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Michael Atlan, Serge Meimon, Leo Puyo, mathias fink, Jose Alain Sahel, Michel Paques; High-speed holographic imaging of the retina. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3126.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal blood flow plays a central role in the pathophysiology of many eye diseases, either through capillary occlusion, hypoperfusion or altered flow distribution. Quantitative monitoring of hemodynamic signals down to capillaries without contrast agent remains a challenging task. Here we present a promising technique for the analysis of human retinal blood flow, based on holographic interferometry on a high throughput camera.
We have developed off-axis holographic interferometry instruments for retinal imaging with near-infrared laser light, which enable coherent wide-field optical detection at extremely low irradiance levels, and permit recordings of light from the retina with high-speed cameras. Detection of blood flow contrasts in superficial retinal vessels was performed with a single-mode laser, and en-face depth-sectioning was investigated by time-domain and swept-source tomography, with a femtosecond laser and a tunable laser, respectively.
Blood flow contrasts in the vascular tree surrounding the optic nerve head in the retina of a pigmented rat were measured by recording 768*768 pixels interferograms at a sampling rate of 39 kHz (23 Gigapixels/s); retinal tissue exposure over 3 mm x 3 mm was limited to 1.6 mW of continuous wave, near-infrared laser radiation. The three first moments of the envelope of the short-time Fourier transform of the holograms enabled robust, high spatial and temporal resolution detection of Doppler contrasts. Color-coded dynamic bidimensional maps of pulsatile retinal blood flow contrasts signals over 400 x 400 pixels (~20° field) with a spatial resolution of ~8 microns and a temporal resolution of ~6.5 ms were obtained, and enabled to distinguish arteries from veins. The peak flow in veins occurred on average (±SD) 20 ms (±10) after the peak flow of arteries. In addition, proofs of concepts of time-domain and swept-source coherence tomography are also reported.
Holographic interferometry with laser light permits wide-field coherent imaging of the retina with high-speed cameras. Retinal blood flow contrasts were measured over a large field of view. Although the spatial resolution of the reported results cannot compare yet with state-of-the-art scanning optical coherence tomography methods, the reported imaging throughput of 23 Giga pixels per second paves the way towards the design of high-speed coherent imaging instruments for Doppler and tomographic imaging.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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