Abstract
Abstract: :
Purpose:A simple psychophysical method was developed for deriving tritanopic pairs using heterochromatic flicker photometry under different adaptation conditions. It relies on the lack of S cone input to photometric matches. Methods:The red and blue guns of a display are modulated with fixed relative modulation depths, in counterphase with the green gun which is fixed in amplitude. Yoked red and blue amplitudes are adjusted by an observer to reach a flicker null. The red/blue ratio is changed and the null repeated. With different mean chromaticities, red and blue modulations at the flicker null form linear relations of different slope (photometric linearity) depending on the background, indicating differential adaptation of M and L cones. Results:Under three different adaptation conditions, the three linear relations derived for trichromats yield a tritan pair at their intersection. For all observers, tritan pairs obtained using this technique were similar to tritanopic confusion lines derived using other methods. Consistent with no S–cone involvement, data from dichromats showed similar slopes under different adaptation conditions. Physiological measurements showed behavior in macaque MC cells to resemble the psychophysical data. Conclusions: This technique provides a rapid and reliable method to estimate tritanopic pairs which makes no assumptions about cone fundamentals. It is straightforward to use with naïve observers and can be used with other photometric methods.
Keywords: color vision • photoreceptors: visual performance • retina: proximal (bipolar, amacrine, and ganglion cells)