Abstract
Unique green (UG) wavelength settings are typically more variable than other unique hue wavelengths. This increased variance suggests that there are several factors contributing to UG settings. A number of studies have investigated whether these settings are best fit by a uni- or bi-modal distribution, whether there are gender differences in average settings, and whether individual differences can be accounted for by variation in retinal melanin concentrations. This investigation primarily focused on the potential role of macular pigment density in the perception of UG, but iris lightness and colour were also measured to investigate previous claims of a relationship between these factors and both UG and macular pigment density. We used a two-channel Wright colorimeter to obtain UG and macular pigment optical density (MPOD) measurements from 28 males and 30 females. We found that MPOD has a significant positive relationship with unique green values (r = 0.31, p (one-tailed) < 0.01), with higher densities predicting longer wavelengths of unique green. Iris lightness did not predict unique green independently, and whilst it was found in a multiple regression that both iris lightness and MPOD significantly predict unique green (F(1,55) = 4.623, p = 0.014), it was also shown that iris lightness did not significantly contribute to the model (? = -0.213, p = 0.09). The distributions of both UG and MPOD were well-fitted by uni-modal normal distributions. MPOD settings also exhibited a near-significant relationship with gender suggesting that gender may have an effect on UG settings as well.
Meeting abstract presented at OSA Fall Vision 2012