Measurements were made of the change of threshold during and after exposure to scotopically and photopically equivalent spectral lights using a constant small b wave in the frog’s electroretinogram as criterion.
After exposure to spectral lights of equal photopic luminance, the rod branch of the dark-adaptation curve occurs earlier after orange than after blue adaptation while the cone branches are the same. After exposure to lights of equal scotopic luminance, during the cone branch of the dark adaptation curve the threshold is higher after orange than after blue adaptation while the rod branches are the same.
Incremental thresholds have been determined for test lights of various wavelengths at stepwise increased levels of adaptive illumination with orange and blue lights of equal scotopic efficiency. With blue adaptation the loss of blue sensitivity is as large as the loss of orange sensitivity with orange adaptation whereas the effect of blue adaptation on orange sensitivity is much smaller than the loss of blue sensitivity with orange adaptation. It is concluded that blue light mainly depressed the rods while orange light depresses rods and cones in more nearly equal proportions. No test light was found which would change the increment threshold equally with orange and blue adaptation.
The use of blue glasses is recommended to preserve a high cone sensitivity during and after exposure to bright lights of equal scotopic efficiency.
© 1961 Optical Society of AmericaFull Article | PDF Article
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