Ocular parameters and anthropometry in Indo-Trinidadians.

To assess ocular parameters and their association with anthropometric measurements in Indo-Trinidadians adults. This was a clinical, descriptive, cross-sectional study of ocular parameters and anthropometry in adults Trinidadians of South Asian descent (Indo-Trinidadian). Ocular parameters were measured using optical coherence tomography, intraocular lens master biometer, and an autorefractor. Weight, height, and body mass index (BMI) were measured by anthropometry. Univariable and multivariable linear regressions were used to determine the association between demographic variables, anthropometric and ocular parameters. A total of 149 participants (298 eyes) comprising of 90 females (60.6%) and 59 males (39.4%). Aged 18 to 67 participated in the study. Males were taller, heavier, and had longer axial lengths than females which were statistically significant (P < .05). Age was negatively correlated with central corneal thickness (CCT) (r = -0.353, P = .044) and retinal nerve fiber layer thickness (r = -0.348, P = .047) but positively correlated with lens thickness (R = 0.881, P < .001). Education level was positively associated with CCT (R = 0.408, P = .018) but negatively associated with lens thickness (r = -0.521, P = .002). Weight was negatively correlated with corneal topography (r = -0.427, P = .013). Height was negatively correlated with cup-to-disc ratio (r = -0.410, P = .018), CCT (r = -0.382, P = .028), and corneal topography (r = -0.453, P = .008). There was no correlation between BMI, ocular parameters and CCT. There was a significant difference in the ocular parameters between males and females of South Asian descent in Trinidad and Tobago. Weight was negatively associated with the corneal topography. Height was negatively associated with the cup-to-disc ratio, central corneal thickness, and corneal topography. BMI had no statistically significant association with the ocular parameters investigated.

Specular microscopy of the corneal endothelial cells of bovines: an ex vivo study.

Background: The endothelium is the most posterior layer of the cornea and is essential for maintaining corneal transparency. Due to variations in corneal endothelial parameters among different species, knowledge of the normal parameters for each species is crucial. Aim: To evaluate the corneal endothelium of bovines using contact specular microscopy. Methods: Twenty eyeballs from 10 male Brangus (Bos taurus) aged 24 months were evaluated. Contact specular microscopy was performed on the central corneal area. The analyzed parameters were endothelial cell density (ECD) and endothelial cell morphology. Results: The ECD in the central area was 1,277 cells/mm2. Regarding the morphology, mainly cells with six (74.3%), five (14.7%) and seven sides (10%) were found. There were no significant differences in ECD and morphology between left and right eyes. Conclusion: Contact specular microscopy facilitated the analysis and measurement of corneal endothelial parameters in bovines. The data obtained will serve as a reference for the analysis of bovine corneal endothelium.

Actualización diagnóstica y terapéutica sobre la úlcera corneal / Diagnostic and therapeutic updating about the corneal ulcer

Se realizó una revisión bibliográfica exhaustiva sobre la anatomía de la córnea, a fin de profundizar en los principales factores predisponentes de la úlcera corneal, sus causas, cuadro clínico, evolución, complicaciones y tratamiento. Se analizó conceptualmente la enfermedad y se propuso incluir en su concepto el método clínico como premisa. Actualmente, en la provincia de Santiago de Cuba, la curación de estas úlceras constituye un problema de salud a resolver, puesto que los tratamientos convencionales no siempre permiten una evolución estable de los pacientes diagnosticados, razón por la cual surge la necesidad de buscar medicamentos y alternativas terapéuticas para tratar a dichos pacientes.

An exhaustive literature review on the cornea anatomy was carried out in order to deepen in the main predisposing factors of the corneal ulcer, their causes, clinical picture, clinical course, complications and treatment. The disease was conceptually analyzed and it was suggested to include in its concept the clinical method as premise. At the moment, in Santiago de Cuba province, the cure of these ulcers constitutes a health problem to solve, since the conventional treatments not always allow a stable clinical course of the diagnosed patients, reason why there is a necessity of searching medicines and therapeutic alternatives to treat them.

Corneal biomechanics and glaucoma beyond the bidirectional impact of intraocular pressure and corneal deformation response / Biomecânica corneana e glaucoma além do impacto bididirecional da pressão intraocular e da resposta da deformação corneana

ABSTRACT The purpose of this study was to highlight the impact of biomechanical corneal response in available in vivo tonometry methods for glaucoma management. Systematic review of non-contact air-puff tonometers that analyzes the corneal deformation response, with special focus on the investigation of the correlation of derived parameters with intraocular pressure measurements. The two actual and commercially available in vivo corneal tonometers provide promising information about biomechanical characteristics of the cornea and its relation to glaucoma, allowing the development of new protocols to evaluate, diagnose, and manage this disease.

RESUMO O objetivo deste estudo é destacar o impacto da resposta biomecânica corneana em métodos de tonometria in vivo disponíveis para o manejo do glaucoma. Trata-se de revisão sistemática de tonômetros de ar que analisa a resposta à deformação corneana, com foco especial na investigação da correlação dos parâmetros derivados com as medições da pressão intraocular. Os dois tonômetros mais recentes e comercialmente disponíveis fornecem informações promissoras sobre as características biomecânicas da córnea e sua relação com o glaucoma, permitindo o desenvolvimento de novos protocolos para avaliar, diagnosticar e controlar a doença.

Corneal and anterior chamber morphology in patients with noninfectious intraocular inflammation / Morfologia da córnea e da câmara anterior em pacientes com inflamação intraocular não infecciosa

ABSTRACT Purpose: To evaluate the corneal and anterior chamber morphology in phakic eyes with noninfectious intraocular inflammation. Methods: This study included 59 eyes with active uveitis, 62 with inactive uveitis, and 95 healthy eyes. Corneal endothelial cell density, hexagonal cell ratio, coefficient of variation (CV), corneal thickness and volume, maximum keratometry, and anterior chamber volume and depth (ACD) measurements were performed using a specular microscope and Pentacam HR. Results: The mean duration of uveitis was 24.6 ± 40.5 (0-180) months. The mean number of uveitis attacks was 2.8 ± 3.0 (1-20). Coefficient of variation was significantly higher in the active uveitis group compared with inactive uveitis group (p=0.017, Post Hoc Tukey). Anterior segment parameters other than coefficient of variation were not significantly different between active/inactive uveitis and control groups (p>0.05). Multiple linear regression analysis showed that coefficient of variation was greater in active uveitis compared with inactive uveitis after adjusting for the duration of uveitis, type of uveitis, having a rheumatologic disease, and having immunosuppressive treatment (p=0.003). The duration of uveitis and number of attacks were not significantly correlated with ocular parameters (p>0.05, Spearman's correlation). The difference in parameters was not significant based on uveitis type (p>0.05). Conclusions: Coefficient of variation was higher in eyes with active uveitis than that in eyes with inactive uveitis, whereas corneal endothelial cell density and anterior chamber morphology did not significantly differ between active/inactive uveitis and control groups.(AU)

RESUMO Objetivo: Avaliar a morfologia da córnea e da câmara anterior em olhos fácicos com inflamação intraocular não infecciosa. Métodos: Esse estudo incluiu 59 olhos com uveíte ativa, 62 olhos com uveíte inativa e 95 olhos saudáveis. A densidade de células endoteliais da córnea, a proporção de células hexagonais, o coeficiente de variação, o volume e a espessura da córnea, a ceratometria máxima e o volume e profundidade da câmara anterior foram medidos com um microscópio especular e uma Pentacam HR. Resultados: A duração média da uveíte foi de 24,6 ± 40,5 (0-180) meses. O número médio de crises de uveíte foi de 2,8 ± 3,0 (1-20). O coeficiente de variação foi significativamente maior no grupo com uveíte ativa do que no grupo com uveíte inativa (p=0,017, Tukey post-hoc). Não houve diferença significativa nos demais parâmetros do segmento anterior entre os grupos com uveíte ativa, com uveíte inativa e controle (p>0,05). A análise de regressão linear múltipla demonstrou que o coeficiente de variação foi maior na uveíte ativa do que na uveíte inativa, após ajustes para a duração e tipo de uveíte e a presença ou não de doença reumática e de tratamento imunossupressor (p=0,003). A duração da uveíte e o número de crises não demonstraram correlação significativa com os parâmetros oculares (p>0,05, correlação de Spearman). A diferença nos parâmetros não demonstrou correlação significativa com o tipo de uveíte (p>0,05). Conclusões: O coeficiente de variação foi maior nos olhos com uveíte ativa do que naqueles com uveíte inativa, ao passo que a densidade de células endoteliais e a morfologia da câmara anterior não mostraram diferenças significativas entre os grupos com uveíte ativa, com uveíte inativa e controle.(AU)

THE EYE OF CRAB-EATING FOX (CERDOCYON THOUS): ANATOMICAL CHARACTERISTICS AND NORMATIVE VALUES OF SELECTED DIAGNOSTIC TESTS, MORPHOMETRY OF CORNEAL TISSUE, AND ARRANGEMENTS OF CORNEAL STROMAL COLLAGEN FIBERS.

This study aimed to evaluate the ophthalmic parameters, morphometric features of corneal tissue, and arrangements of corneal stromal collagen fibers in crab-eating fox (Cerdocyon thous), a species of neotropical wild canid. We conducted the study on six juvenile crab-eating foxes (12 eyes), whilst 16 eyes were obtained post mortem from eight adult crab-eating foxes. The research was divided into two stages. In the first stage, eye anatomical characteristics, tear production (Schirmer 1 tear test, STT1), intraocular pressure (IOP), ocular echobiometry, and specular microscopy parameters related to morphology of corneal endothelium were studied in juvenile animals. In the second stage, morphometric features of corneal tissue (central corneal thickness [CCT] and corneal epithelium thickness) and arrangements of stromal collagen fibers were studied using eyes from adult animals. The main findings were that crab-eating fox eyes have vertical-slit pupils, holangiotic retina, and reference values (mean ± SD) of 13.37 ± 3.79 mm/min for STT1 and of 10.43 ± 3.84 mmHg for IOP. The ocular echobiometric features observed in crab-eating foxes are different from those reported for domestic dogs (Canis familiaris). Conversely, the corneal endothelial parameters are similar to those of domestic dogs. The CCT measured by tissue morphometry was 0.54 ± 0.06 mm, and the corneal epithelium thickness was 60.13 ± 8.71 µm. Mean coherency related to alignment of collagen fibers was 0.66 ± 0.12. The crab-eating fox cornea had predominantly thick collagen fibers. Crab-eating fox eyes have morphofunctional peculiarities. They resemble the eyes of domestic dogs in some aspects, but diverge in others.

Primary megalocornea: Case report. / Megalocórnea esencial: relato de caso.

The neonate has a horizontal diameter of the cornea, usually up to 10mm with growth up to 2mm in the first 2 years of life. We report a case of megalocornea, a rare, recessive, X-linked disorder in a 3-month-old child, seeking to review what the medical literature brings information about the condition, as well as diagnostic and follow-up parameters, of its main differential diagnoses.

T2 formula in a highly myopic population, comparison with other methods and description of an improved approach for estimating corneal height.

BACKGROUND: To determine the accuracy of the T2 formula as applied to highly myopic eyes, to compare the T2 formula to the SRK/T and Holladay 1 formulas, and to describe possible ways to improve the estimation of corneal height and prediction error in two settings, the Hadassah Hospital, Ophthalmology Department, Jerusalem, Israel and Clínica Barraquer, Bogotá, Colombia. METHODS: In this retrospective case series, optical biometer measurements were taken for 63 highly myopic patients (> 25 mm) undergoing uneventful crystalline lens phacoemulsification and insertion of an acrylic intraocular lens. Prediction errors were obtained, with estimations of ±0.50 D, ± 1.00 D, and greater than ±2.00 D. A method to improve the corneal height calculation is described. RESULTS: The SRK/T formula (mean absolute error [MAE] = 0.418; median absolute error [MedAE] = 0.352) was the most accurate, followed by the T2 (MAE = 0.435; MedAE = 0.381) and Holladay 1 (MAE = 0.455; MedAE = 0.389) formulas. Both the SRK/T and T2 formulas overestimated corneal height, but values were higher with the T2 formula. Corneal height was more precisely estimated using an alternative method that, when combined with axial length optimization, resulted in lower MAE (0.425) and MedAE (0.365) values than when applying the T2 formula alone. CONCLUSIONS: The T2 formula seems to be less accurate than the SRK/T formula in highly myopic eyes. An improved corneal height estimation method is described for the the T2 formula.

Ocular tissue distribution in the State of São Paulo: analysis on corneal discarding reasons. / Distribuição do tecido ocular no Estado de São Paulo: análise por razões de descarte de córneas.

OBJECTIVE: to identify the reasons for refusal of corneas. METHOD: this was a cross-sectional, retrospective, descriptive and correlational study composed of 5,560 optical corneas. The information was taken from the notification, organ procurement and distribution centers database as well as donor records. Descriptive statistics were used for the analysis of categorical variables and specific tests with a significance level of 5% for assessing the associations between variables. This study met the ethical aspects of scientific research. RESULTS: 60% of the donors were male and 40% died by circulatory problems. The main reason for refusal as informed by transplant teams is the donor's age and the endothelial cell count. For each year added to the donor's age, there is a 1% decrease in the chance that this cornea will be used for transplantation, and the increase of 100 cells per mm2 increases the chances that this cornea will be used by 9%. CONCLUSION: the main cause of refusal in the acceptance of corneal tissue is related to the age and the endothelial cell count.

Distribuição do tecido ocular no Estado de São Paulo: análise por razões de descarte de córneas / Ocular tissue distribution in the State of São Paulo: analysis on corneal discarding reasons / Distribución del tejido ocular en el estado de Sao Paulo: análisis sobre razones de descarte corneal

Objetivo identificar os motivos da recusa de córneas. Método estudo transversal, retrospectivo, descritivo e correlacional, composto por 5.560 córneas ópticas. As informações foram extraídas do banco de dados da Central de Notificação, Captação e Doação de Órgãos (CNCDO), bem como de prontuários de doadores. A estatística descritiva foi utilizada para a análise das variáveis categóricas e testes específicos, com nível de significância de 5% para avaliar as associações entre as variáveis. Este estudo atendeu aos aspectos éticos da pesquisa científica. Resultados 60% dos doadores eram do sexo masculino e 40% morreram por problemas circulatórios. Os principais motivos de recusa informados pelas equipes de transplante são a idade do doador e a contagem de células endoteliais. Para cada ano adicionado à idade do doador, há uma redução de 1% na chance de que essa córnea seja usada para transplante, e para cada acréscimo de 100 células por mm2 aumenta as chances de que essa córnea seja usada em 9%. Conclusão a principal causa de recusa na aceitação do tecido corneano está relacionada à idade e à contagem de células endoteliais.

Objective to identify the reasons for refusal of corneas. Method this was a cross-sectional, retrospective, descriptive and correlational study composed of 5,560 optical corneas. The information was taken from the notification, organ procurement and distribution centers database as well as donor records. Descriptive statistics were used for the analysis of categorical variables and specific tests with a significance level of 5% for assessing the associations between variables. This study met the ethical aspects of scientific research. Results 60% of the donors were male and 40% died by circulatory problems. The main reason for refusal as informed by transplant teams is the donor's age and the endothelial cell count. For each year added to the donor's age, there is a 1% decrease in the chance that this cornea will be used for transplantation, and the increase of 100 cells per mm2 increases the chances that this cornea will be used by 9%. Conclusion the main cause of refusal in the acceptance of corneal tissue is related to the age and the endothelial cell count.

Objetivo identificar los motivos para el rechazo de córneas. Método estudio transversal, retrospectivo, descriptivo y correlacional, compuesto por 5.560 córneas ópticas. La información se obtuvo de la bases de datos de Centros de Notificación, Obtención de Órganos y Distribución, así como de los registros de los donantes. Se utilizaron estadísticas descriptivas para analizar las variables categóricas y pruebas específicas con un nivel de significación de 5%, para evaluar las asociaciones entre variables. Este estudio contempla los aspectos éticos de una investigación científica. Resultados el 60% de los donantes eran hombres y el 40% falleció por problemas circulatorios. La principal razón del rechazo, informada por los equipos de trasplante, es la edad del donante y el recuento de las células endoteliales. Por cada año agregado a la edad del donante, existe una disminución de 1% en la probabilidad de que la córnea pueda ser utilizada para trasplante; el aumento de 100 células por mm2 aumenta la posibilidad de que esta córnea será usada por 9%. Conclusión la principal causa de rechazo en la aceptación del tejido corneal está relacionada con la edad y el recuento de células endoteliales.

Relationship between the biomechanical properties of the cornea and anterior segment measurements.

OBJECTIVE: To evaluate the relationship of biomechanical properties, corneal hysteresis and corneal resistance factor with age, sex and various corneal parameters measured with a Pentacam in normal subjects. METHODS: A total of 226 eyes from 113 patients were enrolled in this study. The subjects underwent Ocular Response Analyzer and Pentacam evaluations. A varying-intercept multilevel regression was implemented using Bayesian inference. The predictor variables were age, sex, central corneal thickness, corneal volume at a 7-mm diameter, anterior chamber angle and volume, anterior chamber depth, mean radius of the corneal curvature and corneal astigmatism. RESULTS: Corneal hysteresis ranged from 5.5 to 14.8 mmHg (mean 10.42±1.74 mmHg), and the corneal resistance factor ranged from 5.7 to 15.5 mmHg (mean 10.23±1.88 mmHg). No predictor variable other than gender and central corneal thickness had a significant correlation with either corneal hysteresis or corneal resistance factor. Corneal hysteresis was positively associated with female sex and with central corneal thickness, and corneal resistance factor was positively associated with central corneal thickness. CONCLUSION: Despite the associations found, only a small fraction of the variance in biomechanical measurements could be explained by the descriptors that were evaluated, indicating the influence of other corneal aspects on the biomechanical characteristics.

Assessment of non-invasive tear break-up time and tear meniscus height after instillation of three different formulations of anesthetic eye drops by Oculus Keratograph 5M / Avaliação do tempo de ruptura lacrimal não invasivo e da altura do menisco lacrimal após a instilação de três diferentes formulações de colírio anestésico por Oculus Keratograph 5M

Abstract Purpose: To assess the non-invasive tear break-up time (NITBUT) and tear meniscus height (TMH) after instilling the three different types of anesthetic eye drops by Oculus Keratograph 5M. Methods: In this prospective study, 85 healthy subjects (85 eyes) were randomly divided into three groups. The groups were randomly received lidocaine hydrochloride 2%, proparacaine hydrochloride 0.5%, and tetracaine hydrochloride 0.5%. The qualitative and quantitative parameters of tear film were assessed using NITBUT and TMH, respectively. In all groups, the quantity of tear film using TMH was measured in the right eye of subjects, while the quality of tear film using NITBUT was assessed in the left eye. The analysis of variance (ANOVA) was used to compare the difference between before and after the intervention. A P-value < 0.05 was considered significant. Results: Differences for TMH and NITBUT between before and after applying lidocaine hydrochloride 2% were not statistically significant (P > 0.05). The mean values of NITBUT and TMH after the instillation of proparacaine hydrochloride 0.5% showed a significant decrease than before the intervention (P < 0.05). Also, after the use of tetracaine hydrochloride 0.5%, the mean value of NITBUT was significantly increased (P < 0.05), but the mean value of TMH was significantly decreased than before the intervention (P < 0.05). Conclusion: Our study showed that lidocaine hydrochloride 2% as an anesthetic eye drops can be an appropriate choice for eye examinations due to a lack of significant effect on the quantity and quality of tear film.

Resumo Objetivo: Avaliar o tempo de ruptura lacrimal não invasivo (NITBUT) e a altura do menisco lacrimal (TMH) após instilar os três tipos diferentes de colírio anestésico pelo Oculus Keratograph 5M. Métodos: Neste estudo prospectivo, 85 indivíduos saudáveis (85 olhos) foram divididos aleatoriamente em três grupos. Os grupos receberam aleatoriamente cloridrato de lidocaína a 2%, cloridrato de proparacaína a 0.5% e cloridrato de tetracaína a 0.5%. Os parâmetros qualitativos e quantitativos do filme lacrimal foram avaliados utilizando NITBUT e TMH, respectivamente. Em todos os grupos, a quantidade de filme lacrimal utilizando TMH foi medida no olho direito dos sujeitos, enquanto a qualidade do filme lacrimal usando NITBUT foi avaliada no olho esquerdo. A análise de variância (ANOVA) foi utilizada para comparar a diferença entre antes e depois da intervenção. Um valor de P < 0.05 foi considerado significativo. Resultados: Diferenças para TMH e NITBUT entre antes e depois da aplicação de cloridrato de lidocaína a 2% não foram estatisticamente significantes (P > 0.05). Os valores médios de NITBUT e TMH após a instilação de cloridrato de proparacaína a 0.5% mostraram uma diminuição significativa do que antes da intervenção (P < 0.05). Além disso, após o uso de cloridrato de tetracaína a 0.5%, o valor médio de NITBUT foi significativamente aumentado (P < 0.05), mas o valor médio de TMH foi significativamente menor do que antes da intervenção (P < 0.05). Conclusão: Nosso estudo mostrou que o cloridrato de lidocaína a 2% como colírio anestésico pode ser uma escolha apropriada para exames oftalmológicos devido à falta de efeito significativo sobre a quantidade e a qualidade do filme lacrimal.

Thickness and immunohistochemistry of LASIK flaps created by different femtosecond lasers in eye-bank corneas / Espessura e imunohistoquímica de flap de LASIK criado com diferentes laseres de femtosegundo em córneas de banco de olhos

ABSTRACT Purpose: The aim of this study was to compare the corneal cell viability and thickness of LASIK flaps created by 3 femtosecond lasers in eye-bank human corneas. Methods: Forty-five eye-bank human sclerocorneal buttons (15 corneas in each group) were examined after the creation of 120 mm-thick laser-assisted keratomileusis (LASIK) flaps with 150kHz iFS In­traLase™ (IL), Z6 Femto LDV™ (LDV), or 200kHz Wavelight™ FS200 (FS200). The thickness of the flaps was measured using anterior segment optical coherence tomography (AS-OCT; Visante™). Cell viability was blindly evaluated with immunohistochemistry for keratocyte apoptosis using anti-caspase 3 antibodies. Results: The standard deviation from the intended flap thickness was less than 10 mm in all the groups. There was a statistically significant difference in corneas treated with LDV and IL with regard to the flap thickness horizontally at +3.00 mm (p=0.0124), -0.5 mm (p=0.0082), and -1.00 mm (p=0.0425) from the corneal vertex and +0.5 mm from the flap edge (p=0.0240), and those treated with LDV and FS200 with regard to the flap thickness horizontally at -0.5 mm from the corneal vertex (p=0.0082). The mean keratocyte apoptosis numbers were 13.09 ± 1.10, 15.59 ± 3.28, and 17.72 ± 1.49 in corneas treated with IL, FS200, and LDV, respectively (p<0.001). Conclusion: All 3 assessed femtosecond lasers provided predictable LASIK flap thickness. The mean stromal keratocyte apoptosis number was low in all groups.

RESUMO Objetivos: Comparar a viabilidade celular e a espessura do disco de LASIK confeccionado por três laseres de femtosegundo, em córneas humanas de banco de olhos. Métodos: Quarenta e cinco botões córneo-esclerais humanos de banco de olhos (15 córneas em cada grupo) foram examinados, após a criação de disco de LASIK com 120 mm de espessura, utilizando-se o iFS IntraLase® 150kHz (IL), o Femto LDV® Z6 (LDV), ou o Wavelight® FS200 200kHz (FS200). Tomografia de coerência óptica do seguimento anterior (OCT Visante®) foi usada para medir a espessura dos discos. A viabilidade celular foi avaliada por meio de imuno-histoquímica para apoptose dos ceratócitos, com anti-caspase 3. Resultados: O desvio padrão da espessura planejada do disco foi inferior a 10 mm em todos os grupos. Houve diferença estatisticamente significante da espessura do disco horizontalmente a +3,00 mm (p=0,0124), -0,5 mm (p=0,0082) e -1,00 mm (p=0,0425), a partir do vértice corneal, e a +0,5 mm (p=0,0240), a partir da borda do disco, em córneas tratadas por LDV e IL, e horizontalmente a -0,5 mm a partir do vértice corneal, entre LDV e FS200 (p=0,0082). A média de apoptose dos ceratócitos foi (13,09 ± 1,10), (15,59 ± 3,28) e (17,72 ± 1,49), em córneas tratadas pelo IL, FS200 e LDV, respectivamente (p<0,001). Conclusão: Todos os três laseres de femtosegundo estudados produziram disco de LASIK com predictibilidade de espessura. A média de apoptose dos ceratócitos foi baixa em todos os grupos.

Thickness and immunohistochemistry of LASIK flaps created by different femtosecond lasers in eye-bank corneas.

PURPOSE: The aim of this study was to compare the corneal cell viability and thickness of LASIK flaps created by 3 femtosecond lasers in eye-bank human corneas. METHODS: Forty-five eye-bank human sclerocorneal buttons (15 corneas in each group) were examined after the creation of 120 mm-thick laser-assisted keratomileusis (LASIK) flaps with 150kHz iFS In-traLase™ (IL), Z6 Femto LDV™ (LDV), or 200kHz Wavelight™ FS200 (FS200). The thickness of the flaps was measured using anterior segment optical coherence tomography (AS-OCT; Visante™). Cell viability was blindly evaluated with immunohistochemistry for keratocyte apoptosis using anti-caspase 3 antibodies. RESULTS: The standard deviation from the intended flap thickness was less than 10 mm in all the groups. There was a statistically significant difference in corneas treated with LDV and IL with regard to the flap thickness horizontally at +3.00 mm (p=0.0124), -0.5 mm (p=0.0082), and -1.00 mm (p=0.0425) from the corneal vertex and +0.5 mm from the flap edge (p=0.0240), and those treated with LDV and FS200 with regard to the flap thickness horizontally at -0.5 mm from the corneal vertex (p=0.0082). The mean keratocyte apoptosis numbers were 13.09 ± 1.10, 15.59 ± 3.28, and 17.72 ± 1.49 in corneas treated with IL, FS200, and LDV, respectively (p<0.001). CONCLUSION: All 3 assessed femtosecond lasers provided predictable LASIK flap thickness. The mean stromal keratocyte apoptosis number was low in all groups.

Positions of Ocular Geometrical and Visual Axes in Brazilian, Chinese and Italian Populations.

PURPOSE: To identify the relative positions of geometrical and visual axes of the eye and present a method to locate the visual center when the geometrical axis is taken as a reference. METHODS: Topography elevation data was collected using a Pentacam HR ® topographer from 2040 normal eyes of 1020 healthy participants in Brazil, China and Italy. A three-dimensional, rotation algorithm, a first-order Zernike polynomial fit and a nonlinear least-squares error function was used within an optimization function to locate the geometrical axis and the visual center of each eye. RESULTS: The right eyes of participants were significantly more tilted than left eyes throughout the topography scanning process (p < 0.001). The visual centers were always located in the nasal-superior quadrant, although the visual centers of fellow eyes were not symmetrically located. Mean distances between the visual center and the geometrical center in right eyes were 0.8 ± 0.29 mm, 0.56 ± 0.18 mm and 0.91 ± 0.34 mm among Brazilian, Chinese and Italian participants, respectively, and located at angular positions of 38.7 ± 24.5°, 23.0 ± 29.8° and 23.1 ± 28.1° from the nasal side. However, in left eyes, mean distances were 0.76 ± 0.33 mm, 0.45 ± 0.12 mm and 0.75 ± 0.33 mm at polar angles from the nasal side of 59.3 ± 29.0°, 50.6 ± 44.5° and 61.8 ± 34.1°, respectively. CONCLUSIONS: Fellow eyes do not perform similarly during the fixation process, with right eyes tending to tilt more than left eyes, and the visual centers of the fellow eyes positioned differently relative to the geometrical centers.

Reproducibility of the measurement of central corneal thickness in healthy subjects obtained with the optical low coherence reflectometry pachymeter and comparison with the ultrasonic pachymetry. / Evaluación de la reproducibilidad en la medición del grosor corneal central con el paquímetro de reflectometría óptica de baja coherencia y comparación con el paquímetro ultrasónico en sujetos sanos

Background: Corneal pachymetry is widely used for refractive surgery and follow up in keratoconus, accurate measurement is essential for a safe surgery. Objective: To assess intraobserver reliability of central corneal thickness (CCT) measurements using optical low-coherence reflectometry (OLCR) technology and its agreement with ultrasonic pachymeter (US). Method: Randomized and prospective comparative evaluation of diagnostic technology. One randomly healthy eye of subjects was scanned three times with both devices. Intraobserver within-subject standard deviation (Sw), coefficient of variation (CVw) and intraclass correlation coefficient (ICC) were obtained for reliability analysis; for study agreement, data were analyzed using the paired-sample t test and the Bland-Altman LoA method. The mean of three scans of each equipment was used to assess the LoA. Results: The study enrolled 30 eyes of 30 subjects with average age of 28.70 ± 8.06 years. For repeatability, the Sw were 3.41 and 5.96 µ, the intraobserver CVw was 2 and 4% and ICC 0.991 and 0.988, for OLCR and US respectively. The mean CCT difference between OLCR and US was 8.90 ± 9.03 µ (95% confidence interval: 5.52-2.27 µ), and the LoA was 35.40 µ. Conclusions: OLCR technology provided reliable intraobserver CCT measurements. Both pachymetry measurements may be used interchangeably with minimum calibration adjustment.

Antecedentes: La paquimetría corneal es ampliamente utilizada para la cirugía refractiva y el seguimiento de pacientes con queratocono. La medición exacta es esencial para una cirugía refractiva segura. Objetivo: Evaluar la reproducibilidad intraobservador en la medición del grosor corneal central (GCC) utilizando reflectometría óptica de baja coherencia (OLCR) y su concordancia con la paquimetría ultrasónica. Método: Estudio prospectivo, comparativo y aleatorizado de una tecnología diagnóstica. Se midió de forma aleatorizada un ojo de cada sujeto en tres ocasiones con ambos equipos. Para el análisis de fiabilidad se obtuvieron la desviación estándar (DE) intrasujeto, el coeficiente de variación (CV) y el coeficiente de correlación intraclase (CCI). Para el estudio de concordancia se analizaron los datos usando una prueba t pareada simple, además de los límites de acuerdo de Bland-Altman (LA). Para la evaluación de los LA se utilizó el promedio de las tres mediciones de cada equipo. Resultados: El estudio incluyó 30 ojos de 30 sujetos con una edad promedio de 28.70 ± 8.06 años. Para la repetibilidad, la DE intrasujeto fue de 3.41 y 5.96 µ, el CV del 2 y el 4%, y el CCI de 0.991 y 0.988, para el OLCR y el paquímetro ultrasónico, respectivamente. La diferencia del GCC promedio entre el OLCR y el paquímetro ultrasónico fue de 8.90 ± 9.03 µ (intervalo de confianza del 95%: 5.52-2.27 µ), y el LA fue de 35.40 µ. Conclusiones: La tecnología de OLCR proporciona medidas del GCC intraobservador fiables. Ambas mediciones paquimétricas pueden usarse de forma intercambiable con mínimos ajustes de calibración.

Morphology of endothelial cells from different regions of the cornea of dogs / Morfologia das células endoteliais de diferentes regiões da córnea de cães

The aim of this study was to evaluate the morphology of endothelial cells from different areas of the cornea of dogs. Twenty healthy eyes from 10 dogs, females or males, of different ages were studied. Corneal endothelium morphology of superior, inferior, central, nasal and temporal areas was assessed by 0.2% alizarin red staining using an optic microscope. One hundred endothelial cells from each corneal area were analyzed. In all areas of the cornea studied were found endothelial cells with four sides, five sides, six sides and seven sides. There was no significant difference regarding endothelial cell morphology in all corneal regions evaluated. Thus, the morphology of the central cornea area represents the entire endothelial mosaic and may be applied to peripheral areas. Therefore, analysis of the central area is sufficient to estimate the shape of endothelial cells of peripheral areas of healthy dog corneas.(AU)

Objetivou-se avaliar a morfologia das células endoteliais de diferentes regiões da córnea de cães. Vinte olhos saudáveis de 10 cães, fêmeas ou machos, de diferentes idades foram estudados. A morfologia do endotélio corneano das regiões superior, inferior, central, nasal e temporal foi avaliada pela coloração vermelho de alizarina 0,2% com microscópio óptico. Foram analisadas 100 células endoteliais de cada região da córnea. Em todas as regiões da córnea estudadas foram encontradas células endoteliais com quatro lados, cinco lados, seis lados e sete lados. Não houve diferença significativa em relação à morfologia de células endoteliais da córnea em todos as regiões estudadas. Assim, a morfologia da região central da córnea representa todo o mosaico endotelial e pode ser aplicada em áreas periféricas. Portanto, a análise da área central é suficiente para estimar a forma das células endoteliais das áreas periféricas de córneas de cães saudáveis.(AU)

Relationship between the biomechanical properties of the cornea and anterior segment measurements

OBJECTIVE: To evaluate the relationship of biomechanical properties, corneal hysteresis and corneal resistance factor with age, sex and various corneal parameters measured with a Pentacam in normal subjects. METHODS: A total of 226 eyes from 113 patients were enrolled in this study. The subjects underwent Ocular Response Analyzer and Pentacam evaluations. A varying-intercept multilevel regression was implemented using Bayesian inference. The predictor variables were age, sex, central corneal thickness, corneal volume at a 7-mm diameter, anterior chamber angle and volume, anterior chamber depth, mean radius of the corneal curvature and corneal astigmatism. RESULTS: Corneal hysteresis ranged from 5.5 to 14.8 mmHg (mean 10.42±1.74 mmHg), and the corneal resistance factor ranged from 5.7 to 15.5 mmHg (mean 10.23±1.88 mmHg). No predictor variable other than gender and central corneal thickness had a significant correlation with either corneal hysteresis or corneal resistance factor. Corneal hysteresis was positively associated with female sex and with central corneal thickness, and corneal resistance factor was positively associated with central corneal thickness. CONCLUSION: Despite the associations found, only a small fraction of the variance in biomechanical measurements could be explained by the descriptors that were evaluated, indicating the influence of other corneal aspects on the biomechanical characteristics.

Utilização de modelos geométricos simplificados de uma córnea para fins de otimização / Use of simplified geometrical models of a cornea for optimization purposes

Resumo Otimização por Enxame de Partículas (PSO) é uma técnica de inteligência artificial (AI), que pode ser usada para encontrar soluções aproximadas para problemas numéricos de maximização e minimização extremamente difíceis. Neste trabalho, utilizou-se um algoritmo PSO para comparar os deslocamentos sofridos por uma amostra de córnea humana submetida à uma pressão interna de 45 mmHg com resultados de simulações numéricas e identificar valores otimizados para propriedades hiperelásticas da córnea (µ e α). Por meio dos resultados das simulações via análise inversa pelo Método dos Elementos Finitos (MEF), em conjunto com o algoritmo PSO, foram encontrados valores otimizados de µ = 0,047 e α = 106,7. Quando comparado com resultados otimizados por meio de um software comercial, foram encontrados erros de aproximadamente 0,15%. Por meio dos resultados obtidos, verificou-se ainda que, variando os valores dos coeficientes de inércia da partícula no algoritmo PSO, os resultados podem sofrer ligeira melhoria, o que demonstra potencial uso do PSO em conjunto com análise inversa do MEF para caracterização de materiais hiperelásticos, utilizando modelos geométricos simplificados

Abstract Particle Swarm Optimization (PSO) is an artificial intelligence technique (AI) that can be used to find approximate solutions to numerical problems of maximization and minimization. In this study, it was used a PSO algorithm to compare displacements from human cornea sample subjected to internal pressure of 45 mmHg with Results of numerical simulations were provided which identified optimized values for hyperelastic properties of the cornea (µ and α). By means of the results from numerical simulations via inverse analysis by the Finite Element Method (FEM), in conjunction with the PSO algorithm, optimized values of µ = 0.047 and α = 106.7 were found. When compared with optimized results from commercial software, errors around 0.15% were found. Results showed that, varying the values of particle inertia coefficients in the PSO algorithm, simulated displacements have improved when compared to experimental data. This demonstrates the potential use of PSO algorithm in conjunction with the FEM inverse analysis for hyperelastic materials characterization, using simplified geometrical models

Are the effects of hemodialysis on ocular parameters similar during and after a hemodialysis session?

PURPOSE: To evaluate the changes in several ocular parameters, including choroidal thickness, during and after hemodialysis. METHODS: Twenty-seven eyes of 27 patients with chronic renal failure undergoing hemodialysis were included. The patients underwent an ophthalmic examination, including intraocular pressure, central corneal thickness, iridocorneal angle, subfoveal choroidal thickness, and blood pressure, just before a hemodialysis session, during the second hour of the session, and half an hour after the end of the session. Body weight was measured before and after the session, and ultrafiltration volume was noted after the session. Central corneal thickness, intraocular pressure, and subfoveal choroidal thickness were measured by optical coherence tomography. RESULTS: In comparison with baseline levels, mean intraocular pressure and central corneal thickness increased significantly during the second hour of hemodialysis (p=0.001 and p=0.011, respectively) and showed no significant changes after hemodialysis (p=0.844 and p=0.246, respectively). Mean iridocorneal angle did not significantly change during the second hour of hemodialysis (p=0.101) and after hemodialysis (p=0.589). Mean subfoveal choroidal thickness was significantly lower during the second hour of hemodialysis (p<0.001) and after hemodialysis (p<0.001). CONCLUSIONS: Mean intraocular pressure and central corneal thickness increased and subfoveal choroidal thickness decreased during the second half of the hemodialysis session. During the second half of the session, intraocular pressure and central corneal thickness had a trend toward reduction, while subfoveal choroidal thickness had a relatively steady course. Because of possible fluctuations in the values, it would be reasonable to evaluate the changes not only from before to after hemodialysis but also during hemodialysis when analyzing the ocular effects of dialysis.