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Vivek Jay Srinivasan, Shau Poh Chong, Marcel Trerice Bernucci; Spectroscopic imaging of the outer retina with visible light OCT. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5444.
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© ARVO (1962-2015); The Authors (2016-present)
The absorption of visible photons by photo pigment in the retina is the beginning of photo transduction that underlies visual perception, and numerous chromophores in the retina or its blood supply absorb visible light. Yet, Optical Coherence Tomography currently uses near-infrared (NIR) light. While near-infrared light can delineate layers in the retina based on NIR light scattering, visible light offers new diagnostic avenues. Here we hypothesize that spectroscopic visible light OCT can assess chromophores in the outer retina of the human eye.
A high-speed, fiber-based visible light spectral / Fourier domain OCT system was constructed for in vivo imaging of the human retina. For the data shown here, a sensitivity of 94 dB with an incident power of 100 microwatts and an axial scan rate of 10,000 axial scans per second was used, but 3D imaging speeds of up to 70,000 axial scans per second were also achieved. A maximal axial resolution of <2 microns (using the whole spectral bandwidth) and axial imaging range of ~1.6 mm were achieved in the retina.
Spectroscopic imaging of the human retina is shown in the Figure. Images with ~4 micron resolution were generated by dividing the visible light spectrum into non-overlapping sub-bands centered at 560 nm and 620 nm, and are shown in true color. Axial signal profiles in each sub-band were normalized to the Inner Limiting Membrane (ILM) reflection. The inner retinal layers as well as the 6 major bands of the outer retina are clearly resolved. In general, signal from the inner retina is higher at shorter wavelengths, while signal from the more distal outer retinal layers is higher at longer wavelengths.
Visible light OCT affords the unique opportunity to interrogate the outer retina with high resolution spectroscopically. Axial signal profiles are consistent with the chromophore distribution and optical properties of the retina.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Split-spectrum analysis of OCT retinal morphology. (A) Axial signal profiles in each sub-band were normalized to the ILM reflection and averaged across a region of interest, before plotting on a logarithmic scale. (B) Axial signal profiles of the outer retina, plotted on a linear scale, show that distinctive outer retinal layers can be visualized.
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