Abstract
The organization of fibrillar tissue on the micrometer scale carries direct implications for health and disease but remains difficult to assess in vivo. Polarization-sensitive optical coherence tomography measures birefringence, which relates to the microscopic arrangement of fibrillar tissue components. Here, we demonstrate a critical improvement in leveraging this contrast mechanism by employing the improved spatial resolution of focus-extended optical coherence microscopy (1.4 µm axially in air and 1.6 µm laterally, over more than 70 µm depth of field). Vectorial birefringence imaging of sheep cornea ex vivo reveals its lamellar organization into thin sections with distinct local optic axis orientations, paving the way to resolving similar features in vivo.
Highlights
Fibrillar collagen is the main structural extracellular matrix protein in mammals and an essential component of connective tissues
One prominent example of need is the arrangement of collagen fibers in the cornea, which provides both mechanical protection of the eye and the optical transparency required for visual acuity [1]
The polarizer filtered the unpolarized source light to a linear state oriented at 45° to the optic axis of the EOM, which was driven to operate as a quarter-waveplate with alternating positive and negative retardation
Summary
Fibrillar collagen is the main structural extracellular matrix protein in mammals and an essential component of connective tissues. The microscopic organization of collagen fibers directly impacts the mechanical and structural tissue properties. One prominent example of need is the arrangement of collagen fibers in the cornea, which provides both mechanical protection of the eye and the optical transparency required for visual acuity [1]. High-resolution microscopy, including scanning electron microscopy [2,3] and X-ray scattering [4,5] of histological sample preparations, has been used to study collagen morphology in the cornea in great detail. Rather than directly visualizing tissue microstructure, it probes the mechanical properties of the sample through measurements of the local longitudinal elastic modulus [13,14]
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