Indiana University-Purdue University Indianapolis (IUPUI) / The vein structure in the sclera, the white and opaque outer protective covering of the eye, is anecdotally stable over time and unique to each person. As a result, it is well suited for use as a biometric for human identification. A few researchers have performed sclera vein pattern recognition and have reported promising, but low accuracy, initial results. Sclera recognition poses several challenges: the vein structure moves and deforms with the movement of the eye and its surrounding tissues; images of sclera patterns are often defocused and/or saturated; and, most importantly, the vein structure in the sclera is multi-layered and has complex non-linear deformation. The previous approaches in sclera recognition have treated the sclera patterns as a one-layered vein structure, and, as a result, their sclera recognition accuracy is not high. In this thesis, we propose a new method for sclera recognition with the following contributions: First, we developed a color-based sclera region estimation scheme for sclera segmentation. Second, we designed a Gabor wavelet based sclera pattern enhancement method, and an adaptive thresholding method to emphasize and binarize the sclera vein patterns. Third, we proposed a line descriptor based feature extraction, registration, and matching method that is scale-, orientation-, and deformation-invariant, and can mitigate the multi-layered deformation effects and tolerate segmentation error. It is empirically verified using the UBIRIS and IUPUI multi-wavelength databases that the proposed method can perform accurate sclera recognition. In addition, the recognition results are compared to iris recognition algorithms, with very comparable results.

Lic.-avh. (sammanfattning) Stockholm : Karol. inst., 2006. / Härtill 2 uppsatser.

PURPOSE. The purpose of this study was to quantify the biomechanical response of human posterior ocular tissues from donors of various racioethnic groups to better understand how differences in these properties may play a role in the racioethnic health disparities known to exist in glaucoma. METHODS. Sequential digital image correlation (S-DIC) was used to measure the pressure-induced surface deformations of 23 normal human posterior poles from three racioethnic groups: African descent (AD), European descent (ED), and Hispanic ethnicity (HIS). Regional in-plane principal strains were compared across three zones: the optic nerve stump (ONS), the peripapillary (PP) sclera, and non-PP sclera. RESULTS. The PP scleral tensile strains were found to be lower for ED eyes compared with AD and HIS eyes at 15 mm Hg (P = 0.024 and 0.039, respectively). The mean compressive strains were significantly higher for AD eyes compared with ED eyes at 15 mm Hg (P = 0.018). We also found that the relationship between tensile strain and pressure was significant for those of ED and HIS eyes (P < 0.001 and P = 0.004, respectively), whereas it was not significant for those of AD (P = 0.392). CONCLUSIONS. Our results suggest that, assuming glaucomatous nerve loss is caused by mechanical strains in the vicinity of the optic nerve head, the mechanism of increased glaucoma prevalence may be different in those of AD versus HIS. Our ONS strain analysis also suggested that it may be important to account for ONS geometry and material properties in future scleral biomechanical analysis.

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2007. / Committee Chair: Prausnitz, Mark R.; Committee Member: Allen, Mark; Committee Member: Edelhauser, Henry; Committee Member: Geroski, Dayle; Committee Member: Nickerson, John; Committee Member: Sambanis, Athanassios.

As is the case with many ocular neuropathies, primary open-angle glaucoma (POAG) leads to an irreversible damage to the visual field. Loss of visual field first occurs in the peripheral vision and slowly propagates towards the middle. Although there are differences in its rate of incidence, glaucoma is projected to be the leading cause of blindness, second only to cataract, affecting significant percentage of populations across different age, race/ethnic groups. A hallmark of POAG is the dysfunction of retinal ganglion cells (RGCs) which connect to the axons which, in turn, relay the visual information from the eye to the brain. Previous research has shown that axonal density in the optic nerve head (ONH) is greatly reduced due to chronically elevated intraocular pressure (IOP). IOP-lowering treatment has been shown to reduce the visual field loss, and continues to be the dominant treatment methodology for glaucoma. Previous research has shown that the biomechanics of the lamina cribrosa (LC) - a highly porous tissue through which the axons carrying the visual information exit the eye, is important in influencing the viability of the RGCs. In a normal eye, the LC is primarily made up of collagen of types I, III, and IV which encompass (specifically, arranged circularly) the axon shafts and the blood vessels (1). In addition to elevated IOP, changes in the material properties of ocular tissues in and around the ONH region, which include peripapillary sclera and LC, could affect its biomechanics, which could be a result of changing microstructure and morphology of these tissues, and may contribute to POAG. The current work is aimed at creating computational models to incorporate the complex nature of ocular tissues, and develop computational techniques to characterize the variation in the material properties of ocular tissues (which include the tissue moduli, fiber orientation, permeability etc.), and study the effects they have on the biomechanical response of the LC region.

Blindness due to ocular trauma is a significant problem in the United States considering that each year approximately 500,000 years of eyesight are lost. The most likely sources of eye injuries include sports related impacts, automobile accidents, consumer products, and military combat. Out of the 1.9 million total eye injuries in the country, more than 600,000 sports injuries occur each year and 40,000 of them require emergency care. In 2007, approximately 66,000 people suffered from vehicle related eye injuries in the United States. Of the vehicle occupants sustaining an eye injury during a crash, as many as 15% to 25% sustained severe eye injuries and it was shown that within these severe eye injuries as many as 45% resulted in globe rupture. The purpose of this thesis is to characterize the biomechanical response of the human eye to dynamic loading. A number of test series were conducted with different loading conditions to gather data. A drop tower pressurization system was used to dynamically increase intraocular pressure until rupture. Results for rupture pressure, stress and strain were reported. Water streams that varied in diameter and velocity were developed using a customized pressure system to impact eyes. Intraocular pressure, normalized energy and eye injury risk were reported. A Facial and Ocular Countermeasure Safety (FOCUS) headform was used to measure the force applied to a synthetic eye during each hit from projectile shooting toys. The risk of eye injury for each impact was reported. These data provide new and significant research to the field of eye injury biomechanics to further the understanding of eye injury thresholds. / Master of Science

Baseados no fato de que o corpo escleral sofre alterações progressivas de sua cor no decorrer do tempo, e também pela ausência na literatura específica de trabalhos experimentais relacionados com estas alterações, o presente trabalho tem por objetivo, verificar o desempenho de resinas para esclera e de três tipos de pigmentos neste processo. Os pigmentos utilizados para este fim foram: lápis aquarelável, acrílico termo-polimerizante colorido e pigmento cerâmico; nas cores azul, amarelo e vermelho. Para a realização do experimento, foram confeccionados 100 corpos de prova, sendo 50 de resina para esclera no1e os outros 50 de resina para esclera no2. Cada grupo foi subdividido em 10 subgrupos, com 5 unidades cada, separados em quatro categorias: A, B ,C e E. O grupo A foi caracterizado com lápis aquarelável, o B com resina termo-polimerizável colorida, o C com pigmento cerâmico e o E não recebeu caracterização. Todos os grupos foram recobertos por uma camada de resina incolor. Inicialmente, todos os corpos de prova foram submetidos à análise em um espectrofotômetro acoplado a um sistema de colorimetria. A leitura inicial foi considerada como padrão, sendo as demais, efetuadas a cada 24 horas, até um total de 144 horas intercaladas com ensaios de envelhecimento acelerado por radiação UVA. Os dados colorimétricos, obtidos através das curvas de reflexão de cada amostra, foram utilizados para o cálculo das diferenças de cor. Após o tratamento estatístico dos dados obtidos, foi possível concluir que o lápis aquarelável, nas cores amarela e vermelha e o pigmento cerâmico vermelho, apresentaram uma estabilidade de cor clinicamente aceitável durante todo o tempo experimental. Das duas resinas para esclera avaliadas, a de no2 apresentou melhor estabilidade de cor. / Based on the fact that the sclera of ocular prosthesis presents progressive color alterations with time and due to lack of experimental studies on this topic, the purpose of this study was to evaluate the performance of two types of resins combined with three different kinds of pigments. The pigments used herein were: watercolour pencils, heat-polymerized acrylic resin and ceramic pigment on the colors blue, yellow and red. A total of one-hundred specimens were prepared, among which 50 were made by resin no 1 and the remaining 50 were made by resin no 2. Each group of 50 samples were divided in 10 subgroups containing 5 specimens each, and were separated in four categories: A, B, C and E. Group A was colored with watercolour pencils, while in group B it was used heat-polymerized acrylic resin and in group C, it was used ceramic pigment. Group E was not pigmented. After pigmentation, all specimens received a transparent heat-cured resin layer. At time point zero, all specimens were assessed by a spectrophotometer connected to a colorimeter system, and the initial data were used as the standard value. Immediately after the initial assessment, all samples were kept in a UVA irradiation chamber. The following data were taken after every 24 hours until completion of 144 hours. All colorimetric data were obtained by the reflection curves of each sample and used to calculate the color difference rate. After statistical analysis, it was concluded that the samples colored with watercolour pencil in yellow and red as well as the ceramic pigment in red showed color stability clinically acceptable during the whole experimental period. Between the two types of resin used herein, the resin no 2 showed better color stability.

The research aims of this thesis are to investigate the attention cues available to and used by apes, especially gorillas (Gorilla gorilla), to ascertain the direction of conspecific attention during social interactions with a special reference to social play. Minimal research has been conducted on the role of attention cues - eye gaze, head, and body orientation - to regulate natural social interactions, such as social play, in non-human primates. This thesis begins with an investigation of the "cooperative eye hypothesis", which poses that humans have evolved a unique white sclera adaptation for advertising and detecting gaze direction. Chapter 2 reports the existence of a natural white sclera variation in a proportion of gorilla eyes - contradicting the widely held assumption that white sclera is an exclusively human characteristic - and analyzes the presence of white sclera in relation to other morphological changes in the human eye. The study concludes that the morphological elongation of the eye might be a more important and unique change than the white sclera coloration. Chapter 3 experimentally explores the contribution of white sclera in both great ape and human eye gaze to the perception of gaze direction detection by human observers. This chapter concludes that although white sclera contributes to the accuracy and speed of gaze direction detection (an assumption that this thesis has put to experimental test for the first time), this merely adds to the already efficient gaze cues available in the eye areas of the ape face. Chapter 4 investigates the role of eye gaze, head, and body orientations during gorilla social play behavior, and more specifically, introduces a novel analysis of "vigilance periods" (VPs), in which gorillas may use the interaction between attention cues to gauge the attention and intentions of play partners to successfully navigate play. The final study (Chapter 5) complements Chapter 4 and investigates the role of gorilla postures, behaviors, and movements during changes in attentional cue orientations. This chapter concludes that gorillas often engage in physical rest during VPs but maintain attentional engagement and can assemble and impart socially relevant information based on the behaviors, movements, and attention orientations of their partner. Together, these studies suggest that attention orientation is conveyed and assessed by gorillas through a variety of interacting cues to navigate and modify social play interactions.

Baseados no fato de que o corpo escleral sofre alterações progressivas de sua cor no decorrer do tempo, e também pela ausência na literatura específica de trabalhos experimentais relacionados com estas alterações, o presente trabalho tem por objetivo, verificar o desempenho de resinas para esclera e de três tipos de pigmentos neste processo. Os pigmentos utilizados para este fim foram: lápis aquarelável, acrílico termo-polimerizante colorido e pigmento cerâmico; nas cores azul, amarelo e vermelho. Para a realização do experimento, foram confeccionados 100 corpos de prova, sendo 50 de resina para esclera no1e os outros 50 de resina para esclera no2. Cada grupo foi subdividido em 10 subgrupos, com 5 unidades cada, separados em quatro categorias: A, B ,C e E. O grupo A foi caracterizado com lápis aquarelável, o B com resina termo-polimerizável colorida, o C com pigmento cerâmico e o E não recebeu caracterização. Todos os grupos foram recobertos por uma camada de resina incolor. Inicialmente, todos os corpos de prova foram submetidos à análise em um espectrofotômetro acoplado a um sistema de colorimetria. A leitura inicial foi considerada como padrão, sendo as demais, efetuadas a cada 24 horas, até um total de 144 horas intercaladas com ensaios de envelhecimento acelerado por radiação UVA. Os dados colorimétricos, obtidos através das curvas de reflexão de cada amostra, foram utilizados para o cálculo das diferenças de cor. Após o tratamento estatístico dos dados obtidos, foi possível concluir que o lápis aquarelável, nas cores amarela e vermelha e o pigmento cerâmico vermelho, apresentaram uma estabilidade de cor clinicamente aceitável durante todo o tempo experimental. Das duas resinas para esclera avaliadas, a de no2 apresentou melhor estabilidade de cor. / Based on the fact that the sclera of ocular prosthesis presents progressive color alterations with time and due to lack of experimental studies on this topic, the purpose of this study was to evaluate the performance of two types of resins combined with three different kinds of pigments. The pigments used herein were: watercolour pencils, heat-polymerized acrylic resin and ceramic pigment on the colors blue, yellow and red. A total of one-hundred specimens were prepared, among which 50 were made by resin no 1 and the remaining 50 were made by resin no 2. Each group of 50 samples were divided in 10 subgroups containing 5 specimens each, and were separated in four categories: A, B, C and E. Group A was colored with watercolour pencils, while in group B it was used heat-polymerized acrylic resin and in group C, it was used ceramic pigment. Group E was not pigmented. After pigmentation, all specimens received a transparent heat-cured resin layer. At time point zero, all specimens were assessed by a spectrophotometer connected to a colorimeter system, and the initial data were used as the standard value. Immediately after the initial assessment, all samples were kept in a UVA irradiation chamber. The following data were taken after every 24 hours until completion of 144 hours. All colorimetric data were obtained by the reflection curves of each sample and used to calculate the color difference rate. After statistical analysis, it was concluded that the samples colored with watercolour pencil in yellow and red as well as the ceramic pigment in red showed color stability clinically acceptable during the whole experimental period. Between the two types of resin used herein, the resin no 2 showed better color stability.

Die Arbeit umreißt das Krankheitsbild der Myopie (Kurzsichtigkeit) und deren unterschiedliche Ausprägungen, im Speziellen der progressiven und pathologischen Myopie. Hierbei wird ein Einblick in die Symptomatik, die anatomischen Ursachen und die heutigen medizinischen Interventionen gegeben. Hierdurch wird die Problematik einer zu „weichen“ Sklera (Lederhaut des Auges) und des damit einhergehenden fortschreitenden Augenwachstums deutlich. Im Zentrum der Arbeit steht ein neuer therapeutischer Ansatz zur vorbeugenden Behandlung der pathologischen Myopie; das Riboflavin/Blaulicht Cross-Linking der Sklera des Kaninchenauges. Dessen Wirkungsweise ermöglicht die biomechanische Versteifung von kollagenem Gewebe. Aus diesem Sachverhalt ergibt sich die Fragestellung der Arbeit: Ist das sklerale Riboflavin/Blaulicht Cross Linking geeignet das Augenwachstum im Tiermodell (junge Kaninchen) verträglich zu hemmen? Operationsbeeinflussende Parameter wie die Riboflavin-Durchdringungsdauer der Sklera und die sklerale Lichtdurchlässigkeit werden untersucht und für die Optimierung der Operationsmethode herangezogen und diskutiert. Zur Einschätzung des Versuchsansatzes werden die im Methodikteil dargelegten Anwendungen an adulten und jungen Kaninchen/Kaninchenaugen durchgeführt. In Tierversuchen wird die Schadensschwelle in Abhängigkeit der Blaulichtintensität, des Alters und der Pigmentierung untersucht, wobei histologische, immunhistochemische und elektronenmikroskopische Verfahren angewendet werden. Der inhibitorische Einfluss des Riboflavin/Blaulicht Cross-Linkings auf das Augenwachstum kann im Jungtiermodell durch verschiedene metrische Verfahren und MRT-Untersuchungen belegt werden.