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VIMAL PRABHU PANDIYAN, Aiden Maloney Bertelli, Ramkumar Sabesan; High speed, spectral domain, line field OCT. Invest. Ophthalmol. Vis. Sci. 2018;59(9):663.
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© ARVO (1962-2015); The Authors (2016-present)
Measuring depth-resolved optical path length changes in response to light stimuli necessitates high-speed and phase-stable OCT image acquisition to overcome eye motion in the human retina. Here we characterize the limits of phase sensitivity obtainable in a high-speed line-field OCT and explore whether such an imaging configuration is suitable for assessing retinal function in response to photostimulation.
A free space, line field spectral domain OCT was designed and constructed. A superluminescent diode centered at 840 nm with a 30 nm FWHM was used. A cylindrical lens was used to generate a 2.3 deg. line illumination on the retina. The sample arm consisted of a 1D galvo to enable the recording of volumes by scanning the line field on the retina and a badal system for adjusting focus. The spectrometer consisted of a 1200 lp/mm grating and a high-speed 2D camera. 2D tomograms consisting of spatial (200 - 300 pixels) and spectral (768 pixels) were recorded with maximum speeds up to 16.2 kHz. Phase sensitivity (standard deviation of phase vs. time) was assessed from the front and back surface of a coverslip. MB-scan mode images and complete volumes were obtained at 5 deg. temporal eccentricity in human retina and assessed for phase sensitivity at the nerve fiber layer and IS/OS junction.
The measured axial resolution was 10.8 μm. The sensitivity of the system was 78.2 dB at the lowest exposure time of 62 μs. The phase sensitivity was 4.4 mrad (optical path length in air = 0.32nm) at 50 dB SNR. A ±3 nm axial amplitude was measured from a piezo transducer held under a small sinusoidal voltage vs. time. In the human retina, scanning the line-field at 200 points allowed maximum volume rates of 80 volumes/s. In an MB-scan at 16kHz B-scan rate, the phase noise floor per pixel was shot-noise limited without spatial or temporal averaging. Along the line field, the sensitivity at the nerve fiber layer and IS/OS were 66 mrad and 160 mrad at 22.78 dB and 18 dB signal-to-noise ratio, respectively.
Fast volume acquisition and high phase stability demonstrate the potential of high-speed, line field, spectral domain OCT for detecting stimulus induced functional changes in the retina.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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