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Xincheng Yao, Xiaohui Zhao, Damber Thapa, Benquan Wang, Yiming Lu; Time-lapse near infrared microscopy reveals stimulus-evoked photoreceptor outer segment shrinkage and shift. Invest. Ophthalmol. Vis. Sci. 2016;57(12):582. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
This study is to investigate biophysical mechanism of transient retinal phototropism (TRP). Oblique light stimulation evoked TRP has been observed in mouse and frog retinas. High resolution microscopy of freshly isolated retinas indicated that the TRP is predominated by rod photoreceptors. Comparative confocal microscopy and optical coherence tomography (OCT) revealed photoreceptor outer segment (OS) movement. However, biophysical mechanism of rod OS movement is still unknown.
Frog retinal slices, which open a cross section of the photoreceptor and inner retinal layers, were used to test the effect of light stimulation on rod OS. High-speed and high-resolution near infrared (NIR) light microscopy was employed to monitor photoreceptor OS response evoked by a rectangular-shaped visible light flash. Stimulus-evoked photoreceptor OS length change and transverse distortion were quantitatively calculated.
High spatiotemporal resolution NIR imaging revealed rapid rod OS length change correlated with visible light stimulation. The magnitude and direction of the rod OS changes varied within the area covered by the rectangle-shaped stimulus pattern. In the center of the stimulus pattern, transient rod OS shrinkage was observed; while in the periphery of the stimulus pattern, transient rod tip shift towards the stimulus center was recorded.
Our experimental result and theoretical analysis indicate that the TRP might reflect unbalanced rod OS disc-shape change due to localized pigment bleaching and phototransduction. Further investigation is required to understand biochemical mechanism of the observed rod OS kinetics. Better study of the TRP may provide a noninvasive biomarker to enable early detection of age-related macular degeneration (AMD) and other diseases that are known to produce retinal photoreceptor dysfunctions.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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