No / We consider and compare the various different kinds of flow that may take place in the anterior chamber of a human eye. The physical mechanisms re- sponsible for causing such flows may be classified as follows: (i) buoyancy-driven flow arising from the temperature difference between the anterior surface of the cornea and the iris, (ii) flow generated by the aqueous production of the ciliary body, (iii) flow generated by the interaction between buoyancy and gravity while sleeping while sleeping in a face-up position, (iv) flow generated by phakodenesis (lens tremor), (v) flow generated by Rapid Eye Movement (REM) during sleep. Each flow is studied using a traditional fluid mechanics/asymptotic analysis ap- proach. We also assess the veracity of a hypothesis that was recently advanced [see Maurice, D.M., 1998. The Von Sallman Lecture 1996: An ophthalmological explanation of REM sleep. Exp. Eye. Res. 66, 139¿145, for details] to suggest that, contrary to previous opinion, the purpose of REM during sleep is to ensure corneal respiration in the absence of the buoyant mixing that routinely takes place due to (i) above during waking conditions.

Clinical guidelines dictate that frequent blood glucose monitoring in diabetic patients is critical towards proper management of the disease. Although, several different types of glucose monitors are now commercially available, most of these devices are invasive, thereby adversely affecting patient compliance. To this end, optical polarimetric glucose sensing through the eye has been proposed as a potential noninvasive means to aid in the control of diabetes. Arguably, the most critical and limiting factor towards successful application of such a technique is the time varying corneal birefringence due to eye motion artifact. In the first part of this research, we describe a birefringent ocular model along with a geometric ray tracing scheme to serve as a tool towards better understanding of the cornea’s birefringence properties. The simulations show that index-unmatched coupling of light is spatially limited to a smaller range when compared to index-matched situation. Polarimetric measurements on rabbits’ eyes indicate relative agreement between the modeled and experimental values of corneal birefringence. In addition, the observed rotation in the plane of polarized light for multiple wavelengths demonstrates the potential for using a dual-wavelength polarimetric approach to overcome the noise due to time-varying corneal birefringence. These results will ultimately aid in the development of an appropriate eye coupling mechanism for in vivo polarimetric glucose measurements. The latter part of the dissertation focuses on design and development of a dual wavelength optical polarimeter. The described system utilizes real-time closed-loop feedback based on proportional-integral-derivative (PID) control, which effectively reduced the time taken by the system to stabilize while minimizing the effect of motion artifact, which appears as common noise source for both the wavelengths. Glucose measurements performed in both in vitro and ex vivo conditions demonstrate the sensitivity of the current system. Finally, in vivo results in rabbits indicate that dual-wavelength polarimetry has the potential to noninvasively probe glucose through the anterior chamber of the eye.

Made available in DSpace on 2016-09-27T13:40:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-01-23. Added 1 bitstream(s) on 2016-09-27T13:45:12Z : No. of bitstreams: 1 000870463.pdf: 877740 bytes, checksum: 79b4a09d0e6fd75bfc905a39a77c9f0d (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Intracameral injection is used for treatment and anesthesia of the eye bulb and opioids are known to provide analgesia through this route. The aim of the study was to evaluate the viability and efficacy of intracameral nalbuphine and morphine in dogs. Seven beagle dogs were randomly included in the groups of intracameral nalbuphine (GNIC), intracameral morphine (GMIC), intravenous nalbuphine (GNIV) and intravenous morphine (GMIV) injection of either opioid. Variables were heart rate, respiratory rate, systolic arterial pressure, subjective pain scale, Schirmer's test, pupillary diameter, intraocular pressure, fluorescein test, corneal touch threshold, number and type of local or systemic complications and duration of effect on the cornea. Time point comprised baseline (T0) and measurements every 30 minutes after drugs administration up to 240 minutes. Parametric variables were analyzed through ANOVA for repeated measures and Dunnett's test. Ordinal data were compared through Friedman's test, followed by Dunn's test. Analyses were performed by SAS and were considered significant when P<0.05. Analgesia lasted significantly longer in GNIC, whereas GMIC, GNIV and GMIV did not differ between one another. There was a significant decrease in the IOP at T30 in all groups when compared to baseline measures. As for complications, no difference was found between groups. Therefore, both nalbuphine and morphine can be used for intracameral analgesia, and nalbuphine is the preferred option due to the prolonged analgesia. / FAPESP: 2013/02162-4

Resumo:A injeção intracameral é utilizada para tratamentos e anestesias oftálmicas e os opioides podem promover analgesia por esta via. Objetivou-se avaliar a viabilidade e a eficiência do uso de nalbufina e morfina pela via intracameral em cães. Sete cães da raça beagle foram alocados aleatoriamente nos grupos nalbufina intracameral (GNIC), morfina intracameral (GMIC), nalbufina intravenoso (GNIV) e morfina intravenoso (GMIV). Os parâmetros avaliados foram frequência cardíaca e respiratória, pressão arterial sistólica, escala subjetiva de avaliação da dor, teste da lágrima de Schirmer, diâmetro pupilar, pressão intraocular, teste de tingimento pela fluoresceína, limiar de toque corneal, número e tipo de complicação local e/ou sistêmica e a duração do efeito dos opioides na córnea. Os momentos de estudo foram basal (M0) e a cada 30 minutos após a administração dos grupos até completar 240 minutos. As variáveis numéricas foram submetidas à análise de variância com medidas repetidas e as médias comparadas pelo teste de Dunnett's. As categóricas não paramétricas ordinais foram comparadas pelo teste de Friedman com pós-teste de Dunn. As análises foram efetuadas empregando-se o programa SAS e foram consideradas significativas quando P < 0,05. A duração da analgesia foi significativamente maior no GNIC, enquanto GMIC, GNIV e GMIV não diferiram entre si. Houve redução significativa da PIO em M30 em todos os grupos quando comparado ao M0. Quanto ao número de complicações não houve diferença significativa entre os grupos. Portanto, tanto a nalbufina quanto a morfina são viáveis pela via intracameral sendo a nalbufina mais indicada pela maior duração de seu efeito analgésico. / Abstract:Intracameral injection is used for treatment and anesthesia of the eye bulb and opioids are known to provide analgesia through this route. The aim of the study was to evaluate the viability and efficacy of intracameral nalbuphine and morphine in dogs. Seven beagle dogs were randomly included in the groups of intracameral nalbuphine (GNIC), intracameral morphine (GMIC), intravenous nalbuphine (GNIV) and intravenous morphine (GMIV) injection of either opioid. Variables were heart rate, respiratory rate, systolic arterial pressure, subjective pain scale, Schirmer's test, pupillary diameter, intraocular pressure, fluorescein test, corneal touch threshold, number and type of local or systemic complications and duration of effect on the cornea. Time point comprised baseline (T0) and measurements every 30 minutes after drugs administration up to 240 minutes. Parametric variables were analyzed through ANOVA for repeated measures and Dunnett's test. Ordinal data were compared through Friedman's test, followed by Dunn's test. Analyses were performed by SAS and were considered significant when P<0.05. Analgesia lasted significantly longer in GNIC, whereas GMIC, GNIV and GMIV did not differ between one another. There was a significant decrease in the IOP at T30 in all groups when compared to baseline measures. As for complications, no difference was found between groups. Therefore, both nalbuphine and morphine can be used for intracameral analgesia, and nalbuphine is the preferred option due to the prolonged analgesia. / Orientador:Valéria Nobre Leal de Souza Oliva / Banca:Lídia Mitsuko Matsubara / Banca:Flavia de Almeida Lucas / Banca:Alexandre Lima de Andrade / Banca:Celina Tie Duque Nishimori / Doutor

We illustrate here how a range of fluid and solid mechanics problems relevant to the human eye have been combined in a continuing PhD study. Anterior chamber flow, the solid mechanics of tonometry, the effects of scleral buckle surgery and the mechanics of retinal detachment are all discussed. Finally, a number of other aye problems that are amenable to a theoretical mechanics treatment are proposed.

Yes / Purpose: To determine whether human ocular lens position is influenced by gravity. Methods: Anterior chamber depth and lens thickness were determined with a Haag-Streit Lenstar LS900 for right eyes of participants in two age groups, with a young group of 13 participants aged 18 to 21 years (mean 21 years, SD 1 year) and an older group of 10 participants aged 50 to 63 years (58 years, 4 years). There were two sessions for each participant separated by at least 48 hours, with one session for the usual upright head position and one session for a downwards head position. In a session, testing was done for minimum accommodation followed by testing at maximum accommodation. A drop of 2% pilocarpine nitrate was instilled, and testing was repeated after 30 minutes under minimum and maximum accommodation conditions. Results: Gravity, manipulated through head posture, affected anterior chamber depth for both young adult and older adult groups but mean effects were only small, ranging from 0.04 to 0.12mm, and for the older group required the instillation of an accommodation-stimulating drug. Gravity had a weakly significant effect on lens thickness for the young group without accommodation or a drug, but the effect was small at 0.04±0.06mm (mean±SD, p = 0.04). Conclusion: There is a small but real effect of gravity on crystalline lens position, manifested as reduction in anterior chamber depth at high levels of accommodative effort with the head in a downwards position. This provides evidence of the ability of zonules to slacken during strong accommodation.

Estima-se que, em 2013, cerca de 382 milhões de pessoas eram portadoras de diabetes mundialmente. Já o diabetes mellitus do tipo 1 (DMT1) representa de 5-10% desse total de casos, cujo tratamento atual se pauta na administração de insulina exógena. Contudo, desde a publicação do protocolo de Edmonton, o transplante de ilhotas pancreáticas se apresenta como nova técnica no tratamento para o DMT1, inclusive obtendo a independência de insulina em alguns casos. Apesar disso, a escolha do sítio receptor ainda é essencial para diminuir efeitos adversos e permitir o acompanhamento do enxerto. Nesse sentido, destaca-se o transplante de ilhotas para a câmara anterior do olho, pois permite, além do restabelecimento do controle glicêmico, o estudo da fisiologia dos enxertos in vivo. Dessa forma, o objetivo foi estabelecer metodologia de isolamento e transplante de ilhotas de alta reprodutibilidade e baixo custo, utilizando a câmara anterior do olho como sítio receptor. O isolamento foi realizado via injeção de solução de colagenase (1 mg/mL via ducto colédoco) em camundongos machos C57BL/6 hígidos de 8 semanas de idade e posterior transplante dessas ilhotas para camundongos machos da mesma espécie com diabetes induzido por injeção de aloxana (60 mg/kg, i.v.). Esses camundongos foram submetidos a infusão de aproximadamente 250 equivalentes de ilhotas (IEQs) para a câmara anterior do olho e tiveram sua glicemia e alteração de massa corpórea acompanhadas por 14 dias após o transplante. Também foi realizado teste de tolerância a glicose via injeção de solução de glicose (2g/kg i.p.) e realização da curva glicêmica. Obteve-se, na etapa de padronização, que a adição de 0,5% (%p/v) de albumina de soro bovino à solução de colagenase foi capaz de aumentar o número de IEQs isolados por animal. Quanto ao transplante, obteve-se que 50% dos animais submetidos à técnica tiveram diminuição significativa na sua glicemia (172,5 ± 6,4 mg/dL), quando comparados com o grupo controle diabético (582,8 ± 27,5 mg/dL) (p < 0,05). Entretanto, todos os animais tiveram aumento significativo da massa corpórea no período de acompanhamento e glicemia de jejum significativamente menor que os animais diabéticos (p < 0,05). Ademais, a curva glicêmica dos animais que tiveram transplante considerado bem sucedido, no teste de tolerância a glicose, se aproxima da curva do grupo controle sadio. Conclui-se que o modelo de transplante de ilhotas pancreáticas para a câmara anterior do olho foi bem estabelecido neste projeto, confirmado pelos resultados que evidenciam o transplante de ilhotas funcionais capazes de reduzir sensivelmente a glicemia e promover o ganho de peso em camundongos diabéticos. / It is estimated that, in 2013, around 382 million people had diabetes worldwide. Of that number, 5-10% represented cases of T1DM, which treatment is based in the administration of exogenous insulin. However, since the Edmonton protocol was published, islet transplantation presented itself as novel technique for T1DM treatment, achieving insulin independence in some cases. Although, recipient site choice is still essential to diminish side effects and enable graft follow up. In that sense, transplantation to the anterior chamber of the eye stands out, since it allows, beyond the reestablishment of glycemic control, study of islet physiology in vivo. That way, the objective was to establish a low cost and high reproducible model of islet isolation and transplantation, using the anterior chamber of the eye as receptor site. Islet isolation was made by injection of collagenase solution (1 mg/mL via common bile duct) in 8 week old healthy male C57BL/6 mice and followed by transplantation of these islets to male mice of the same age and species with diabetes induced by alloxan injection (60 mg/kg i.v.). These mice were subject of 250 islet equivalents (IEQs) infusion to the anterior chamber of the eye and had their blood glucose and change in body mass monitored for 14 days after transplantation. A glucose tolerance test (GTT) was also made, by injection of glucose solution (2g/kg i.p.) and a glycemic curve was plotted. In the standardization period, was observed that the addition of 0,5% (%w/v) bovine serum albumin is capable of increasing the number of IEQs isolated from each animal. About the transplants, was obtained that 50% of animals subject to transplantation had their blood glucose decreased significantly (172,5 ± 6,4 mg/dL), when compared to the diabetic control group (582,8 ± 27,5 mg/dL) (p < 0,05). However, all animals subject to the procedure had significant body mass increase, when compared to the same control group and fasting blood glucose significantly lower than diabetic animals (p < 0,05). Moreover, the glycemic curve of animals, who had their transplantation considered successful, was similar to that found in healthy control animals, in the GTT. We conclude that the model of transplant to the anterior chamber of the eye is well established in this project, which is confirmed by results that shows transplantation of functional islets, capable of promoting a significant decrease in blood glucose and an increase in total body mass in diabetic animals.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 138-153).

Purpose: The aim of the present study was to compare and investigate morphometric characteristics of limbal vasculature within the superior and inferior limbal regions using ultra-high resolution optical coherence tomography. Method: Cross-sectional images of the human corneo-scleral limbus were acquired with a research grade ultra-high resolution optical coherence tomographer (UHR-OCT) from 14 healthy subjects after manual retraction of the upper and lower eyelid. The UHR-OCT provides an axial and lateral resolution in biological tissue of ~3μm and ~18μm, respectively. 3D stacks of OCT images (1000 x 1024 x 256) were acquired of the transition from cornea to bulbar conjunctiva at the superior and inferior limbal region. All visible vessels within the limbal region were measured using an Image J circle or ellipse tool. Vessel depth and size measurements were repeated for the same vessel and the concordance correlation coefficient was computed. Quantitative differences in vessel size and depth in the limbal region were analyzed using repeated measured ANOVA. R and SPSS were used for all data analysis procedures. Results: The average vessel size for superior and inferior limbus were 29.28µm ± 17.649 µm (SD) and 23.68µm ± 18.118µm (SD) respectively. The average vessel depth for superior and inferior limbus were 176.76µm ± 108.698µm (SD) and 205.62µm ± 131.991µm (SD) respectively. The concordance correlation coefficient for superior and inferior limbal vessel size were 0.95 (95% CI, 0.935 to 0.964) and 0.994 (95% CI, 0.991 to 0.995) respectively, while that of vessel depth were 0.998 (95% CI, 0.997 to 0.999) and 0.998 (95% CI, 0.997 to 0.998) respectively. The vessels within the superior limbus were larger than the vessels found in the inferior limbus (RM-ANOVA POS p = 0.004), and the vessels within the inferior limbus were on average deeper than the vessels found within the superior limbus (RM-ANOVA POS p = 0.042). There was a positive linear relationship between limbal vessel depth and size within the superior and inferior limbus with a Pearson correlation coefficient of 0.803 and 0.754, respectively. There were on average 9 vessels per subject within the superior limbal region as compared to 13 vessels per subject with the inferior limbal region. Conclusion: This study provided evidence that the UHR-OCT was capable of imaging (and therefore measuring) morphometric characteristics such as the size and depth of vessels within the limbus in a repeatable manner. A positive linear association between vessel depth and size was identified in the superior and inferior limbal regions. The results of this study suggest a definite difference in the size and depth of vessels across different positions of the limbus, and this may be indicative of adaptations to chronic hypoxia caused by the constant covering of the superior limbus by the upper eyelid.

Thesis (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2006. / Embargoed. Vita. Bibliography: 117-136.