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Xincheng Yao, Rongwen Lu, Benquan Wang, Qiuxiang Zhang; Spatiotemporal mapping of retinal phototropic response evoked by oblique light stimulation. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6190.
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This study was designed to map transient phototropic response in the retina evoked by oblique visible light stimuli, and to compare the orientation dependent dynamics in rod and cone photoreceptors.
Both frog (Rana pipiens) and mouse (Mus musculus) retinas were used to demonstrate the transient phototropic response in the retina. Animal handling was approved by the Institutional Animal Care and Use Committee of the University of Alabama at Birmingham. The imaging system consisted of two light sources: a near infrared (800-1000 nm) light for retinal imaging and a visible (450-650 nm) light for retinal stimulation. Visible light flashes with oblique incident angle were used to test the effect of the stimulus direction. The duration of each visible flash was 5 ms. Near infrared images of the retina were acquired at 200 frames/s. Localized retinal movements were calculated at cellular resolution. Rod and cone photoreceptor dynamics were quantitatively compared.
High-spatial (micrometer) and high-temporal (millisecond) resolution NIR imaging revealed 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. In contrast, such directional movement was negligible in retinal cones.
Rod-dominant transient phototropic response in frog and mouse retinas was observed. Such transient phototropic response might compensate for the loss of illumination efficiency under oblique stimulation in the rod system, which can explain the absence of the Stiles-Crawford effect in rod system. Moreover, the observed transient rod movement promises a characteristic biomarker to enable selective mapping of retinal rod dysfunction, which is valuable for early detection of age-related macular degeneration and other eye diseases.
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