Dynamic near-infrared imaging reveals transient phototropic change in retinal rod photoreceptors

Abstract

Abstract. Stiles-Crawford effect (SCE) is exclusively observed in cone photoreceptors, but why the SCE is absent in rod photoreceptors is still a mystery. In this study, we employed dynamic near infrared light imaging to monitor photoreceptor kinetics in freshly isolated frog and mouse retinas stimulated by oblique visible light flashes. It was observed that retinal rods could rapidly (onset: ∼10 ms for frog and 5 ms for mouse; time-to-peak: ∼200 ms for frog and 30 ms for mouse) shift toward the direction of the visible light, which might quickly compensate for the loss of luminous efficiency due to oblique illumination. In contrast, such directional movement was negligible in retinal cones. Moreover, transient rod phototropism could contribute to characteristic intrinsic optical signal (IOS). We anticipate that further study of the transient rod phototropism may not only provide insight into better understanding of the nature of vision but also promise an IOS biomarker for functional mapping of rod physiology at high resolution. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Stimulus-evoked outer segment changes occur before the hyperpolarization of retinal photoreceptors

“…Transient retinal phototropism (TRP) has been observed in both amphibian (frog) and mammalian (mouse) retinas illuminated by oblique visible light [1]. High-resolution microscopy revealed that the TRP is dominated by rod photoreceptors.…”

“…As the ROS movement represents a morphological change in the retina, it is logical to hypothesize that the phototropic response of ROSs is a key component of the light-scattering signal [9], i.e., TRP may also originate from the ROSs. Our previous studies showed that the onset time of the intrinsic optical signal (IOS) precedes the onset time of the electroretinographic (ERG) a-wave, which reflects the hyperpolarization of photoreceptor outer segments (OS) [10,11], and the rod dominant phototropism was suggested to be a primary contributor to the IOS [1,12]. Therefore, we further hypothesized that the onset of TRP occurs earlier than cell hyperpolarization in the phototransduction cascade.…”

In vivooptical coherence tomography of stimulus-evoked intrinsic optical signals in mouse retinas

“…11 These studies also revealed that photoreceptor IOSs had a rapid time course (<4 ms after onset of the light stimulus). 13,28 Transient retinal phototropism was reported to be one factor that generates photoreceptor IOSs, [31][32][33] but the IOS physiological source has not been accurately determined yet. Before pursuing clinical applications, it is necessary to establish the relationship between IOS distortions and eye diseases.…”

Stimulus-evoked outer segment changes in rod photoreceptors

“…9 Recently, oblique light stimulation evoked transient retinal phototropism (TRP) has been detected in amphibian (frog) and mammalian (mouse) retinas. 10 High-resolution microscopy of freshly isolated retinas indicated that TRP is predominated by rod photoreceptors. 10 We speculate that the rod-dominated TRP may provide a quick compensation for the light inefficiency of oblique illumination, and the time course of the observed TRP can be too short to be detectable by the psychophysical methods used for traditional SCE studies.…”