regions. Isoluminance can be specified for each annulus using minimum flicker. Tritanopic confusion lines can be specified according to a minimum distinct border criterion. The temporal frequency sensitivity to an 18deg diameter tritan 2c/deg grating is dramatically reduced when each of the 8 annuli is made isoluminant; the function is low-pass with a temporal resolution of 10Hz. If the central (1.2deg) isoluminance value is used for the whole stimulus, then the resolution limit increases to 20Hz. The onset visual evoked potential (VEP) the fully isoluminant stimulus shows a sharp negativity which differs from the offset response; this is a signature of chromatic activity. If isoluminance is set for the centre only, there are significant achromatic VEP components of opposite polarity. In conclusion, multiple annuli can be used to generate large isoluminant tritan stimuli that compensate for individual eccentricity-dependent changes in MP and spectral sensitivity. Such stimuli may be used to selectively probe koniocellular function at threshold and suprathreshold levels.

Parry, N. R. A. Robson, A. G. (2008). Optimization of large tritan stimuli by correcting for individual variations in spectral sensitivity and macular pigment distribution [Abstract]. Journal of Vision, 8(17):74, 74a, http://journalofvision.org/8/17/74/, doi:10.1167/8.17.74. [CrossRef]
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