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Purpose: The lamina cribrosa (LC) is hypothesized to be the site of initial axonal damage in glaucoma with the circumpapillary retinal nerve fiber layer thickness (RNFL-T) widely used as a standard metric for quantifying the glaucomatous damage. The purpose of this study was to determine in vivo, 3-dimensional (3D) differences in the microstructure of the LC in eyes of nonhuman primates (NHPs) with naturally occurring glaucoma., Methods: Spectral-domain optical coherence tomography (OCT) scans (Leica, Chicago, IL, USA) of the optic nerve head were acquired from a colony of 50 adult rhesus monkeys suspected of having high prevalence of glaucoma. The RNFL-T was analyzed globally and in quadrants using a semi-automated segmentation software. From a set of 100 eyes, 18 eyes with the thinnest global RNFL-T were selected as the study group and 18 eyes with RNFL-T values around the 50th percentile were used as controls. A previously described automated segmentation algorithm was used for LC microstructure analysis. Parameters included beam thickness, pore diameter and their ratio (beam-to-pore ratio [BPR]), pore area and shape parameters, beam and pore volume, and connective tissue volume fraction (CTVF; beam volume/total volume). The LC microstructure was analyzed globally and in the following volumetric sectors: quadrants, central and peripheral lamina, and three depth slabs (anterior, middle, and posterior)., Results: Although no significant difference was detected between groups for age, weight, or disc size, the study group had significantly thinner RNFL than the control group (P < 0.01). The study group had significantly smaller global and sectoral pore diameter and larger BPR compared with the control group. Across eyes, the global RNFL-T was associated positively with pore diameter globally. BPR and CTVF were significantly and negatively associated with the corresponding RNFL-T in the superior quadrant., Conclusions: Global and sectoral microstructural differences were detected when comparing thin and normal RNFL-T eyes. Whether these LC differences are the cause of RNFL damage or the result of remodeling of the LC requires further investigation., Translational Relevance: Our findings indicate structural alterations in the LC of NHP exhibiting natural thinning of the RNFL, a common characteristic of glaucomatous damage.

Purpose: Lamina cribrosa (LC) deformation is hypothesized to play a major role in glaucoma pathogenesis. The purpose of this study was to determine in vivo how varying intraocular pressure (IOP) under fixed intracranial pressure (ICP), and vice versa, deforms the pore paths throughout the LC volume., Methods: Spectral-domain optical coherence tomography scans of the optic nerve head were acquired from healthy adult rhesus monkeys under different pressures. IOP and ICP were controlled with gravity-based perfusion systems into the anterior chamber and lateral ventricle, respectively. IOP and ICP were modulated from baseline to high (19-30 mmHg) and highest (35-50 mmHg) levels while maintaining a fixed ICP of 8 to 12 mmHg and IOP of 15 mmHg, respectively. After three-dimensional registration and segmentation, the paths of pores visible in all settings were tracked based on their geometric centroids. Pore path tortuosity was defined as the measured distance divided by the minimal distance between the most anterior and posterior centroids., Results: The median pore tortuosity at baseline varied among the eyes (range, 1.16-1.68). For the IOP effect under fixed ICP (six eyes, five animals), two eyes showed statistically significant increased tortuosity and one showed a decrease (P < 0.05, mixed-effects model). No significant change was detected in three eyes. When modulating ICP under fixed IOP (five eyes, four animals), a similar response pattern was detected., Conclusions: Baseline pore tortuosity and the response to acute pressure increase vary substantially across eyes., Translational Relevance: LC pore path tortuosity could be associated with glaucoma susceptibility.

Segmentation of retinal anatomical features such as optic nerve head (ONH) and optic cup, the brightest area in the center of ONH which is devoid of neural elements, is a prerequisite for computer-aided diagnosis and follow-up of glaucoma. The ONH segmentation methods, which imposed shape and intensity constraints, are unable to identify ONH and optic cup boundaries at the same time. On the other hand, recent efficient supervised learning-based methods, which provide a unified system, require combination of many informative features as their inputs, as well as ground truth for the training phase. This paper uses a saliency map including color, intensity and orientation contrasts as the input of a winner-take-all neural network, and color visual features as the input of a self-organizing map neural network to segment ONH and optic cup, simultaneously. Our method is evaluated on a database of 205 ocular fundus images provided by local eye hospitals and publicly available image databases RIMONE and DIARETDB0 comprising 60 non-glaucomtous and 145 glaucomatous images. The ground truth is provided by two expert ophthalmologists. The method attained an average overlapping error of 9.6% and 25.1% for ONH and cup segmentation, respectively. Cup-to-disc area ratio (CDR) is computed for glaucoma assessment. The mean and standard deviation of the CDR differences between our method and the ground truth in all images are 0.11 and 0.09, respectively.