Corneal hydration assessment indicator based on terahertz time domain spectroscopy

Yao, Jiali; Ma, Jianjun; Zhao, Jiehui; Qi, Pengfei; Li, Mengdi; Lin, Li; Sun, Lu; Wang, Xiaolei; Liu, Weiwei; Wang, Yan

doi:10.1364/boe.387826

Cited by 13 publications

(6 citation statements)

References 30 publications

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“…Then the experiment group was scanned to induce collagen CXL effects by a femtosecond laser writing system (Figure 2D, see Methods for more details) with a focal volume of ~49 μm in the axial direction and ~5 μm in the lateral direction. During scanning procedure, the corneal stroma was moistened by dripping previously prepared 0.1% RF solution to prevent drying every 2 ~ 3 min [53, 54]. In the focusing region, the excited photosensitizer RF generated oxygen free radicals, resulting in CXL within or between collagen fibers (Figure 2E).…”

Section: Resultsmentioning

confidence: 99%

Two‐photon collagen crosslinking in ex vivo human corneal lenticules induced by near‐infrared femtosecond laser

Cheng

Zhang

Chang

et al. 2022

Journal of Biophotonics

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Myopia and keratoconus have become common corneal diseases that threaten the quality of human vision, and keratoconus is one of the most common indications for corneal transplantation worldwide. Collagen crosslinking (CXL) using riboflavin and ultraviolet A (UVA) light is an effective approach for treating ophthalmic disorders and has been shown clinically not only to arrest further progression of keratoconus but also to improve refractive power for cornea. However, CXL surgery irradiated by UVA has various potential risks such as surface damage and endothelial cell damage. Here, near‐infrared femtosecond laser‐based two‐photon CXL was first applied to ex vivo human corneal stroma, operating at low photon energy with high precision and stability. After two‐photon CXL, the corneal stiffness can be enhanced by 300% without significantly reducing corneal transparency. These findings illustrate the optimized direction that depositing high pulses energy in corneal focal volume (not exceeding damage threshold), and pave the way to 3D CXL of in vivo human cornea with higher safety, precision, and efficacy.

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Section: Resultsmentioning

confidence: 99%

Two‐photon collagen crosslinking in ex vivo human corneal lenticules induced by near‐infrared femtosecond laser

Cheng

Zhang

Chang

et al. 2022

Journal of Biophotonics

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“…The AGBB axial extent is ~ 58 mm and denoted by zmax in Fig. 1(a) and equation (1) where ω(f) is the frequency dependent beam radius at the axicon surface, β 0 is the inclination angle of the rays defined by the external cone angle α and lens material permittivity εr as in equations ( 2) [20]. Equation (3) shows that the axially directed k-vector, k z , is less than the free space k and thus the phase velocity is superluminal [21]; υ p ~ 1.04c 0 for α = 25 o…”

Section: A Backgroundmentioning

confidence: 99%

“…The RoC was varied from 7 mm to 11 mm in steps of 0.5 mm for a total of 9 target spheres. The axial position ranged from 5 to 51 mm referenced to the lens conical tip and corresponding to the approximate Bessel beam regime predicted by equation (1). The simulation distributed 10,000 randomly generated skew rays, subject to a Gaussian pdf, with the source plane located at hyperbolic surface focal point.…”

Section: B Ray Tracing Simulation Of Hyperbolic Axicon Lensmentioning

confidence: 99%

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Submillimeter-Wave Cornea Phantom Sensing Over an Extended Depth of Field With an Axicon-Generated Bessel Beam

Baggio

Tamminen

Lamberg

et al. 2023

IEEE Trans. THz Sci. Technol.

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The feasibility of a 220 -330 GHz zero order axicon generated Bessel beam for corneal water content was explored. Simulation and experimental data from the 25-degree cone angle hyperbolic-axicon lens illuminating metallic spherical targets demonstrate a monotonically decreasing, band integrated, backscatter intensity for increasing radius of curvature from 7 -11 mm, when lens reflector and optical axis are aligned. Further, for radii >= 9.5 mm, maximum signal was obtained with a 1 mm transverse displacement between lens and reflector optical axes arising from spatial correlation between main lobe and out of phase side lobes. Thickness and permittivity parameter estimation experiments were performed on an 8 mm radius of curvature, 1 mm thick fused quartz dome over a 10 mm axial span. Extracted thickness and permittivity varied by less than ~ 25 μm and 0.2 respectively after correction for superluminal velocity. Estimated water permittivity and thickness of water backed gelatin phantoms showed significantly more variation due to a time varying radius of curvature. To the best of our knowledge, this is the first work that describes axicon generated Bessel beam measurements of layered spheres with varying radii of curvature, in the submillimeter range.

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“…For THz applications, THz systems commonly require various passive THz devices [17][18][19], including THz reflector, THz polarizer, THz lens, THz beam splitter, etc. Among these devices, THz beam splitter plays a key role in THz systems, such as THz spectroscopy and THz communication [20,21]. In particular, in a hybrid integrated communication system composed of optical fiber communication and THz communication [22][23][24], a special multispectral beam splitter is of great use for optimizing light transmission paths and improving system performances.…”

Section: Introductionmentioning

confidence: 99%

Broadband, optically transparent and highly flexible multispectral beam splitter based on Ag nanowires/graphene composite film for hybrid optical systems

Lai

Fang

Liu

et al. 2021

J. Phys. D: Appl. Phys.

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The research on novel terahertz (THz) devices with high performance is in rapid ascent in order to promote applications of THz technology. In this paper, we propose a broadband, optically transparent and highly flexible multispectral beam splitter based on Ag nanowires/graphene (ANWG) composite film on polyethylene terephthalate film substrates. The properties of the ANWG-based beam splitters are investigated, which exhibit a broadband THz reflectance of about 90%, a high optical transmittance of over 86% in the visible range, and excellent mechanical flexibility. The THz experimental result of the ANWG-based beam splitter is close to those of numerical simulations using a theoretical model. In comparison with conventional THz beam splitters, the ANWG-based beam splitter possesses excellent light-splitting performances for both transmitting visible light and reflecting THz radiation, and the device can significantly improve the overall performance of THz optical systems. Moreover, the device can be effectively applied in the visible/infrared imaging systems to implement multispectral imaging. Our concept provides a promising route for realizing compact hybrid optical systems, and it has great potential for commercial applications.

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Corneal hydration assessment indicator based on terahertz time domain spectroscopy

Cited by 13 publications

References 30 publications

Two‐photon collagen crosslinking in ex vivo human corneal lenticules induced by near‐infrared femtosecond laser

Two‐photon collagen crosslinking in ex vivo human corneal lenticules induced by near‐infrared femtosecond laser

Submillimeter-Wave Cornea Phantom Sensing Over an Extended Depth of Field With an Axicon-Generated Bessel Beam

Broadband, optically transparent and highly flexible multispectral beam splitter based on Ag nanowires/graphene composite film for hybrid optical systems

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