Purpose:
X-ray phase-contrast tomography employs the spatial distribution of a sample’s refractive index to augment or replace conventional absorption in x-ray radiography. Planar in-line phase-contrast imaging is a Gabor holography technique that uses a highly coherent x-ray wavefield and significant post-sample propagation distances to generate interference effects at tissue discontinuities. As the in-line imaging derives contrast from refractive index boundaries, the air-tissue interface produces an effective contrast medium. The purpose of this study was to determine if x-ray phase-contrast could be effectively used to examine the 3-dimensional complexity of critical point dried ocular structures (the lens, ciliary bodies and zonules).
Methods:
Eyes from baboons were surgically removed and placed into fix (2.5% glutaraldehyde in 0.12M sodium from the eye respectively at the limbus and the ora seratta. The intact lens, still suspended by the zonules and the ciliary bodies were imaged with a benchtop in-line phase-contrast tomography system consisting of a microfocus x-ray tube source, a digital x-ray camera with a custom thermoelectric cooling system, a two-axis stage for sample positioning, and a rotation stage for tomographic imaging.
Results:
X-ray phase contrast tomography of the critical point dried ocular tissue described above produced a high-resolution image of the lens suspended by a complete, intact zonular apparatus. This enabled us to create accurate 3-D volumetric renderings of critically important ocular structures responsible for accommodation.
Conclusions:
X-ray phase-contrast tomography can be effectively used to more fully comprehend how the complex 3-dimensionality of lenses, is altered during function (accommodation) and with age (presbyopia) because the very 3-dimensionality that is to be studied does not need to be compromised when preparing it for analysis as is the case with conventional techniques (thick and thin sectioning for light and transmission electron microscopy).
Keywords: microscopy: electron microscopy • anatomy • ciliary body