Abstract
The design of a multi-functional fiber-based Optical Coherence Tomography (OCT) system for human retinal imaging with < 2 micron axial resolution in tissue is described. A detailed noise characterization of two supercontinuum light sources with different pulse repetition rates is presented. The higher repetition rate and lower noise source is found to enable a sensitivity of 96 dB with 0.15 mW light power at the cornea and a 98 microsecond exposure time. Using a broadband (560 ± 50 nm), 90/10, fused single-mode fiber coupler designed for visible wavelengths, the sample arm is integrated into an ophthalmoscope platform, similar to current clinical OCT systems. To demonstrate the instrument's range of operation, in vivo structural retinal imaging is also shown at 0.15 mW exposure with 10,000 and 70,000 axial scans per second (the latter comparable to commercial OCT systems), and at 0.03 mW exposure and 10,000 axial scans per second (below maximum permissible continuous exposure levels). Lastly, in vivo spectroscopic imaging of anatomy, saturation, and hemoglobin content in the human retina is also demonstrated.
Highlights
Over the past decade, advances in high-speed, high-resolution Fourier domain Optical Coherence Tomography (FDOCT) for human retinal and optic nerve head imaging [1] have improved the diagnosis and monitoring of major eye diseases [2]
A variable neutral density filter (NDF) was used to adjust the reference power and a 20 mm water cell was placed in the beam path for dispersion balancing during retinal imaging
To compensate for differences between subject axial eye length and the 20 mm water cell (Fig. 1(A)), as well as fiber length mismatch between the arms, numerical dispersion compensation was applied to acquired images [29]
Summary
Advances in high-speed, high-resolution Fourier domain Optical Coherence Tomography (FDOCT) for human retinal and optic nerve head imaging [1] have improved the diagnosis and monitoring of major eye diseases [2]. For a given light exposure level and imaging speed, FDOCT methods, including spectral-domain (SD) OCT [1] and swept-source (SS) OCT [3], provide a > 20 dB increase in sensitivity compared to time-domain OCT [4,5,6], enabling faster imaging speed. The Fourier domain detection scheme provides access to both amplitude and phase of the complex OCT signal, facilitating Doppler [7], spectroscopic [8, 9], and angiographic imaging [10,11,12]. The narrow water absorption window around 1050 nm may limit the achievable axial resolution in the human eye
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