Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 69
Filtrar
Más filtros










Base de datos
Intervalo de año de publicación
1.
Artículo en Inglés | MEDLINE | ID: mdl-31395531

RESUMEN

OBJECTIVE: The human visual system alters its focus by a shape change of the eye lens. The extent to which the lens can adjust ocular refractive power is dependent to a significant extent on its material properties. Yet, the link between the optics and mechanics of the lens remains uncertain and relatively unexplored. This study aims to investigate this opto-mechanical link within the eye lens to gain insight into the processes of shape alteration and their respective decline with age. METHODS: Finite Element models based on biological lenses were developed for five ages: 16, 35, 40, 57 and 62 years by correlating in vivo measurements of the longitudinal modulus using Brillouin scattering with in vitro X-ray interferometric measurements of refractive index and taking into account various directions of zonular force. RESULTS: A model with radial cortical Young's moduli provides the same amount of refractive power with lesser change in thickness than a model with uniform cortical Young's modulus and shows uniform stress distributions with no discontinuities along the cortico-nucleus boundary. The direction of zonular angles can significantly influence curvature change regardless of the modulus distribution. CONCLUSIONS: The present paper proposes a modelling approach, coupling optical and mechanical properties of human eye lens, which reveals the effect of parameter choice on model response. SIGNIFICANCE: This advanced modelling approach, considering the important interplay between optical and mechanical properties, has potential for use in design of accommodating implant lenses and for investigating non-biological causes of pathological processes in the lens (e.g. cataract).

2.
J Opt Soc Am A Opt Image Sci Vis ; 36(4): B71-B76, 2019 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-31044958

RESUMEN

The purpose of this study was to evaluate the clinical utility of the output parameters of the ocular response analyzer (ORA) and those calculated from the raw ORA in subjects with healthy eyes and those with suspected glaucoma, and in patients with two types of glaucoma. The raw ORA data were analyzed using a custom software that included the Gaussian filtering of applanation curves for three different window sizes. To the best of our knowledge, these findings present a novel means of optimizing the use of measurements from the ORA, which can refine the characteristics of corneal biomechanics, enabling a distinction between the types of glaucoma and leading to an improvement in diagnosing and early detection.


Asunto(s)
Glaucoma/diagnóstico , Adulto , Anciano , Anciano de 80 o más Años , Fenómenos Biomecánicos , Diagnóstico Diferencial , Diagnóstico Precoz , Femenino , Humanos , Masculino , Persona de Mediana Edad , Programas Informáticos
3.
J Opt Soc Am A Opt Image Sci Vis ; 36(4): B116-B122, 2019 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-31044989

RESUMEN

Ageing changes to the various components of the accommodative system of the eye lens contribute to the loss of focusing power. The relative contributions of each ageing component, however, are not well defined. This study investigates the contribution of geometric parameters and material properties on accommodation, simulated using models based on human lenses aged 16, 35, and 48 years. Each model was tested using two different sets of material properties and a range of zonular fiber angles and was compared to results from in vivo measurements. The geometries and material parameters of older and younger lens models were interchanged to investigate the role of shape and material on accommodative capacity. Results indicate that geometry has the greater role in accommodation.


Asunto(s)
Acomodación Ocular , Envejecimiento/fisiología , Análisis de Elementos Finitos , Cristalino/fisiología , Fenómenos Mecánicos , Adolescente , Fenómenos Biomecánicos , Humanos , Persona de Mediana Edad
4.
Prog Retin Eye Res ; 2018 Nov 12.
Artículo en Inglés | MEDLINE | ID: mdl-30439450

RESUMEN

The ability of the human lens to accommodate is mediated by the ciliary muscle and zonule; the manifest optical power changes depend on the shape and material properties of the lens. The latter are difficult to measure with accuracy and, given the dynamic aspects of accommodation and the ageing of cells and tissues, the biomechanics of the lens is neither fixed nor constant. A range of techniques have been developed to measure both ageing trends and spatial variations in the mechanical properties and these have yielded a diverse array of findings and respective conclusions. The majority of quasi-static measurements, where the observation time is in minutes or hours, indicate that the stiffness of the lens increases with age at a faster rate in the lens centre than in the periphery. Dynamic measurements show that lens material properties are dependent on the loading frequency. Recent in vivo analyses suggest that, along the optic axis, profiles of elastic moduli are very similar to profiles of refractive index. This review assesses the advantages and limitations of different measurement techniques and consequent variations in elastic moduli that have been found. Consideration is given to the role of computational modelling and the various modelling methods that have been applied. The changes in mechanical properties of the lens associated with ageing and pathology and future implications for implant design are discussed.

5.
JMIR Med Inform ; 6(4): e47, 2018 Nov 22.
Artículo en Inglés | MEDLINE | ID: mdl-30467101

RESUMEN

BACKGROUND: The current law on anonymization sets the same standard across all situations, which poses a problem for biomedical research. OBJECTIVE: We propose a matrix for setting different standards, which is responsive to context and public expectations. METHODS: The law and ethics applicable to anonymization were reviewed in a scoping study. Social science on public attitudes and research on technical methods of anonymization were applied to formulate a matrix. RESULTS: The matrix adjusts anonymization standards according to the sensitivity of the data and the safety of the place, people, and projects involved. CONCLUSIONS: The matrix offers a tool with context-specific standards for anonymization in data research.

6.
Proteins ; 2018 Jul 18.
Artículo en Inglés | MEDLINE | ID: mdl-30019777

RESUMEN

Most molecular processes in living organisms rely on protein-protein interactions, many of which are mediated by ß-sheet interfaces; this study investigates the formation of ß-sheet interfaces through the conversion of coils into ß-strands. Following an exhaustive search in the Protein Data Bank, the corresponding structural dimorphic fragments were extracted, characterized, and analyzed. Their short strand lengths and specific amino acid profiles indicate that dimorphic ß-strand interfaces are likely to be less stable than standard ones and could even convert to coil interfaces if their environment changes. Moreover, the construction of a simple classifier able to discriminate between the sequences of dimorphic and standard ß-strand interfaces suggests that the nature of those dimorphic sequences could be predicted, providing a novel means of identifying proteins capable of forming dimers.

7.
Oxid Med Cell Longev ; 2018: 5260976, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29636847

RESUMEN

With advances in refractive surgery and demand for cataract removal and lens replacement, the ocular use of nonsteroidal anti-inflammatory drugs (NSAIDs) has increased. One of the most commonly used NSAIDs is diclofenac (Diclo). In this study, cyclodextrins (CDs), α-, ß-, γ-, and HP-ß-CDs, were investigated with in vitro irritation and in vivo ulceration models in rabbits to reduce Diclo toxicity. Diclo-, α-, ß-, γ-, and HP-ß-CD inclusion complexes were prepared and characterized and Diclo-CD complexes were evaluated for corneal permeation, red blood cell (RBCs) haemolysis, corneal opacity/permeability, and toxicity. Guest- (Diclo-) host (CD) solid inclusion complexes were formed only with ß-, γ-, and HP-ß-CDs. Amphipathic properties for Diclo were recorded and this surfactant-like functionality might contribute to the unwanted effects of Diclo on the surface of the eye. Contact angle and spreading coefficients were used to assess Diclo-CDs in solution. Reduction of ocular toxicity 3-fold to16-fold and comparable corneal permeability to free Diclo were recorded only with Diclo-γ-CD and Diclo-HP-ß-CD complexes. These two complexes showed faster healing rates without scar formation compared with exposure to the Diclo solution and to untreated groups. This study also highlighted that Diclo-γ-CD and Diclo-HP-ß-CD demonstrated fast healing without scar formation.


Asunto(s)
Córnea/fisiopatología , Ciclodextrinas/farmacología , Diclofenaco/efectos adversos , Animales , Rastreo Diferencial de Calorimetría , Bovinos , Muerte Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Córnea/efectos de los fármacos , Córnea/patología , Opacidad de la Córnea/tratamiento farmacológico , Opacidad de la Córnea/patología , Opacidad de la Córnea/fisiopatología , Ciclodextrinas/química , Ciclodextrinas/uso terapéutico , Diclofenaco/química , Eritrocitos/efectos de los fármacos , Eritrocitos/metabolismo , Hemólisis/efectos de los fármacos , Humanos , Simulación del Acoplamiento Molecular , Permeabilidad , Conejos , Espectroscopía Infrarroja por Transformada de Fourier , Tensión Superficial , Úlcera/tratamiento farmacológico , Úlcera/patología , Úlcera/fisiopatología
8.
JAMA ; 319(9): 935, 2018 03 06.
Artículo en Inglés | MEDLINE | ID: mdl-29509858
9.
Clin Ophthalmol ; 12: 201-205, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-29403261

RESUMEN

Purpose: To measure the maximum, objectively measured, accommodative amplitude, produced by pharmacologic stimulation. Methods: Thirty-seven healthy subjects were enrolled, with a mean age of 20.2±1.1 years, corrected visual acuity of 20/20, and mean spherical equivalent refraction (SER) =-0.83±1.60 diopters. For each subject, the right pupil was dilated with phenylephrine 10%. After 30 minutes, the pupil was measured, the left eye was patched, and the right eye was autorefracted. Pilocarpine 4% was then instilled in the right eye, followed by phenylephrine. At 45 minutes after the pilocarpine, autorefraction and pupil size were again measured. Results: Mean pupil size pre- and postpilocarpine was 8.0±0.8 mm and 4.4±1.9 mm, respectively. Pre- and postpilocarpine, the mean SER was -0.83±1.60 and -10.55±4.26 diopters, respectively. The mean pilocarpine-induced accommodative amplitude was 9.73±3.64 diopters. Five subjects had accommodative amplitudes ≥14.00 diopters. Accommodative amplitude was not significantly related to baseline SER (p-value =0.24), pre- or postpilocarpine pupil size (p-values =0.13 and 0.74), or change in pupil size (p-value =0.37). Iris color did not statistically significantly affect accommodative amplitude (p-value =0.83). Conclusion: Following topically applied pilocarpine, the induced objectively measured accommodation in the young eye is greater than or equal to the reported subjectively measured voluntary maximum accommodative amplitude.

10.
Graefes Arch Clin Exp Ophthalmol ; 256(2): 395-402, 2018 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-29147767

RESUMEN

PURPOSE: Our purpose was to determine the changes in anterior chamber depth (ACD) and central lens thickness (CLT) during pharmacologically induced accommodation. METHODS: Following pupillary dilation with phenylephrine 10%, baseline auto-refractions and swept-source optical coherence tomographic biometric images (Zeiss IOLMaster 700) were obtained from the right eyes of 25 subjects aged 19 to 24 years. Pilocarpine 4% and phenylephrine 10% were then instilled into these right eyes. One hour later, auto-refractions and biometric imaging were repeated. Only data from eight of 25 subjects met the following stringent criteria to be included in the study analysis: pre and post-pilocarpine biometric foveal images were registerable, the images of the corneal centers were shifted by ≤100 µm, pupils >5 mm and the pharmacologically induced refractive change was ≥ -7 diopters. RESULTS: The mean auto-refractive accommodative change for the eight included subjects was -12.45 diopters (± 3.45 diopters). The mean change in CLT was 81 µm (± 54 µm) and the mean change in ACD was -145 µm (± 86 µm). Superimposition of the registered pre and post-pilocarpine biometric images of the sagittal sections of the whole eye from each subject demonstrated that the position of the whole lens did not shift either anteriorly, posteriorly or vertically during pharmacologically induced accommodation. CONCLUSIONS: A small increase in lens thickness was associated with a large change in accommodative amplitude and no significant change in lens position as predicted by the Schachar theory.


Asunto(s)
Acomodación Ocular/fisiología , Cámara Anterior/diagnóstico por imagen , Segmento Anterior del Ojo/diagnóstico por imagen , Cristalino/fisiología , Refracción Ocular/fisiología , Adulto , Biometría/métodos , Femenino , Humanos , Cristalino/citología , Masculino , Pupila , Tomografía de Coherencia Óptica/métodos , Adulto Joven
11.
Biomed Opt Express ; 8(11): 4827-4837, 2017 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-29188084

RESUMEN

The gradient index (GRIN) model is the most accurate way to represent the eye lens which, because of its growth mode, is a lamellar, shell-like structure. The GRIN is thought to provide optical properties that counteract age-related changes in curvature that would otherwise create an increasingly myopic eye: the so-called lens paradox. This article investigates how fine-tuning the refractive index and the internal curvatures of the lenticular indicial contours may prevent the ageing eye from becoming myopic. A system matrix approach is applied for analysis of a shell model with 200 shells to obtain the paraxial characteristics of the eye model.

12.
Sci Rep ; 7(1): 16688, 2017 Nov 30.
Artículo en Inglés | MEDLINE | ID: mdl-29192148

RESUMEN

The lens provides refractive power to the eye and is capable of altering ocular focus in response to visual demand. This capacity diminishes with age. Current biomedical technologies, which seek to design an implant lens capable of replicating the function of the biological lens, are unable as yet to provide such an implant with the requisite optical quality or ability to change the focussing power of the eye. This is because the mechanism of altering focus, termed accommodation, is not fully understood and seemingly conflicting theories require experimental support which is difficult to obtain from the living eye. This investigation presents finite element models of the eye lens based on data from human lenses aged 16 and 35 years that consider the influence of various modelling parameters, including material properties, a wide range of angles of force application and capsular thickness. Results from axisymmetric models show that the anterior and posterior zonules may have a greater impact on shape change than the equatorial zonule and that choice of capsular thickness values can influence the results from modelled simulations.

13.
BMC Med Ethics ; 18(1): 27, 2017 04 08.
Artículo en Inglés | MEDLINE | ID: mdl-28388916

RESUMEN

The EU offers a suitable milieu for the comparison and harmonisation of healthcare across different languages, cultures, and jurisdictions (albeit with a supranational legal framework), which could provide improvements in healthcare standards across the bloc. There are specific ethico-legal issues with the use of data in healthcare research that mandate a different approach from other forms of research. The use of healthcare data over a long period of time is similar to the use of tissue in biobanks. There is a low risk to subjects but it is impossible to gain specific informed consent given the future possibilities for research. Large amounts of data on a subject present a finite risk of re-identification. Consequently, there is a balancing act between this risk and retaining sufficient utility of the data. Anonymising methods need to take into account the circumstances of data sharing to enable an appropriate balance in all cases. There are ethical and policy advantages to exceeding the legal requirements and thereby securing the social licence for research. This process would require the examination and comparison of data protection laws across the trading bloc to produce an ethico-legal framework compatible with the requirements of all member states. Seven EU jurisdictions are given consideration in this critique.


Asunto(s)
Confidencialidad , Recolección de Datos/ética , Investigación sobre Servicios de Salud/ética , Difusión de la Información/ética , Consentimiento Informado , Registros Médicos , Privacidad , Seguridad Computacional , Recolección de Datos/legislación & jurisprudencia , Ética en Investigación , Unión Europea , Investigación sobre Servicios de Salud/legislación & jurisprudencia , Humanos , Difusión de la Información/legislación & jurisprudencia , Cooperación Internacional , Control Social Formal
15.
J Med Internet Res ; 19(2): e47, 2017 02 24.
Artículo en Inglés | MEDLINE | ID: mdl-28235748

RESUMEN

BACKGROUND: The enactment of the General Data Protection Regulation (GDPR) will impact on European data science. Particular concerns relating to consent requirements that would severely restrict medical data research have been raised. OBJECTIVE: Our objective is to explain the changes in data protection laws that apply to medical research and to discuss their potential impact. METHODS: Analysis of ethicolegal requirements imposed by the GDPR. RESULTS: The GDPR makes the classification of pseudonymised data as personal data clearer, although it has not been entirely resolved. Biomedical research on personal data where consent has not been obtained must be of substantial public interest. CONCLUSIONS: The GDPR introduces protections for data subjects that aim for consistency across the EU. The proposed changes will make little impact on biomedical data research.


Asunto(s)
Investigación Biomédica/métodos , Seguridad Computacional , Informática/métodos , Proyectos de Investigación , Investigación Biomédica/ética , Humanos , Informática/normas
16.
JMIR Mhealth Uhealth ; 5(2): e17, 2017 Feb 20.
Artículo en Inglés | MEDLINE | ID: mdl-28219878

RESUMEN

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a serious long-term lung disease in which the airflow from the lungs is progressively reduced. By 2030, COPD will become the third cause of mortality and seventh cause of morbidity worldwide. With advances in technology and mobile communications, significant progress in the mobile health (mHealth) sector has been recently observed. Mobile phones with app capabilities (smartphones) are now considered as potential media for the self-management of certain types of diseases such as asthma, cancer, COPD, or cardiovascular diseases. While many mobile apps for patients with COPD are currently found on the market, there is little published material on the effectiveness of most of them, their features, and their adoption in health care settings. OBJECTIVES: The aim of this study was to search the literature for current systems related to COPD and identify any missing links and studies that were carried out to evaluate the effectiveness of COPD mobile apps. In addition, we reviewed existing mHealth apps from different stores in order to identify features that can be considered in the initial design of a COPD support tool to improve health care services and patient outcomes. METHODS: In total, 206 articles related to COPD management systems were identified from different databases. Irrelevant materials and duplicates were excluded. Of those, 38 articles were reviewed to extract important features. We identified 214 apps from online stores. Following exclusion of irrelevant apps, 48 were selected and 20 of them were downloaded to review some of their common features. RESULTS: Our review found that out of the 20 apps downloaded, 13 (65%, 13/20) had an education section, 5 (25%, 5/20) consisted of medication and guidelines, 6 (30%, 6/20) included a calendar or diary and other features such as reminders or symptom tracking. There was little published material on the effectiveness of the identified COPD apps. Features such as (1) a social networking tool; (2) personalized education; (3) feedback; (4) e-coaching; and (5) psychological motivation to enhance behavioral change were found to be missing in many of the downloaded apps. CONCLUSIONS: This paper summarizes the features of a COPD patient-support mobile app that can be taken into consideration for the initial design of an integrated care system to encourage the self-management of their condition at home.

17.
J Glaucoma ; 26(3): 233-240, 2017 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-27906810

RESUMEN

PURPOSE: The measurement of intraocular pressure (IOP) by Goldmann applanation tonometry (GAT) is based on assumptions about corneal parameters. To correct for variations in corneal curvature and thickness, a number of equations have been proposed. This study evaluates the in vivo accuracy of these equations from individuals with primary open-angle glaucoma and compared them with measurements taken using the Pascal dynamic contour tonometer (DCT), which makes no assumptions about the corneal geometry or biomechanics. PARTICIPANTS AND METHODS: The study included 108 participants with primary open-angle glaucoma (47 male and 61 female) with an age range of 39 to 81 years. Participants were recruited from the Glaucoma Clinic at Wroclaw Medical University. A full ophthalmologic examination was conducted on all participants. Participants were divided into 3 groups depending on IOP as measured by GAT. Six formulae were applied and the results were compared with measurements taken with DCT. MAIN OUTCOME MEASURES: To determine as to which formula provides the closest value to IOP measured with DCT. RESULTS: For IOP values ≤29 mm Hg, 2 of the formulae showed the smallest and comparable mean differences and SDs between corrected IOP values obtained with GAT and those measured with DCT. For IOP≥30 mm Hg, the formula derived from the model of corneal applanation that takes into account corneal buckling showed the closest agreement with measurements taken using DCT. CONCLUSIONS: Correction formulae provide widely varying results and their appropriateness can depend on the IOP values.


Asunto(s)
Glaucoma de Ángulo Abierto/diagnóstico , Presión Intraocular/fisiología , Tonometría Ocular/métodos , Adulto , Anciano , Anciano de 80 o más Años , Análisis de Varianza , Córnea/anatomía & histología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Modelos Teóricos
18.
Oxid Med Cell Longev ; 2016: 3240261, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-27822337

RESUMEN

Purpose. L-Carnosine is a naturally occurring dipeptide which recently gained popularity as an anticataractogenic agent due to its purported antioxidant activities. There is a paucity of research and conclusive evidence to support such claims. This work offers compelling data that help clarify the mechanism(s) behind the anticataract properties of L-carnosine. Methods. Direct in vitro antioxidant free radical scavenging properties were assayed using three different antioxidant (TEAC, CUPRAC, and DPPH) assays. Indirect in vitro and ex vivo antioxidant assays were studied by measuring glutathione bleaching capacity and total sulfhydryl (SH) capacity of bovine lens homogenates as well as hydrogen-peroxide-stress assay using human lens epithelial cells. Whole porcine lenses were incubated in high galactose media to study the anticataract effects of L-carnosine. MTT cytotoxicity assays were conducted on human lens epithelial cells. Results. The results showed that L-carnosine is a highly potent antiglycating agent but with weak metal chelating and antioxidant properties. There were no significant decreases in lens epithelial cell viability compared to negative controls. Whole porcine lenses incubated in high galactose media and treated with 20 mM L-carnosine showed a dramatic inhibition of advanced glycation end product formation as evidenced by NBT and boronate affinity chromatography assays. Conclusion. L-Carnosine offers prospects for investigating new methods of treatment for diabetic cataract and any diseases that are caused by glycation.


Asunto(s)
Carnosina/uso terapéutico , Catarata/prevención & control , Antioxidantes , Carnosina/administración & dosificación , Quelantes/farmacología , Humanos , Cristalino/efectos de los fármacos
19.
Int J Chron Obstruct Pulmon Dis ; 11: 2831-2838, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-27881915

RESUMEN

BACKGROUND: COPD is among the leading causes of chronic morbidity and mortality in the European Union with an estimated annual economic burden of €25.1 billion. Various care pathways for COPD exist across Europe leading to different responses to similar problems. Determining these differences and the similarities may improve health and the functioning of health services. OBJECTIVE: The aim of this study was to compare COPD patients' care pathway in five European Union countries including England, Ireland, the Netherlands, Greece, and Germany and to explore health care professionals' (HCPs) perceptions about the current pathways. METHODS: HCPs were interviewed in two stages using a qualitative, semistructured email interview and a face-to-face semistructured interview. RESULTS: Lack of communication among different health care providers managing COPD and comorbidities was a common feature of the studied care pathways. General practitioners/family doctors are responsible for liaising between different teams/services, except in Greece where this is done through pulmonologists. Ireland and the UK are the only countries with services for patients at home to shorten unnecessary hospital stay. HCPs emphasized lack of communication, limited resources, and poor patient engagement as issues in the current pathways. Furthermore, no specified role exists for pharmacists and informal carers. CONCLUSION: Service and professional integration between care settings using a unified system targeting COPD and comorbidities is a priority. Better communication between health care providers, establishing a clear role for informal carers, and enhancing patients' engagement could optimize current care pathways resulting in a better integrated system.


Asunto(s)
Actitud del Personal de Salud , Vías Clínicas , Prestación Integrada de Atención de Salud , Disparidades en Atención de Salud , Grupo de Atención al Paciente , Percepción , Pautas de la Práctica en Medicina , Enfermedad Pulmonar Obstructiva Crónica/terapia , Conducta Cooperativa , Vías Clínicas/tendencias , Prestación Integrada de Atención de Salud/tendencias , Europa (Continente)/epidemiología , Unión Europea , Encuestas de Atención de la Salud , Disparidades en Atención de Salud/tendencias , Humanos , Comunicación Interdisciplinaria , Entrevistas como Asunto , Grupo de Atención al Paciente/tendencias , Pautas de la Práctica en Medicina/tendencias , Prevalencia , Enfermedad Pulmonar Obstructiva Crónica/diagnóstico , Enfermedad Pulmonar Obstructiva Crónica/epidemiología , Enfermedad Pulmonar Obstructiva Crónica/fisiopatología , Investigación Cualitativa
20.
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA