Purchase this article with an account.
Daniel Fechtig, Tilman Schmoll, Cedric Blatter, Rainer A Leitgeb; Structural and functional retinal imaging with MHz Line-field parallel swept source imaging (LPSI). Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4092.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
MHz OCT allows mitigating undesired influence of motion artifacts during retinal assessment, but comes in state-of-the-art point scanning OCT at the price of increased system complexity. By changing the paradigm from scanning to parallel OCT for in vivo retinal imaging the three-dimensional (3D) acquisition time is reduced without a trade-off between speed, sensitivity and technological requirements.
Line field parallel interferometric imaging (LPSI) is utilizing a commercially available swept source, a single-axis galvo-scanner and a line scan camera for recording 3D data with up to 1MHz A-scan rate. Besides line-focus illumination and parallel detection, we mitigate the necessity for high-speed sensor and laser technology by holographic full-range imaging, which allows for increasing the imaging speed by low sampling of the optical spectrum. High B-scan rates up to 1kHz further allow for implementation of lable-free optical angiography in 3D by calculating the inter B-scan speckle variance.
We achieve a detection sensitivity of 93.5 (96.5) dB at an equivalent A-scan rate of 1 (0.6) MHz. Fig. 1(a) was obtained by stitching 7 slightly overlapping non-averaged tomograms. The sensitivity and resolution are high enough to visualize the external limiting membrane (ELM), and to contrast the various layers of the inner retina. Despite the loss of confocality in one lateral dimension and the shorter center wavelength of 840nm, the signal intensity from the choroid is remarkably strong maintaining structural details. In Fig. 1(b) we feature a enface projection of micro-angiographic information. One single 3D stack corresponds to a lateral FOV of approx. 5-6° and is acquired in just 2.5 s.
Our results demonstrate for the first time competitive imaging sensitivity, resolution and speed with a parallel OCT modality. LPSI is in fact currently the fastest OCT device applied to retinal imaging and operating at a central wavelength window around 800 nm with a detection sensitivity of higher than 93.5 dB.
This PDF is available to Subscribers Only