A New Interpretation of the Relative Central Scotoma for Blue Stimuli under Photopic Conditions
In an earlier paper a relative central scotoma for a blue stimulus as reported by Verriest and Israel and others was not found. The reason was thought to be a combination of luminance and target size differences between the experimenters, involving the phenomenon of summation.
A Goldmann perimeter identical to Verriest’s was used to examine six subjects on the Goldmann targets at three different target sizes and at the luminances used by Verriest.
Results show duplication of Verriest’s results when his method is followed, however this involves changing both size and maximum target luminance from colour to colour. When photometrically equated targets are used, and only target size is varied, from colour to colour, it becomes apparent that the foveal sensitivity for the blue target is no different than for the other targets, and in fact it is the parafoveal thresholds which are higher for the blue target. These results show an increase in sensitivity to a short wavelength stimulus with a dominant wavelength λD 454 nm, outside the fovea, the effect being maximal at the parafovea. This effect was absent in our study using a target of λD 474 nm, at a higher luminance value and a smaller target size.
KeywordsBackground Luminance High Luminance Dominant Wavelength Threshold Gradient Photopic Condition
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- Greve, E.L., Verduin, W.M. & Ledeboer, M. Two-colour threshold in static perimetry. Mod. Probl. Ophthal. 13: 113–118 (1974).Google Scholar
- Lakowski, R., Wright, W.D. & Oliver, K. A Goldmann perimeter with high luminance chromatic targets. Caned. J. Ophtlral. 12: 203–210 (1977).Google Scholar
- Nolte, W. Bestimmung achromatischer Schwellen für verschiedene Spectrallichter. Inaugural Dissertation, Universitätsaugenklinik Tübingen (1962).Google Scholar
- Ronchi, L. & Galassi, R. Absolute thresholds for monochromatic stimuli of various sizes and duration across the visual field. Doc. Ophthal. Proceedings Series 14: 423–426 (1976).Google Scholar
- Sloan, L.L. Instruments and techniques for the clinical testing of light sense. III. An apparatus for studying regional differences in light sense. Arch. of Ophthal. 22: 233–251 (1939).Google Scholar
- Sloan, L.L. The threshold gradients of the rods and the cones; In the dark-adapted and in the partially light-adapted eye. Ana J. Ophthal. 33: 1077–1088 (1950).Google Scholar
- Verriest, G. & Israel, A. Application due perimetre statique de Goldmann au releve topographique des senils differentiels de luminance pour petits objects colores pro-jectes sur un fond blanc. Vision Res. 5: 151–174, 341–359 (1965).Google Scholar
- Wentworth H.A. A quantitative study of achromatic and chromatic sensitivity from center to periphery of the visual field Psychol Monogr 40:(3)Nr 183 (Dissertation) (1930).Google Scholar