Purchase this article with an account.
Ilyas Saytashev, Natalia Lopez, Joseph Chue-Sang, Jessica Ramella-Roman; Simultaneous second harmonic generation and Mueller Matrix polarimetry imaging of the rat cornea. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5844.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Polarimetry has shown great potential in achieving a deeper understanding of structural and biochemical changes in the eye. For example, polarimetry has been used for monitoring collagen changes due to keratoconus in the cornea and for non-invasive measurements of glucose level for diabetic patients. The development of quantitative polarimetric instrumentation presents a challenge due to the required precision and scale. Validation of polarimetric images is complicated by the lack of optical standards and by the heterogeneity of the underlying tissue. We propose the use of SHG as a gold standard for validating MMP imagery. A combined MMP/SHG system is at the core of this research.
The combined nonlinear and MMP imaging setup is shown in figure 1. A home-built laser scanning microscope with two detection channels was modified with the addition of a polarization state generator (PSG), polarization state analyzer (PSA) and CCD camera. 16 different images were necessary to reconstruct the Mueller Matrix.Rat corneas were obtained from old Long-Evans male rats, and mounted between on a glass slide. Images were obtained from different regions of the cornea.
Collagen fiber orientation, which defines the birefringence in the tissue, can be clearly visualized via SHG imaging (Fig. 2). Orientation angles of a fast axis in the birefringent cornea generally co-aligned with collagen fiber orientation.
Depth-resolved SHG imaging provided 3D reconstruction of collagen distribution, while MM decomposition allowed us to map diattenuation, linear retardation and orientation of imaged area. We demonstrated co-registered linear (MMP) and nonlinear (SHG) imaging modalities in excised rat cornea, and directly compared polarization properties of the rat cornea with its fibrillar collagen microsctructure.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Schematic diagram of co-registered nonlinear and MMP laser scanning microscope. A pair of liquid crystal variable retarders (LCVR1 and LCVR2) deliver four polarization states calibrated at the focal point of an objective; a fraction of reflected light from a sample is attenuated (ND), filtered (BP filter), analyzed by another pair of liquid crystal variable retarders (LCVR3 and LCVR4) with polarizer, and acquired by a CCD camera.
Top: SHG image of a rat cornea. Middle: orientation map, obtained after decomposition of MM. Bottom: overlay image of orientation (quiver plot) and SHG imagery.
This PDF is available to Subscribers Only