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Shuliang Jiao, Tan Liu, Byron L Lam, Rong Wen; Imaging rhodopsin molecular contrast in vivo by optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5295. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To develop and validate a novel visible OCT technology for imaging the molecular contrast of rhodopsin in vivo. The ultimate goal of the study is to provide an imaging tool to assess the functions of rod photoreceptors.
Rhodopsin, the light-sensing molecule in the outer segments of rod photoreceptors, is responsible for converting light into neuronal signals in a process known as phototransduction. After absorbing a photon, rhodopsin undergoes conformational changes with a dramatic shift in its absorption spectrum: the maximum absorption peak shifts from 500 nm to 380 nm. This absorption change, known as rhodopsin photo-bleaching, provides a contrast to image rhodopsin. We report a novel 3-D retinal densitometry technique based on visible-light OCT for in vivo molecular imaging of rhodopsin. The system uses a light source centered at 532 nm closing to the peak absorption wavelength. With a bandwidth of 9.3 nm the system achieved a depth resolution of 13 micro-meters in air. The depth resolution allows the visualization and segmentation of the location where the absorption change occurs and provides an accurate assessment of rhodopsin content.
We have applied the technology to image Sprague Dawley rats. The technology has successfully revealed the depth-resolved rhodopsin distribution in the retina, and thus provides direct visualization of the photon propagation pathways. We have designed and successfully performed a pattern bleach experiment, the results of which is shown in the figure. The calculated image clearly showed the bleached strip of rhodopsin in both the projection image of the 3D OCT data an the depth resolved cross-sectional images. The results proved conclusively that our technology is able to image rhodopsin distribution in vivo.
Rhodopsin VIS-OCT can be used to quantitatively image rhodopsin distribution and thus assess the distribution of functional rod photoreceptors in the retina. Rhodopsin VIS-OCT can be adapted into a clinic tool for the diagnosis and severity assessment of a variety of retinal conditions.
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