Ultrahigh-Speed Optical Coherence Tomography for Three-Dimensional and En Face Imaging of the Retina and Optic Nerve Head

Abstract

Purpose To demonstrate ultrahigh-speed optical coherence tomography (OCT) imaging of the retina and optic nerve head at 249,000 axial scans per second and a wavelength of 1060 nm. To investigate methods for visualization of the retina, choroid, and optic nerve using high-density sampling enabled by improved imaging speed. Methods A swept-source OCT retinal imaging system operating at a speed of 249,000 axial scans per second was developed. Imaging of the retina, choroid, and optic nerve were performed. Display methods such as speckle reduction, slicing along arbitrary planes, en face visualization of reflectance from specific retinal layers, and image compounding were investigated. Results High-definition and three-dimensional (3D) imaging of the normal retina and optic nerve head were performed. Increased light penetration at 1060 nm enabled improved visualization of the choroid, lamina cribrosa, and sclera. OCT fundus images and 3D visualizations were generated with higher pixel density and less motion artifacts than standard spectral/Fourier domain OCT. En face images enabled visualization of the porous structure of the lamina cribrosa, nerve fiber layer, choroid, photoreceptors, RPE, and capillaries of the inner retina. Conclusions Ultrahigh-speed OCT imaging of the retina and optic nerve head at 249,000 axial scans per second is possible. The improvement of ∼5 to 10× in imaging speed over commercial spectral/Fourier domain OCT technology enables higher density raster scan protocols and improved performance of en face visualization methods. The combination of the longer wavelength and ultrahigh imaging speed enables excellent visualization of the choroid, sclera, and lamina cribrosa.

Imaging chorioretinal vascular disease

“…Prototype Doppler OCT systems allow measurement of retinal blood flow by the assessment of light reflectivity changes in retinal blood vessels over short time periods. 37 'Swept-source' OCT systems allow significant increases in imaging sensitivity and speed (eg 4300 000 A-scans per second), through the use of a tunable laser, 38 whereas polarization-sensitive OCT may prove to encode much of the information provided by FAF. 39 Finally, the use of adaptive optics in OCT devices may increase the transverse resolution of OCT systems and provide cellular level detail.…”

Optical coherence tomography angiography in glaucoma diagnosis

“…Он рас-считывается как усредненное значение декорреля-ции в исследуемой зоне сетчатки, т.е. он зависит в том числе от средней величины микроциркуляции крови в капиллярах в этой зоне [24][25][26][27]. Важно под-черкнуть, что Flow Index содержит информацию не только о плотности сосудов, но и о скорости крово-тока в капиллярах.…”

Fourier Domain Optical Coherence Tomography for Retinal Imaging with 800-nm Swept Source: Real-time Resampling in k-domain

“…Recently, a swept source in the 1.0 μm region has been actively used for retina imaging because water absorption has a local minimum and the dispersion in water is near zero in the 1.0 μm region [16,17]. However, a broadband source centered in the 800 nm region rather than in the 1.0 μm region is favorable for obtaining high resolution [18].…”

“…Chinn et al [19] have developed an 840-nm swept source with a full-width at half-maximum (FWHM) of 20 nm, which utilizes a superluminescent light-emitting diode and a Littrow configuration with a grating and a resonant galvanometer scanner. Lim et al [20,21], Lee et al [22], and Srinivasan et al [17] introduced an 850-nm swept source with an FWHM over 35 nm employing semiconductor optical amplifiers (SOAs). Lim et al developed a swept source at 850 nm based on a ring cavity including a free-space isolator [20] or a linear cavity with only an optical fiber coupler (fiber loop mirror) [21].…”

“…They used the spectral filter comprised of a diffractive grating, achromatic lenses, and a polygon mirror. Lee et al and Srinivasan et al also constructed spectral filters on the basis of Littman and Littrow configurations, respectively [17,22]. These configurations included a diffractive grating and galvanometer scanner.…”