Purpose:
Cone photoreceptors, under certain illumination conditions, undergo fast stimulus-evoked changes in reflectance ("scintillation") at near infrared wavelengths [1]. While scintillation has been characterized for red stimuli (specifically 670 nm), other color stimuli have not been considered. The dependence of scintillation duration and pattern on stimulus color may provide additional insight into the function of cones, especially with regard to their spectral properties.
Methods:
Videos of the cone mosaic at 2.5 degrees eccentricity were acquired at 192 Hz over 2 s intervals using an adaptive optics retina camera. The imaging source was a near-infrared laser diode ( = 915 nm, Δ = 3 nm). Stimuli of various color, duration, and illuminance were delivered to the retina during the video acquisition. Registration of video images and inter-registration of videos allowed the comparison of scintillation for the same cone under different stimulus conditions.
Results:
Cones were found to scintillate at almost all stimulus wavelengths considered, but the number of cones that did and the duration and magnitude of the scintillation varied with the stimulus color. Some cones, for example, responded strongly to a red (670 nm) stimulus and weakly to a blue (<450 nm) stimulus, while others exhibited a reverse behavior (see Fig. 1).
Conclusions:
Cones scintillate differently depending on the stimulus color.[1] R. S. Jonnal et al., Opt. Express 15, pp. 16141-16160 (2007).
Figure 1. Reflectance of two representative cones as a function of time after delivery of red and blue stimuli.
Keywords: imaging/image analysis: non-clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors