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

Rongwen Lu,Steven J Pittler,Xincheng Yao,Alexander M Levy,Qiuxiang Zhang

doi:10.1117/1.jbo.18.10.106013

Rongwen Lu, Steven J Pittler + Show 3 more

Open Access

https://doi.org/10.1117/1.jbo.18.10.106013

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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.

Highlights

The Stiles–Crawford effect (SCE) states that luminance efficiency is dependent on incident light direction relative to the eye axis.[1]
Our experimental results suggest that transient phototropic adaptation may quickly compensate for the loss of luminous efficiency in rods activated by oblique stimulation, which can explain the absence of the SCE in the rod system
Photoreceptor displacements were directly observed in near infrared (NIR) images (Video 1)

Summary

Introduction

The Stiles–Crawford effect (SCE) states that luminance efficiency is dependent on incident light direction relative to the eye axis.[1]. Our experimental results suggest that transient phototropic adaptation may quickly compensate for the loss of luminous efficiency in rods activated by oblique stimulation, which can explain the absence of the SCE in the rod system. The observed transient phototropic adaptation of retinal rods provides insight into the nature of vision and promises an intrinsic optical signal (IOS) biomarker. This would enable noninvasive, high-resolution assessment of rod function, which is known to be more vulnerable than cone function in aging and early age-related macular degeneration (AMD),[3,4] the most common cause of severe vision loss and legal blindness in adults over 50.3,5

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