Knowledge of the mechanics of the lens capsule is crucial for improving cataract surgery as well as understanding better the physiological role of the lens capsule in the process of accommodation. Previous research on the mechanical properties of the lens capsule contains many gaps and contradictions due to experimental limitations and inappropriate assumptions. Thus, the goal of this work is to quantify fully the regional, multiaxial mechanical behavior of the lens capsule and to calculate the change in stress and strain fields as a result of cataract surgery. Determining in situ the multiaxial mechanical behavior of the lens capsule required the design and construction of an experimental device capable of altering stresses in the capsule while measuring localized surface deformations. Tests performed on this device reveal that the meridional and circumferential strains align with the principal directions and are equivalent through most of the anterior lens capsule, except close to the equator where the meridional strain is greater. Furthermore, preconditioning effects were also found to be significant. Most importantly, however, these tests provide the data necessary for calculating material properties. This experimental system is advantageous in that it allows reconstruction of 3D geometry of the lens capsule and thereby quantification of curvature changes, as well as measurement of surface deformations that result from various surgical interventions. For instance, a continuous circular capsulorhexis (CCC) is commonly used during cataract surgery to create a hole in the anterior lens capsule (typically with a diameter of 5 mm). After the introduction of a CCC, strain was found to redistribute evenly from the meridional direction (retractional strain) to the circumferential direction (extensional strain), where both directional components of strain reached magnitudes up to 20% near the edge of the CCC. Furthermore, the curvature was found to increase at the edge of the CCC and remain the same near the equator, indicating that the mere introduction of a hole in the lens capsule will alter the focal characteristics of the lens and must therefore be considered in the design of an accommodative intraocular lens.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 6 uppsatser.

O objetivo do estudo foi analisar a cápsula e o epitéilo subcapsular cristaliniano (ESC) de pacientes submetidos à capsulotomia curvilínea contínua (CCC) utilizando o corante azul de tripano (AT) a 0,1%, através de microscopia óptica (MO), da técnica TUNEL, de imunohistoquímica e de microscopia eletrônica transmissão (MET). Realizamos um estudo prospectivo, controlado e randomizado utilizando 30 amostras de cápsulas e ESC obtidos de pacientes após CCC durante cirurgia de facectomia. Essas amostras foram divididas em dois grupos (15 espécimes cada) um utilizando o AT (grupo experimental) no ato cirúrgico e o outro sem o uso do corante (grupo controle). As cápsulas e o ESC destes grupos foram fixados e processados para análises estruturais posteriores com técnicas de MO de rotina, técnica TUNEL para detecção de morte celular por apoptose, imunohistoquímica para analisar a expressão da beclina-1 (um marcador de morte celular por autofagia), além de análise ultraestrutural por meio da MET. Foram realizadas análises morfométricas das imagens de microscopia após captura e digitalização, utilizando o programa Image Pró Plus (Cybernetics®, USA). Foram encontrados resultados positivos para a expressão de morte celular por apoptose e por autofagia no grupo submetido ao uso do AT, enquanto que no grupo controle os resultados foram negativos. As análises através da MET do ESC mostraram alterações em células coradas com o AT, incluindo ruptura mitocondrial, dilatação das cisternas do retículo endoplasmático, aumento da elétrondensidade citoplasmática e nuclear, e alteração no perfil nuclear. Os resultados estatísticos obtidos pelo teste de Mann-Whitney a partir da morfometria obtida de micrografias, demonstraram diferenças morfológicas significativas entre os grupos estudados, tanto nas dimensões dos maiores eixos nucleares, quanto na relação perímetro/área do núcleo celular (p=0,03). Em relação à espessura da cápsula, do epitélio subcapsular e do conjunto dessas estruturas obtidas a partir da MO de rotina não houve diferença estatisticamente significativa entre os grupos (p= 0,1). O AT provoca no ESC toxicidade celular com sinais indicativos de morte celular. Observamos nos aspectos morfológicos e moleculares morte celular tanto pelo mecanismo de apoptose quanto de autofagia. A partir destes achados podemos sugerir que a ação do AT, talvez possa ajudar a prevenir ou reduzir a opacificação da cápsula posterior do cristalino no período pós-operatório das facectomias / The purpose of this study was to evaluate the effect of trypan blue (TB) 0.1% staining on lens epithelial cells (LECs) and capsules of patients undergoing capsulorhexis using routine optical microscopy (OM), TUNEL technique, immunohistochemistry and transmission electron microscopy (TEM). In a prospective controlled and randomized study we evaluated 30 samples of capsules with LECs obtained after capsulorhexis during cataract surgery. Samples were randomly assigned to one of two groups (15 specimens each), one submitted to TB (experimental group) during the surgery and the other without the dye (control group). The capsule and the LECs of both groups were fixed and processed for later structural analysis with routine optical microscopy, immunohistochemistry for beclin-1 expression (a marker of cell death by autophagy), and the TUNEL technique to detect apoptosis, in addition to ultra-structural analysis by TEM. Morphometrical analysis were performed by using the Image Pro Plus software (Cybernetics®, USA). In the TB-stained group we have found positive results for the expression of cell death by autophagy and apoptosis while in the control group the results were negative. Analysis of LEC by TEM showed abnormalities in TB-stained cells including mitochondrial disruption, dilation of the endoplasmic reticulum cisterns, increased cytoplasmic and nuclear electron density and abnormalities in the nuclear profile. Statistical analysis using the Mann-Whitney test on morphometric data from micrographies showed significant morphologic differences between the two groups, both regarding longest nuclear axis difference and the ratio between the total nuclear perimeter and the cell area (p=0.03). No statistically significant difference was observed in capsule thickness, the LEC and the grouping of these two structures obtained from routine OM (p=0.1). Trypan blue is toxic to LECs, and cause abnormalities indicative of cell death. We observed molecular and morphologic aspects of cell death both by the mechanism of apoptosis and autophagy. Our findings lend support to the hypothesis that staining with 0.1% TB can help prevent or reduce the incidence of posterior capsule opacification following cataract surgery

O objetivo do estudo foi analisar a cápsula e o epitéilo subcapsular cristaliniano (ESC) de pacientes submetidos à capsulotomia curvilínea contínua (CCC) utilizando o corante azul de tripano (AT) a 0,1%, através de microscopia óptica (MO), da técnica TUNEL, de imunohistoquímica e de microscopia eletrônica transmissão (MET). Realizamos um estudo prospectivo, controlado e randomizado utilizando 30 amostras de cápsulas e ESC obtidos de pacientes após CCC durante cirurgia de facectomia. Essas amostras foram divididas em dois grupos (15 espécimes cada) um utilizando o AT (grupo experimental) no ato cirúrgico e o outro sem o uso do corante (grupo controle). As cápsulas e o ESC destes grupos foram fixados e processados para análises estruturais posteriores com técnicas de MO de rotina, técnica TUNEL para detecção de morte celular por apoptose, imunohistoquímica para analisar a expressão da beclina-1 (um marcador de morte celular por autofagia), além de análise ultraestrutural por meio da MET. Foram realizadas análises morfométricas das imagens de microscopia após captura e digitalização, utilizando o programa Image Pró Plus (Cybernetics®, USA). Foram encontrados resultados positivos para a expressão de morte celular por apoptose e por autofagia no grupo submetido ao uso do AT, enquanto que no grupo controle os resultados foram negativos. As análises através da MET do ESC mostraram alterações em células coradas com o AT, incluindo ruptura mitocondrial, dilatação das cisternas do retículo endoplasmático, aumento da elétrondensidade citoplasmática e nuclear, e alteração no perfil nuclear. Os resultados estatísticos obtidos pelo teste de Mann-Whitney a partir da morfometria obtida de micrografias, demonstraram diferenças morfológicas significativas entre os grupos estudados, tanto nas dimensões dos maiores eixos nucleares, quanto na relação perímetro/área do núcleo celular (p=0,03). Em relação à espessura da cápsula, do epitélio subcapsular e do conjunto dessas estruturas obtidas a partir da MO de rotina não houve diferença estatisticamente significativa entre os grupos (p= 0,1). O AT provoca no ESC toxicidade celular com sinais indicativos de morte celular. Observamos nos aspectos morfológicos e moleculares morte celular tanto pelo mecanismo de apoptose quanto de autofagia. A partir destes achados podemos sugerir que a ação do AT, talvez possa ajudar a prevenir ou reduzir a opacificação da cápsula posterior do cristalino no período pós-operatório das facectomias / The purpose of this study was to evaluate the effect of trypan blue (TB) 0.1% staining on lens epithelial cells (LECs) and capsules of patients undergoing capsulorhexis using routine optical microscopy (OM), TUNEL technique, immunohistochemistry and transmission electron microscopy (TEM). In a prospective controlled and randomized study we evaluated 30 samples of capsules with LECs obtained after capsulorhexis during cataract surgery. Samples were randomly assigned to one of two groups (15 specimens each), one submitted to TB (experimental group) during the surgery and the other without the dye (control group). The capsule and the LECs of both groups were fixed and processed for later structural analysis with routine optical microscopy, immunohistochemistry for beclin-1 expression (a marker of cell death by autophagy), and the TUNEL technique to detect apoptosis, in addition to ultra-structural analysis by TEM. Morphometrical analysis were performed by using the Image Pro Plus software (Cybernetics®, USA). In the TB-stained group we have found positive results for the expression of cell death by autophagy and apoptosis while in the control group the results were negative. Analysis of LEC by TEM showed abnormalities in TB-stained cells including mitochondrial disruption, dilation of the endoplasmic reticulum cisterns, increased cytoplasmic and nuclear electron density and abnormalities in the nuclear profile. Statistical analysis using the Mann-Whitney test on morphometric data from micrographies showed significant morphologic differences between the two groups, both regarding longest nuclear axis difference and the ratio between the total nuclear perimeter and the cell area (p=0.03). No statistically significant difference was observed in capsule thickness, the LEC and the grouping of these two structures obtained from routine OM (p=0.1). Trypan blue is toxic to LECs, and cause abnormalities indicative of cell death. We observed molecular and morphologic aspects of cell death both by the mechanism of apoptosis and autophagy. Our findings lend support to the hypothesis that staining with 0.1% TB can help prevent or reduce the incidence of posterior capsule opacification following cataract surgery

Pseudoexfoliation (PEX) syndrome is an age-related condition characterized by the production and accumulation of extracellular fibrillary material in the anterior segment of the eye. PEX predisposes for several pathological conditions, such as glaucoma and complications during and after cataract surgery. The pathogenesis of PEX is not yet fully understood. It is multifactorial with genetics and ageing as contributing factors. We aimed to study the proteome in aqueous humor (AH) in PEX in order to increase the knowledge about its pathophysiology. Therefore, we developed sampling techniques and evaluated separation methods necessary for analyzing small sample volumes. Other objectives were to study the lens capsule in eyes with PEX regarding small molecules, and to investigate the association between PEX and cataract surgery in a population-based 30-year follow-up study. Samples of AH from eyes with PEX and control eyes were collected during cataract surgery. In pooled, and individual samples, various liquid based separation techniques and high resolution mass spectrometry were utilized. For quantitation, various methods for labeling, and label free techniques were applied. Lens capsules were collected from some of the patients, and analysed by imaging mass spectrometry. A cohort of 1,471 elderly individuals underwent a comprehensive ophthalmological examination at baseline. Medical information was obtained by questionnaires, and from medical records. Incident cases of cataract surgery were identified by review of medical records. In the initial study, several techniques were explored for protein detection, and a number of proteins were identified as differentially expressed. In the individually labelled samples, changes in the proteome were observed. Eyes with PEX contained higher levels of proteins involved in inflammation, oxidative stress, and coagulation, suggesting that these mechanisms are involved in the pathogenesis in PEX. The levels of β/γ-crystallins were significantly increased in PEX, which is a novel finding. In the lens capsules from individuals with PEX, changes in the lipid composition was observed with time-of-flight secondary ion mass spectrometry. These changes remain to be elucidated. By multivariate analysis, lens opacities were the first, and PEX the second most important predictor for cataract surgery, the later accounting for a 2.38-fold increased risk for cataract surgery.