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Haroun Al-Mohamedi, Andreas Prinz, Theo Oltrup, Martin Leitritz, Thomas Bende; In vivo full range dual-wavelength Fourier domain optical coherence tomography. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1897.
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To increase the measurement accuracy of the biometric data detection, and improving the quality of the real-time imaging of the whole eye.
A dual-wavelength Fourier domain optical coherence tomography was built. It uses a Michelson interferometer with two wide-spectrum Superluminescent Diodes(SLD). The first source emits light with a central wavelength of 840 nm and a bandwidth of 50 nm (SLD-371-HP, Superlum, Ireland). The second has a central wavelength of 954 nm and a bandwidth of 34 nm (SLD-481-MP1, Superlum, Ireland).The light coming from the SLDs is divided by a 50:50 beam splitter into the measurement path and the reference path. The emissions of the SLDs are filtered by a long-pass filter (900 nm) in front of the reference mirror.The reflected or scattered fraction of the light from the measurement path interferes with the reflected portion from the reference path. The light is spectrally decomposed using a reflective diffraction grating (1800 lines/mm), the whole spectrum captured with two CCD line sensors with 4096 pixel.The capabilities of the system were tested by measurements of a self-made human model eye with interfaces comparable to those of a biological eye, which was mounted into the measuring path.
The imaging depth of the system was 40 mm; 20 mm for the anterior chamber using the wavelength of 954 nm, and 20 mm for the posterior chamber using the wavelength of 840nm.The SNR was 88dB for the anterior part, and 98dB for the posterior part. The axial imaging resolution in the anterior part was <= 6μm and 11μm for the posterior part. The measurements show clearly the interfaces of the optical components and their contours. The measurement of the whole eye takes place in two combined segments with acquisition rate up to 50,000 A-scans per second.The interfaces of the front and back surface of the cornea, the front and back surfaces of the lens and the retina can be seen clearly. The measurements were carried out with a total light power of 700μW.
This system realizes a real time imaging of the whole eye with a quasi constant SNR over the entire measuring path. The biometric data detection and the imaging of the eye were carried out according to the safety standards. The measured radiuses and distances are comparable to the given and measured by IOL Master 700. Improving the signal processing to maximize SNR will better enable the providing of very high quality images.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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