Polarization microscopy for characterizing fiber orientation of ocular tissues.

Characterizing the collagen fiber orientation and organization in the eye is necessary for a complete understanding of ocular biomechanics. In this study, we assess the performance of polarized light microscopy to determine collagen fiber orientation of ocular tissues. Our results demonstrate that the method provides objective, accurate, repeatable and robust data on fiber orientation with µm-scale resolution over a broad, cm-scale, field of view, unaffected by formalin fixation, without requiring tissue dehydration, labeling or staining.

Eye-specific IOP-induced displacements and deformations of human lamina cribrosa.

Purpose: To measure high-resolution eye-specific displacements and deformations induced within the human LC microstructure by an acute increase in IOP.

Methods: Six eyes from donors aged 23 to 82 were scanned using second harmonic-generated (SHG) imaging at various levels of IOP from 10 to 50 mm Hg. An image registration technique was developed, tested, and used to find the deformation mapping between maximum intensity projection images acquired at low and elevated IOP.

High dynamic range imaging concept-based signal enhancement method reduced the optical coherence tomography measurement variability.

Purpose: To develop and test a novel signal enhancement method for optical coherence tomography (OCT) images based on the high dynamic range (HDR) imaging concept.

Methods: Three virtual channels, which represent low, medium, and high signal components, were produced for each OCT signal dataset. The dynamic range of each signal component was normalized to the full gray scale range.

A few good responses: which mechanical effects of IOP on the ONH to study?

Purpose: The biomechanical effects of IOP on the optic nerve head (ONH) are believed to play a role in glaucomatous neuropathy. There is, however, no consensus on which effects of IOP should be prioritized for investigation. Our goal was to identify a small set of variables capturing the majority of the effects of acute IOP on the ONH.

The optic nerve head as a robust biomechanical system.

Purpose. Understanding the effects of IOP on the optic nerve head (ONH) is important in understanding glaucoma and ONH structure and function. The authors tested the hypothesis that the ONH is a robust biomechanical structure wherein various factors combine to produce a relatively stable response to IOP.

IOP-induced lamina cribrosa deformation and scleral canal expansion: independent or related?

Purpose: To study the association between the intraocular pressure (IOP)-induced anterior-posterior lamina cribrosa deformation (LCD) and scleral canal expansion (SCE).

Methods: 3D eye-specific models of the lamina and sclera of the eyes of three normal monkeys were constructed. Morphing techniques were used to produce 768 models with controlled variations in geometry and materials.

Comparison of clinical and spectral domain optical coherence tomography optic disc margin anatomy.

Purpose: To investigate spectral domain optical coherence tomography (SD-OCT)-detected optic disc margin anatomy in the monkey eye by colocalizing disc photographs to SD-OCT scans acquired from the same eyes.

Methods: The neural canal opening (NCO) was delineated within 40 digital radial sections generated from SD-OCT volumes acquired from 33 normal monkey eyes (15 degrees, 290 x 768 horizontal grid pattern). Each volume was colocalized to its disc photograph by matching the retinal vessels within each photograph to vessel outlines visible within en face SD-OCT images.

The effect of acute intraocular pressure elevation on peripapillary retinal thickness, retinal nerve fiber layer thickness, and retardance.

Purpose: To determine whether acutely elevated intraocular pressure (IOP) alters peripapillary retinal thickness, retinal nerve fiber layer thickness (RNFLT), or retardance.

Methods: Nine adult nonhuman primates were studied while under isoflurane anesthesia. Retinal and RNFLTs were measured by spectral domain optical coherence tomography 30 minutes after IOP was set to 10 mm Hg and 60 minutes after IOP was set to 45 mm Hg.