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Pengfei Zhang, Mayank Goswami, SUMAN MANNA, Ratheesh Meleppata, Robert J Zawadzki, Edward N. Pugh; Novel features of optophysiological signals from mouse rod outer segment tips observed by optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5825. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To develop more detailed model of the visible light-induced retina changes in rod outer segment (ROS) length and tip position, and in light scattering, measured by Optical Coherence Tomography (OCT).
The dark-adapted retinas of albino (Balb/c) mice were imaged in vivo with a custom SLO/OCT system during and after controlled light stimulation. SLO (488 nm) was used to bleach controlled fractions of rhodopsin. NIR broadband OCT (132 nm bandwidth centered at 860 nm) was used to extract optophysio-logical responses to light stimulus. Time dependent changes in position and intensity of different photoreceptor bands as measured by OCT were recorded and analyzed.
The lack of melanin in albino mice allowed clear visualization of backscatter from rod outer segment tips (ROST) and from Bruch’s membrane (BrM). The axial PSF was estimated (Fig. 1 (a)), and used to deconvolve OCT axial profiles after 10% rhodopsin bleach (Fig. 1 (b)). The deconvolved profiles (Fig. 1 (c)) reveal a distinct source of light scattering located in the distal portion of ROS, near the ROST. This signal can be well described as a sum of Gaussian functions (Fig. 1 (d)). Based on these results, each scattering locus is characterized by three parameters: position related to BrM, backscatter maximum and its FWHM (full width at half maximum) signal. All these were measured and will be used to assist in future modeling.
Light-stimulated optophysiological changes of the retina in response to a controlled bleaching exposure as measured by OCT has been studied extensively, with focus on signal intensity and signal positions. These results confirm previous ones measuring ROS layer thickness changes after such exposures, and reveal a novel source of bleaching-induced scattering near the ROST that may reflect changes in ROS structure accompanying swelling. A model of the distal ROS and ROST that includes local variation in osmotic swelling and refractive index changes will be formulated to further understand these optophysiological signals.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Fig.1 Results: (a) estimate the system PSF, (b) original time dependent OCT signal from outer retina, (c) result of deconvolution of signal in (b) with PSF, (d), two Gaussian fit of the signals from middle of OS and ROST.
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