Dynamics of Visual Adaptation With Simultaneous Stimulation of Two Visual Pathways

Primates’ retinal ganglion cells in different visual pathways have been shown to adapt independently (Current Biology 22 (2012) 220–224). However, the manner in which adaptation occurs under simultaneous stimulation of two visual pathways has not yet been explored. In this study, the dynamics of color afterimages were measured while stimulating one or two visual pathway using a time-varying afterimage paradigm. The dynamics of adaptation was approximately equivalent among the three primary visual pathways, but adaptation was slower for simultaneous stimulation of two visual pathways compared to the stimulation of one visual pathway. In addition, we found that the speed of adaptation also depends upon which two pathways are combined. We developed a two-stage adaptation model, both with the same dynamics, to account for the results with simultaneous stimulation of two pathways.

Quantifying the effect of straylight on photopic contrast sensitivity

The visual performance of a reference group (RG) using diffuser filters was compared to a cataract-diagnosed group (CatG). Measurements of straylight (SL) parameter, photopic contrast sensitivity (CS), and visual acuity (VA) were carried out in both groups. Before the analysis, the performance of the instruments used for this purpose was tested. The RG was comprised of three healthy, young eyes (25-30 years old) while 59 subjects (aged 50-80 years old) with lens opacities were recruited for the CatG. Six diffuser conditions were tested in the RG. To discriminate between light scattering levels, SL measurements proved to be most sensitive, VA did not discriminate at all, while CS showed intermediate sensitivity. VA was not correlated with SL, while the correlation between CS and SL was significant (p<0.05) in both groups. Since the correlation in the RG was particularly strong, parameters of a linear regression model are presented. The behavior of CS as a function of SL was comparable to some extent between RG and CatG.