PURPOSE: The feasibility of Raman spectroscopy for the noninvasive assessment of axial corneal hydration was investigated. METHODS: A scanning confocal Raman spectroscopy system, with an axial resolution of 50 microns, was used to assess noninvasively the water (OH-bond) to protein (CH-bond) ratio as a measure of the hydration in collagen-based phantom media and rabbit corneas. RESULTS: Raman spectra with high signal-to-noise ratios were obtained under in vitro and in vivo conditions within a range of corneal hydration (H = 0.0-8.3 mg water/mg dry wt). The Raman intensity ratio OH/CH showed a strong correlation with the hydration of the phantom medium (R2 > 0.99) and the rabbit corneas (R2 > 0.95). A degree of reproducibility was seen in measurements performed at a specific depth within the cornea (SD = 1.2%-2.7%). Quantitatively, the spatially resolved corneal water content, as assessed with our method, showed an increasing gradient from the anterior to the posterior region, with a difference of approximately 0.9. Significant qualitative differences in the axial hydration gradient were observed between the in vitro and in vivo situation, caused by the presence of an intact tear-film in vivo. Characterization of the axial corneal hydration using Raman spectroscopy provided a reliable estimation of total corneal hydration compared with conventional measurements using pachymetry and lyophilization. CONCLUSIONS: The proposed noninvasive confocal Raman spectroscopic technique has the potential to assess the axial corneal water gradient with a degree of sensitivity and reproducibility.
PURPOSE: The feasibility of Raman spectroscopy for the noninvasive assessment of axial corneal hydration was investigated. METHODS: A scanning confocal Raman spectroscopy system, with an axial resolution of 50 microns, was used to assess noninvasively the water (OH-bond) to protein (CH-bond) ratio as a measure of the hydration in collagen-based phantom media and rabbit corneas. RESULTS: Raman spectra with high signal-to-noise ratios were obtained under in vitro and in vivo conditions within a range of corneal hydration (H = 0.0-8.3 mg water/mg dry wt). The Raman intensity ratio OH/CH showed a strong correlation with the hydration of the phantom medium (R2 > 0.99) and the rabbit corneas (R2 > 0.95). A degree of reproducibility was seen in measurements performed at a specific depth within the cornea (SD = 1.2%-2.7%). Quantitatively, the spatially resolved corneal water content, as assessed with our method, showed an increasing gradient from the anterior to the posterior region, with a difference of approximately 0.9. Significant qualitative differences in the axial hydration gradient were observed between the in vitro and in vivo situation, caused by the presence of an intact tear-film in vivo. Characterization of the axial corneal hydration using Raman spectroscopy provided a reliable estimation of total corneal hydration compared with conventional measurements using pachymetry and lyophilization. CONCLUSIONS: The proposed noninvasive confocal Raman spectroscopic technique has the potential to assess the axial corneal water gradient with a degree of sensitivity and reproducibility.
Authors: David B Bennett; Zachary D Taylor; Pria Tewari; Rahul S Singh; Martin O Culjat; Warren S Grundfest; Daniel J Sassoon; R Duncan Johnson; Jean-Pierre Hubschman; Elliott R Brown Journal: J Biomed Opt Date: 2011-05 Impact factor: 3.170
Authors: Andrew Chen; Omar B Osman; Zachery B Harris; Azin Abazri; Robert Honkanen; M Hassan Arbab Journal: Biomed Opt Express Date: 2020-02-07 Impact factor: 3.732
Authors: Zachary D Taylor; James Garritano; Shijun Sung; Neha Bajwa; David B Bennett; Bryan Nowroozi; Priyamvada Tewari; James Sayre; Jean-Pierre Hubschman; Sophie Deng; Elliott R Brown; Warren S Grundfest Journal: IEEE Trans Terahertz Sci Technol Date: 2015-03 Impact factor: 3.274