Optic Nerve Head Morphometrics
Glaucoma is the second leading cause of blindness in the world with irrevocable loss of vision due to damaged retinal cells. The main risk factor in glaucoma is increase intraocular pressure (IOP), and it has been suggested that structural degradation in the optic nerve head (ONH) region due to IOP is a critical event in the progression of the disease.
Optic Nerve Head
Optic nerve head (ONH) is the region in the posterior section of the eye where the retinal nerve fibers exit the globe toward the visual cortex of the brain. The axons are subject to various mechanical tensions and torsions, and a function of the ONH is to provide mechanical support for the axons in the presence of the IOP and cerebrospinal fluid pressure (CSF).
Optical coherence tomography (OCT) enables in-vivo, 3D imaging of the ONH. The morphology of the ONH is an important indication of the structural change it goes through under various conditions, including glaucoma. In order to take full advantage of the rich information in 3D OCT, and perform comprehnsive quantitative shape analysis, an automated and robust morphometrics framework is required.
To understand the combined effect of glaucoma, myopia, and aging on the ONH, we imaged glaucoma patients and healthy controls with varying degrees of myopia and in different age groups. The acquired images were enhanced, segmented for key structures such as the retinal nerve fiber layer (RNFL), choroid, and Bruch's membrane opening (BMO), and measurements including the layer thickness, degree of surface bowing, and BMO dimension were made automatically. Mutliple regression was used to identify correlation between the shape parameters and the independent variables of age, degree of myopia, and severity of glaucoma.
S. Lee, S. Han, M. Young, M. V. Sarunic, M. F. Beg, P. J. Mackenzie, "Optic nerve head peripapillary morphometrics in myopic glaucoma," Invest. Ophthalmol. Vis. Sci., 55(7):4378-93, 2014.