Full-field spatially incoherent illumination interferometry: a spatial resolution almost insensitive to aberrations

Xiao, Peng; Fink, Mathias; Boccara, Albert Claude

doi:10.1364/ol.41.003920

Cited by 49 publications

(44 citation statements)

References 15 publications

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“…This allowed for efficient correction of ocular aberrations for retinal images acquired in vivo using post processing techniques [62]. Recently, an interesting effect could be observed when using full field OCT in combination with a spatially incoherent light source [63]. In such a system, aberrations will affect only the signal intensity and not the image sharpness.…”

Section: Computational Wavefront Correctionmentioning

confidence: 99%

Review of adaptive optics OCT (AO-OCT): principles and applications for retinal imaging [Invited]

Pircher

Zawadzki

2017

Biomed. Opt. Express

170

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Abstract:In vivo imaging of the human retina with a resolution that allows visualization of cellular structures has proven to be essential to broaden our knowledge about the physiology of this precious and very complex neural tissue that enables the first steps in vision. Many pathologic changes originate from functional and structural alterations on a cellular scale, long before any degradation in vision can be noted. Therefore, it is important to investigate these tissues with a sufficient level of detail in order to better understand associated disease development or the effects of therapeutic intervention. Optical retinal imaging modalities rely on the optical elements of the eye itself (mainly the cornea and lens) to produce retinal images and are therefore affected by the specific arrangement of these elements and possible imperfections in curvature. Thus, aberrations are introduced to the imaging light and image quality is degraded. To compensate for these aberrations, adaptive optics (AO), a technology initially developed in astronomy, has been utilized. However, the axial sectioning provided by retinal AO-based fundus cameras and scanning laser ophthalmoscope instruments is limited to tens of micrometers because of the rather small available numerical aperture of the eye. To overcome this limitation and thus achieve much higher axial sectioning in the order of 2-5µm, AO has been combined with optical coherence tomography (OCT) into AO-OCT. This enabled for the first time in vivo volumetric retinal imaging with high isotropic resolution. This article summarizes the technical aspects of AO-OCT and provides an overview on its various implementations and some of its clinical applications. In addition, latest developments in the field, such as computational AO-OCT and wavefront sensor less AO-OCT, are covered. 1178-1181 (1991). 2. M. Wojtkowski, B. Kaluzny, and R. J. Zawadzki, "New directions in ophthalmic optical coherence tomography," Optom. Vis. Sci. 89(5), 524-542 (2012). 3. T. E. de Carlo, A. Romano, N. K. Waheed, and J. S. Duker, "A review of optical coherence tomography angiography (OCTA)," Int J Retina Vitreous 1(5), 5 (2015). 4. W. Drexler and J. G. Fujimoto, "State-of-the-art retinal optical coherence tomography," Prog. Retin. Eye Res.27(1), 45-88 (2008). 5. G. Walsh, W. N. Charman, and H. C. Howland, "Objective technique for the determination of monochromatic aberrations of the human eye," J. Opt. Soc. Am. A 1(9), 987-992 (1984). 6. J. Liang and D. R. Williams, "Aberrations and retinal image quality of the normal human eye," J. Opt. Soc. Am.A 14(11), 2873-2883 (1997). Office, 2014). 27. J. Liang, B. Grimm, S. Goelz, and J. F. Bille, "Objective measurement of wave aberrations of the human eye with the use of a Hartmann-Shack wave-front sensor," J. Opt. Soc. Am. A 11(7), 1949-1957 (1994). 28. M. Laslandes, M. Salas, C. K. Hitzenberger, and M. Pircher, "Influence of wave-front sampling in adaptive optics retinal imaging," Biomed. Opt. Express 8(2), 1083-1100 (2017). 29. S. Tuohy and A. G. Podoleanu,...

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Section: Computational Wavefront Correctionmentioning

confidence: 99%

Review of adaptive optics OCT (AO-OCT): principles and applications for retinal imaging [Invited]

Pircher

Zawadzki

2017

Biomed. Opt. Express

170

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“…This resolution is not degraded by the speckle, because the incoherent light source is used. Additionally, resolution in FFOCT is not lowered by the geometrical aberrations 14 . FFOCT has been shown in a variety of applications, including imaging of biopsies of various tissues, studies in developmental biology, in vivo endoscopy, material characterization 13 , internal fingerprint imaging 15 , characterization of various ex vivo tissues from the anterior and posterior segments of animal eyes 16 and in vivo imaging of the anterior segment of a rat the in vivo human cornea 1 .…”

Section: Introductionmentioning

confidence: 99%

In vivo imaging through the entire thickness of human cornea by full-field optical coherence tomography

Mazlin

Xiao

Dalimier

et al. 2018

Ophthalmic Technologies XXVIII

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Despite obvious improvements in visualization of the in vivo cornea through the faster imaging speeds and higher axial resolutions, cellular imaging stays unresolvable task for OCT, as en face viewing with a high lateral resolution is required. The latter is possible with FFOCT, a method that relies on a camera, moderate numerical aperture (NA) objectives and an incoherent light source to provide en face images with a micrometer-level resolution. Recently, we for the first time demonstrated the ability of FFOCT to capture images from the in vivo human cornea 1 . In the current paper we present an extensive study of appearance of healthy in vivo human corneas under FFOCT examination. En face corneal images with a micrometer-level resolution were obtained from the three healthy subjects. For each subject it was possible to acquire images through the entire corneal depth and visualize the epithelium structures, Bowman's layer, sub-basal nerve plexus (SNP) fibers, anterior, middle and posterior stroma, endothelial cells with nuclei. Dimensions and densities of the structures visible with FFOCT, are in agreement with those seen by other cornea imaging methods. Cellular-level details in the images obtained together with the relatively large field-of-view (FOV) and contactless way of imaging make this device a promising candidate for becoming a new tool in ophthalmological diagnostics.

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“…This might be because we are not correcting the aberrations in the eye, which affects the signal level of FFOCT, as explained in Ref. [25]. Also, the smaller axial sectioning offered by FFOCT selects the signal from a thinner retinal layer, which would give a relatively lower signal level.…”

mentioning

confidence: 98%

“…With spatially incoherent illumination, cross talk is severely inhibited in FFOCT compared with wide-field OCTs that use spatially coherent illumination [24]. Moreover, the use of spatially incoherent illumination in FFOCT offers another advantage that we have demonstrated recently: the lateral resolution is independent of aberrations that only affect the FFOCT signal level [or signal-to-noise ratio (SNR)] [25], which is not the case for OCTs with spatially coherent illumination. In terms of human retinal imaging, the effects of chromatic aberration would also be limited, as FFOCT uses illumination with bandwidth of only tens of nanometers and has millimeter field of view.…”

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confidence: 99%

In vivo high-resolution human retinal imaging with wavefront-correctionless full-field OCT

Xiao¹,

Mazlin²,

Grieve³

et al. 2018

Optica

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As the lateral resolution of full-field optical coherence tomography (FFOCT) with spatially incoherent illumination has been shown to be insensitive to aberrations, we demonstrate high-resolution en face FFOCT retinal imaging without wavefront correction in the human eye in vivo for the first time, to our knowledge. A combination of FFOCT with spectraldomain OCT (SDOCT) is applied for real-time matching of the optical path lengths (OPLs) of FFOCT. Through the realtime cross-sectional SDOCT images, the OPL of the FFOCT reference arm is matched with different retinal layers in the FFOCT sample arm. Thus, diffraction-limited FFOCT images of multiple retinal layers are acquired at both the near periphery and the fovea. The en face FFOCT retinal images reveal information about various structures, such as the nerve fiber orientation, the blood vessel distribution, and the photoreceptor mosaic. During its 25 years of development, optical coherence tomography (OCT) has become a powerful imaging modality in biomedical and clinical studies [1,2]. It has achieved great success in ophthalmology [3], especially in retinal imaging for which it has been entitled the "virtual biopsy" for human retina [4]. Compared with typical retinal imaging modalities like fundus cameras [5] or scanning laser ophthalmoscopy (SLO) [6], in which axial resolution is limited by the finite size of the eye's pupil, OCT offers much higher axial sectioning, as the lateral and axial resolutions are decoupled. The high-resolution cross-sectional depth exploration of the retinal layers offers important information about pathologies for early diagnosis of disease and for tracing disease evolution [7][8][9]. While doctors are capable of interpreting crosssectional OCT slices, there is nevertheless a need for en face views, as shown by the continued use of en face techniques such as fundus cameras or SLO. Thanks to the speed improvement, OCT systems can provide en face retinal images by doing real-time 3Dimaging [10][11][12]. Nevertheless, due to the requirement of large depth of focus, low NA is typically used in traditional OCT, resulting in relatively low spatial resolution compared with high-NA systems. To ensure high transverse resolution, en face flying spot OCT has been applied for human retinal imaging, which achieves retinal en face images with transverse scanning [13,14]. To be able to realize close to diffraction-limited lateral resolution in OCT retinal imaging, complex hardware adaptive optics (AO) [15][16][17][18][19] or computational AO [20][21][22] would also be needed to correct the aberrations induced by the imperfections of the cornea and lens in the anterior chamber.Full-field OCT (FFOCT) is a kind of time-domain en face parallel OCT that takes images perpendicular to the optical axis without scanning. By using high-NA microscope objectives in a Linnik interferometer, FFOCT is able to achieve standard microscope spatial resolution [23]. With spatially incoherent illumination, cross talk is severely inhibited in FFOCT compared with wide-...

show abstract

Full-field spatially incoherent illumination interferometry: a spatial resolution almost insensitive to aberrations

Cited by 49 publications

References 15 publications

Review of adaptive optics OCT (AO-OCT): principles and applications for retinal imaging [Invited]

Review of adaptive optics OCT (AO-OCT): principles and applications for retinal imaging [Invited]

In vivo imaging through the entire thickness of human cornea by full-field optical coherence tomography

In vivo high-resolution human retinal imaging with wavefront-correctionless full-field OCT

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