Volumetric retinal imaging with ultrahigh-resolution spectral-domain optical coherence tomography and adaptive optics using two broadband light sources

Abstract

Ultrabroadband sources, such as multiplexed superluminescent diodes (SLDs) and femtosecond lasers, have been successfully employed in adaptive optics optical coherence tomography (AO-OCT) systems for ultrahigh resolution retinal imaging. The large cost differential of these sources, however, motivates the need for a performance comparison. Here, we compare the performance of a Femtolasers Integral Ti:Sapphire laser and a Superlum BroadLighter T840, using the same AO-OCT system and the same subject. In addition, we investigate the capability of our instrument equipped with the Integral to capture volume images of the fovea and adjacent regions on a second subject using the AO to control focus in the retina and custom and freeware image registration software to reduce eye motion artifacts. Monochromatic ocular aberrations were corrected with a woofer-tweeter AO system. Coherence lengths of the Integral and BroadLighter were measured in vivo at 3.2 μm and 3.3 μm, respectively. The difference in dynamic range was 5 dB, close to the expected variability of the experiment. Individual cone photoreceptors, retinal capillaries and nerve fiber bundles were distinguished in all three dimensions with both sources. The acquired retinal volumes are provided for viewing in OSA ISP, allowing the reader to data mine at the microscope level.

Ultra-high resolution Fourier domain optical coherence tomography for old master paintings

“…Until recently, FDOCT using ultra-broad band sources only managed to achieve axial resolutions of a few microns in biological tissues [20][21][22][23][24][25][26][27][28][29]. Recent availability of commercial turn-key ultra-broad band supercontinuum sources has enabled < 2 µm axial resolution (in air) for Fourier domain OCTs [30,31].…”

Cellular Level Imaging of the Retina Using Optical Coherence Tomography

“…Though this resolution is sufficient to image retinal layers, identification of individual cells or sub-cellular structures is not possible. Pushing towards cellular imaging, advanced SLDs have been developed with wide spectral bandwidths ≥ 80 nm by multiplexing 2 or more SLDs, providing OCT axial resolutions of < 10 m Cense et al, 2009a;Hong et al, 2007;Ko et al, 2004;Potsaid et al, 2008;Zawadzki et al, 2005). A prototype of this ultrawideband SLD for OCT imaging was first demonstrated by Ko et al in 2004.…”

“…They used a Femtolasers Integral Ti:Sapph laser with a spectral bandwidth, center wavelength and power of 135 nm, 800 nm, and 60 mW, respectively (Cense et al, 2009a). In comparison, the BroadLighter, a multiplexed SLD, has 110 nm spectral bandwidth, 840 nm center wavelength and 12 mW of input power (Cense et al, 2009a).…”

Cellular imaging of the living human retina

“…With these UHR-AO-OCT systems, we have successfully created 3D retinal images of structures previously only visible with histology or invasive imaging, including the foveal microvasculature, bundles within the retinal nerve fiber layer, the fibers of Henle, the 3D photoreceptor mosaic, tiny drusen in age-related macular degeneration, and the tiny pores of the lamina cribosa of the optic nerve in normal and glaucoma patients 12,14 . Figure 3 shows a representative UHR-AO-OCT volume acquired in one subject.…”

“…Using this strategy, ultrahigh resolution (UHR) AO-OCT instruments have recently achieved an isotropic 3D resolution approaching 3 × 3 × 3µm 3 in retinal tissue (see Figure 1). [12][13][14] In addition to the roughly 3× improvement in lateral resolution, AO increases the instrument sensitivity (∼7dB) and reduces the lateral size of speckle noise (3×), an unwanted byproduct of the interferometric nature of OCT. Figure 2. The Indiana ultra-high-resolution adaptive-optic OCT retinal camera designed around a fiber-based Michelson interferometer composed of four channels: the source, reference, sample, and detector.…”