Fast Fourier Transform–Based Analysis of Second-Harmonic Generation Image in Keratoconic Cornea

Lo, Wen; Chen, Wei‐Liang; Hsueh, Chiu Mei; Ghazaryan, Ara; Chen, Shean-Jen; Hui‐Kang, David; Chen, Dong; Tan, Hsin Yuan

doi:10.1167/iovs.10-6697

Cited by 44 publications

(54 citation statements)

References 30 publications

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“…As indicator of the number of fibers that deviate from the preferred orientation they used the standard fitting error. A FT analysis was also recently made to compare structural alteration between normal and keratoconic corneas imaged with SHG microscopy [15]. The AR served as a quantitative measure of fiber direction determination.…”

Section: Introductionmentioning

confidence: 99%

Analysis of spatial lamellar distribution from adaptive-optics second harmonic generation corneal images

Bueno

Palacios

Chessey

et al. 2013

Biomed. Opt. Express

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The spatial organization of stromal collagen of ex-vivo corneas has been quantified in adaptive-optics second harmonic generation (SHG) images by means of an optimized Fourier transform (FT) based analysis. At a particular depth location, adjacent lamellae often present similar orientations and run parallel to the corneal surface. However this pattern might be combined with interweaved collagen bundles leading to crosshatched structures with different orientations. The procedure here reported provides us with both principal and crosshatched angles. This is also able to automatically distinguish a random distribution from a cross-shaped one, since it uses the ratio of the axes lengths of the best-fitted ellipse of the FT data as an auxiliary parameter. The technique has successfully been applied to SHG images of healthy corneas (both stroma and Bowman’s layer) of different species and to corneas undergoing cross-linking treatment.

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Section: Introductionmentioning

confidence: 99%

Analysis of spatial lamellar distribution from adaptive-optics second harmonic generation corneal images

Bueno

Palacios

Chessey

et al. 2013

Biomed. Opt. Express

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“…SHG techniques have also been used to analyze pathological corneas suffering from keratoconus [17,18], edema [19] or bullous keratopathy [20] among others. The spatial changes in the distribution of collagen fibers in control and diseased corneas has been also reported [21][22][23].…”

Section: Introductionmentioning

confidence: 86%

“…Consequently, the deeper the location within the sample to be imaged, the lower the quality of the acquired image. This is a limitation in SHG imaging of ocular tissues, where some pathologies or non-controlled structural changes might be placed at deeper locations [17][18][19][20][21]. Adaptive optics has been used to improve SHG imaging of corneal tissues at the posterior stroma [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Comparison of second harmonic microscopy images of collagen-based ocular tissues with 800 and 1045 nm

Bueno

Ávila

Artal

2017

Biomed. Opt. Express

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Second harmonic generation (SHG) imaging is a well-suited multiphoton technique allowing visualization of biological tissues mainly composed of collagen with submicron resolution. Despite its inherent confocal properties, imaging of deeper layers within thick samples has still some limitations. Although the use of longer wavelengths might help to overcome this, the dependence between SHG signals and wavelength is still under discussion. We report here on the dependence with wavelength of SHG signals from collagen-based ocular tissues. The quality of SHG images for two commonly used excitation wavelengths (800 and 1045 nm) is studied. The analysis of the collagen structural information reveals that the information provided by both wavelengths is similar. It was also found that, independently of the depth location, 1045-nm SHG images presented always lower signal levels than those acquired with 800 nm. However, the contrast of the former images was higher, what may improve the visualization of certain features of interest. "Abnormalities of stromal structure in the bullous keratopathy cornea identified by second harmonic generation imaging microscopy," Invest.

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“…Over the past decade, NLO SHG imaging has been used to evaluate corneal collagen in normal corneas from human (Aptel et al, 2010; Han et al, 2005; Morishige et al, 2006), mouse (Lo et al, 2006), pig (Jay et al, 2008; Teng et al, 2006; Wang et al, 2008), and rabbit (Morishige et al, 2006), as well as used to study pathologic conditions, such as keratoconus (Morishige et al, 2007; Tan et al, 2006), intrastromal laser ablation (Han et al, 2004; Wang and Halbhuber, 2006), thermal injury (Lo et al, 2009; Tan et al, 2005), transgenic mouse models (Lyubovitsky et al, 2006), infectious keratitis (Tan et al, 2007), wound healing (Farid et al, 2008; Nien et al, 2011; Teng et al, 2007), corneal edema (Hsueh et al, 2009; Wu and Yeh, 2008), collagen crosslinking (Bueno et al, 2011), and diabetes (Latour et al, 2012b). More recently, objective measures have been developed to characterize collagen orientation by using fast Fourier transformation (Ghazaryan et al, 2013; Lau et al, 2012; Lo et al, 2012; Mega et al, 2012; Rao et al, 2009; Tan et al, 2013) and by taking advantage of the unique polarization dependent properties of SHG signals (Latour et al, 2012a; Stoller et al, 2002; Tuer et al, 2012). …”

Section: Non-linear Optical (Nlo) Imaging Of Second Harmonic Genermentioning

confidence: 99%

From nano to macro: Studying the hierarchical structure of the corneal extracellular matrix

Quantock

Winkler

Parfitt

et al. 2015

Experimental Eye Research

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In this review, we discuss current methods for studying ocular extracellular matrix (ECM) assembly from the ‘nano’ to the ‘macro’ levels of hierarchical organization. Since collagen is the major structural protein in the eye, providing mechanical strength and controlling ocular shape, the methods presented focus on understanding the molecular assembly of collagen at the nanometer level using x-ray scattering through to the millimeter to centimeter level using nonlinear optical (NLO) imaging of second harmonic generated (SHG) signals. Three-dimensional analysis of ECM structure is also discussed, including electron tomography, serial block face scanning electron microscopy (SBF-SEM) and digital image reconstruction. Techniques to detect non-collagenous structural components of the ECM are also presented, and these include immunoelectron microscopy and staining with cationic dyes. Together, these various approaches are providing new insights into the structural blueprint of the ocular ECM, and in particular that of the cornea, which impacts upon our current understanding of the control of corneal shape, pathogenic mechanisms underlying ectatic disorders of the cornea and the potential for corneal tissue engineering.

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Fast Fourier Transform–Based Analysis of Second-Harmonic Generation Image in Keratoconic Cornea

Cited by 44 publications

References 30 publications

Analysis of spatial lamellar distribution from adaptive-optics second harmonic generation corneal images

Analysis of spatial lamellar distribution from adaptive-optics second harmonic generation corneal images

Comparison of second harmonic microscopy images of collagen-based ocular tissues with 800 and 1045 nm

From nano to macro: Studying the hierarchical structure of the corneal extracellular matrix

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