J. Crawford Downs

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We propose here a conceptual framework for understanding the optic nerve head (ONH) as a biomechanical structure. Basic principles of biomechanical engineering are used to propose a central role for intraocular pressure (IOP)-related stress and strain in the physiology of ONH aging and the pathophysiology of glaucomatous damage. Our paradigm suggests that(More)
The optic nerve head (ONH) is of particular interest from a biomechanical perspective because it is a weak spot within an otherwise strong corneo-scleral envelope. The lamina cribrosa provides structural and functional support to the retinal ganglion cell axons as they pass from the relatively high-pressure environment in the eye to a low-pressure region in(More)
PURPOSE To test the hypothesis that pathophysiologic deformation of the lamina cribrosa and anterior scleral canal wall underlies the onset of confocal scanning laser tomography (CSLT)-detected optic nerve head (ONH) surface change in early experimental glaucoma. METHODS Both eyes of four normal (two normal eyes) monkeys and four with early glaucoma (one(More)
PURPOSE To characterize scleral biomechanics in both eyes of eight monkeys in which chronic intraocular pressure (IOP) elevation was induced in one eye. METHODS Each posterior sclera was mounted on a pressurization apparatus, IOP was elevated from 5 to 45 mm Hg while the 3D displacements of the scleral surface were measured by speckle interferometry.(More)
PURPOSE To delineate three-dimensionally the anterior and posterior surfaces of the lamina cribrosa, scleral flange, and peripapillary sclera, to determine the position and thickness of these structures within digital three-dimensional (3-D) reconstructions of the monkey optic nerve head (ONH). METHODS The trephinated ONH and peripapillary sclera from(More)
PURPOSE To introduce a three-dimensional (3-D) histomorphometric strategy for characterizing the connective tissue (laminar) and prelaminar neural tissue (prelaminar) components of optic nerve head (ONH) cupping in one bilaterally normal monkey and three monkeys with early experimental glaucoma (EG) in one eye. METHODS Trephined ONH and peripapillary(More)
PURPOSE To characterize the trabeculated connective tissue microarchitecture of the lamina cribrosa (LC) in terms of total connective tissue volume (CTV), connective tissue volume fraction (CTVF), predominant beam orientation, and material anisotropy in monkeys with early experimental glaucoma (EG). METHODS The optic nerve heads from three monkeys with(More)
The posterior sclera likely plays an important role in the development of glaucoma, and accurate characterization of its mechanical properties is needed to understand its impact on the more delicate optic nerve head--the primary site of damage in the disease. The posterior scleral shells from both eyes of one rhesus monkey were individually mounted on a(More)
PURPOSE To assess the ability to detect the neural canal opening (NCO) and its characteristics within three-dimensional (3-D) histomorphometric and 3-D spectral domain optical coherence tomography (SD-OCT) reconstructions of the optic nerve head from nonhuman primate (NHP) eyes. METHODS NCO was delineated within 40 radial, sagittal sections of 3-D(More)
Glaucoma is a blinding diseases in which damage to the axons results in loss of retinal ganglion cells. Experimental evidence indicates that chronic intraocular pressure elevation initiates axonal insult at the level of the lamina cribrosa. The lamina cribrosa is a porous collagen structure through which the axons pass on their path from the retina to the(More)