Corneal hydration assessment indicator based on terahertz time domain spectroscopy

Abstract

Terahertz technology has shown broad prospects for measuring corneal water content, which is an important parameter of ocular health. Based on terahertz time-domain spectroscopy, a new indicator named characteristic ratio (CR) of the sum of low (0.2-0.7 THz) and high (0.7-1.0 THz) frequency spectral intensities, for characterizing corneal hydration is introduced in this work. CR is calculated from the real-time reflection spectra after error elimination of ex vivo human corneal stroma samples which is collected during dehydration under natural conditions (temperature: 22.4 ± 0.3°C; humidity: 20.0 ± 3%). The corresponding relationships between CR and corneal water content are reported. Comparing the linear fitting results with the published similar study, the coefficients of variation of the fitting slope and intercept are 39.4% and 27.6% lower, respectively. This indicates that this approach has the potential to achieve corneal water content in-vivo detection in the future.

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

“…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).…”

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

“…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…”

“…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.…”

“…THz sensing corneal tissue is an expanding research topic that has been investigated by various research groups [1][2][3][4].…”

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

“…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.…”