Oblique surface waves at an interface between a metal–dielectric superlattice and an isotropic dielectric

We investigate the existence and dispersion characteristics of surface waves that propagate at an interface between a metal–dielectric superlattice and an isotropic dielectric. Within the long-wavelength limit, when the effective-medium (EM) approximation is valid, the superlattice behaves like a uniaxial plasmonic crystal with the main optical axes perpendicular to the metal–dielectric interfaces. We demonstrate that if such a semi-infinite plasmonic crystal is cut normally to the layer interfaces and brought into contact with a semi-infinite dielectric, a new type of surface mode can appear. Such modes can propagate obliquely to the optical axes if favorable conditions regarding the thickness of the layers and the dielectric permittivities of the constituent materials are met. We show that losses within the metallic layers can be substantially reduced by making the layers sufficiently thin. At the same time, a dramatic enlargement of the range of angles for oblique propagation of the new surface modes is observed. This can lead, however, to field non-locality and consequently to failure of the EM approximation.

Substantial enlargement of angular existence range for Dyakonov-like surface waves at semi-infinite metal-dielectric superlattice

We investigated surface waves guided by the boundary of a semi-infinite layered metal-dielectric nanostructure cut normally to the layers and a semi-infinite dielectric material. Using the Floquet-Bloch formalism, we found that Dyakonov-like surface waves with hybrid polarization can propagate in dramatically enhanced angular range compared to conventional birefringent materials. Our numerical simulations for an Ag-GaAs stack in contact with glass show a low to moderate influence of losses.

Inconsistencies in Guidelines for Visual Health Surveillance of VDT Workers

Objectives: In Europe, 25% of workers use video display terminals (VDTs). Occupational health surveillance has been considered a key element in the protection of these workers. Nevertheless, it is unclear if guidelines available for this purpose, based on EU standards and available evidence, meet currently accepted quality criteria. The aim of this study was to appraise three sets of European VDT guidelines (UK, France, Spain) in which regulatory and evidence-based approaches for visual health have been formulated and recommendations for practice made. Methods: Three independent appraisers used an adapted AGREE instrument with seven domains to appraise the guidelines. A modified nominal group technique approach was used in two consecutive phases: first, individual evaluation of the three guidelines simultaneously, and second, a face-to-face meeting of appraisers to discuss scoring. Analysis of ratings obtained in each domain and variability among appraisers was undertaken (correlation and kappa coefficients). Results: All guidelines had low domain scores. The domain evaluated most highly was Scope and purpose, while Applicability was scored minimally. The UK guidelines had the highest overall score, and the Spanish ones had the lowest. The analysis of reliability and differences between scores in each domain showed a high level of agreement. Conclusions: These results suggest current guidelines used in these countries need an update. The formulation of evidence-base European guidelines on VDT could help to reduce the significant variation of national guidelines, which may have an impact on practical application.

Caracterización clínica y anatómica del segmento anterior mediante tecnología de cámara Scheimpflug en un caso de lenticono posterior

Presentamos un caso de pérdida de agudeza visual unilateral no explicable por factores corneales o retinianos en el que se detecta un lenticono posterior mediante tecnología de cámara Scheimpflug. En concreto, se trata de una paciente de 7 años de edad que acude con una disminución de la agudeza visual del ojo derecho desde hacía tres años. La agudeza visual del ojo derecho en lejos es de 0,3 con la mejor corrección y de cerca de 0,8. Se observaron reflejos retinoscópicos en tijera, así como la presencia de una pequeña opacidad lenticular polar posterior mediante biomicroscopía. No tenía antecedentes de patología ocular ni presentaba ninguna alteración compatible con el síndrome de Alport o el síndrome de Morning Glory, así como tampoco presentaba ningún tipo de alergia. Mediante un análisis con un sistema basado en tecnología de cámara Scheimpflug se pudo detectar un encurvamiento de la cara posterior del cristalino, confirmando el diagnóstico de lenticono posterior. La pérdida visual puede ser debida a que el lenticono se encuentra en la zona paracentral del cristalino, pudiendo también contribuir la opacidad congénita del cristalino. En conclusión, el ópticooptometrista, como primer eslabón en la atención visual primaria, puede pensar en el potencial diagnóstico de lenticono cuando no existe una pérdida de agudeza visual sin causa corneal, retiniana o refractiva que lo justifique, siendo la tecnología de cámara Scheimpflug muy útil para la confirmación del diagnóstico.

Adaptación de lente de contacto cosmética en un caso de midriasis máxima irrefléxica y estrabismo tras cirugía complicada de cataratas

Se presenta un caso clínico con solución de lente de contacto cosmética para una paciente con midriasis máxima irrefléxica provocada por una complicación en cirugía de cataratas. El caso se complica al tener la paciente, además, una endo e hipertropía en ojo izquierdo (OI). Se realiza un estudio optométrico y contactológico en profundidad para establecer la idoneidad del tratamiento elegido y la solución propuesta y aceptada, que es la de adaptar una LC de material biocompatible y trabajada artesanalmente. Con ella se consigue un resultado muy natural y nos aseguramos que el material respeta por completo la fisiología del ojo. Después de una serie de pruebas adaptativas se consigue dotar a la paciente de la comodidad y similitud facial inicialmente consideradas en la primera visita, quedando así subsanada estéticamente esta atrofia ocular inicial.

Retinal microglia are activated by systemic fungal infection

Purpose: To determine whether systemic fungal infection could cause activation of retinal microglia and therefore could be potentially harmful for patients with retinal degenerative diseases. Methods: Activation of retinal microglia was measured in a model of sublethal invasive candidiasis in C57BL/6J mice by (i) confocal immunofluorescence and (ii) flow cytometry analysis, using anti-CD11b, anti-Iba1, anti-MHCII and anti-CD45 antibodies. Results: Systemic fungal infection causes activation of retinal microglia, with phenotypic changes in morphology, surface markers expression, and microglial re-location in retinal layers. Conclusions: As an excessive or prolonged microglial activation may lead to chronic inflammation with severe pathological side effects, causing or worsening the course of retinal dystrophies, a systemic infection may represent a risk factor to be considered in patients with ocular neurodegenerative diseases, such as diabetic retinopathy, glaucoma, age-related macular degeneration or retinitis pigmentosa.

Ocular residual astigmatism and topographic disparity vector indexes in normal healthy eyes

Purpose: To define a range of normality for the vectorial parameters Ocular Residual Astigmatism (ORA) and topography disparity (TD) and to evaluate their relationship with visual, refractive, anterior and posterior corneal curvature, pachymetric and corneal volume data in normal healthy eyes. Methods: This study comprised a total of 101 consecutive normal healthy eyes of 101 patients ranging in age from 15 to 64 years old. In all cases, a complete corneal analysis was performed using a Scheimpflug photography-based topography system (Pentacam system Oculus Optikgeräte GmbH). Anterior corneal topographic data were imported from the Pentacam system to the iASSORT software (ASSORT Pty. Ltd.), which allowed the calculation of the ocular residual astigmatism (ORA) and topography disparity (TD). Linear regression analysis was used for obtaining a linear expression relating ORA and posterior corneal astigmatism (PCA). Results: Mean magnitude of ORA was 0.79 D (SD: 0.43), with a normality range from 0 to 1.63 D. 90 eyes (89.1%) showed against-the-rule ORA. A weak although statistically significant correlation was found between the magnitudes of posterior corneal astigmatism and ORA (r = 0.34, p < 0.01). Regression analysis showed the presence of a linear relationship between these two variables, although with a very limited predictability (R2: 0.08). Mean magnitude of TD was 0.89 D (SD: 0.50), with a normality range from 0 to 1.87 D. Conclusion: The magnitude of the vector parameters ORA and TD is lower than 1.9 D in the healthy human eye.

In vivo characterization of corneal biomechanics

Interest in corneal biomechanics has increased with the development of new refractive surgery techniques aimed at modifying corneal properties and a variety of surgical options for corneal ectasia management. The human cornea behaves as soft biological material. It is a viscoelastic tissue and its response to a force applied to it depends not only on the magnitude of the force, but also on the velocity of the application. There are concerns about the limitations to measuring corneal biomechanical properties in vivo. To date, 2 systems are available for clinical use: the Ocular Response Analyzer, a dynamic bidirectional applanation device, and the Corvis ST, a dynamic Scheimpflug analyzer device. These devices are useful in clinical practice, especially for planning some surgical procedures and earlier detection of ectatic conditions, but further research is needed to connect the clinical measurements obtained with these devices to the standard mechanical properties.

Surgical outcomes of isolated lens coloboma with or without cataract among young adults

Objective: To evaluate the visual and refractive outcomes after phacoemulsification surgery in eyes with isolated lens coloboma. Design: Prospective, consecutive case series. Participants: Eighteen eyes with isolated lens coloboma of 13 patients were included in the study. Mean patient age was 13.9 ± 6.5 years. Methods: Patients underwent phacoemulsification surgery, with combined implantation of capsular tension ring (CTR) and intraocular lens. In colobomas of less than 120°, a CTR was used, whereas in colobomas of more than 120°, a Cionni-modified single eyelet CTR was used to achieve better capsular centration. The main outcome measures were uncorrected distance visual acuity, corrected distance visual acuity, refraction, and keratometry. Results: Mean logMAR uncorrected distance visual acuity and corrected distance visual acuity improved significantly from 1.53 ± 0.35 and 1.02 ± 0.47 before surgery to 0.67 ± 0.51 and 0.52 ± 0.49 at the last visit of the follow-up (p < 0.001). Mean refractive cylinder and spherical equivalent decreased significantly from –6.73 ± 1.73 and –6.72 ± 4.07 D preoperatively to –1.40 ± 1.39 and –0.83 ± 1.31 D at the end of the follow-up (p = 0.001 and p = 0.01, respectively). Mean keratometric astigmatism at preoperative and postoperative visits were 1.58 ± 0.97 and 1.65 ± 0.94 D, respectively (p = 0.70). Conclusions: Phacoemulsification with CTR and intraocular lens implantation is an effective and safe option for providing a refractive correction and a significant visual improvement in eyes with isolated lens coloboma.

In vitro differentiation of murine hematopoietic progenitor cells toward the myeloid lineage occurs in response to Staphylococcus aureus and yeast species

We have studied the effect of inactivated microbial stimuli (Candida albicans, Candida glabrata, Saccharomyces boulardii, and Staphylococcus aureus) on the in vitro differentiation of lineage negative (Lin−) hematopoietic progenitor mouse cells. Purified Lin− progenitors were co-cultured for 7 days with the stimuli, and cell differentiation was determined by flow cytometry analysis. All the stimuli assayed caused differentiation toward the myeloid lineage. S. boulardii and particularly C. glabrata were the stimuli that induced in a minor extent differentiation of Lin− cells, as the major population of differentiated cells corresponded to monocytes, whereas C. albicans and S. aureus induced differentiation beyond monocytes: to monocyte-derived dendritic cells and macrophages, respectively. Interestingly, signaling through TLR2 by its pure ligand Pam3CSK4 directed differentiation of Lin− cells almost exclusively to macrophages. These data support the notion that hematopoiesis can be modulated in response to microbial stimuli in a pathogen-dependent manner, being determined by the pathogen-associated molecular patterns and the pattern-recognition receptors involved, in order to generate the populations of mature cells required to deal with the pathogen.

Is there any evidence for the validity of diagnostic criteria used for accommodative and nonstrabismic binocular dysfunctions?

Purpose: To analyze the diagnostic criteria used in the scientific literature published in the past 25 years for accommodative and nonstrabismic binocular dysfunctions and to explore if the epidemiological analysis of diagnostic validity has been used to propose which clinical criteria should be used for diagnostic purposes. Methods: We carried out a systematic review of papers on accommodative and non-strabic binocular disorders published from 1986 to 2012 analysing the MEDLINE, CINAHL, PsycINFO and FRANCIS databases. We admitted original articles about diagnosis of these anomalies in any population. We identified 839 articles and 12 studies were included. The quality of included articles was assessed using the QUADAS-2 tool. Results: The review shows a wide range of clinical signs and cut-off points between authors. Only 3 studies (regarding accommodative anomalies) assessed diagnostic accuracy of clinical signs. Their results suggest using the accommodative amplitude and monocular accommodative facility for diagnosing accommodative insufficiency and a high positive relative accommodation for accommodative excess. The remaining 9 articles did not analyze diagnostic accuracy, assessing a diagnosis with the criteria the authors considered. We also found differences between studies in the way of considering patients’ symptomatology. 3 studies of 12 analyzed, performed a validation of a symptom survey used for convergence insufficiency. Conclusions: Scientific literature reveals differences between authors according to diagnostic criteria for accommodative and nonstrabismic binocular dysfunctions. Diagnostic accuracy studies show that there is only certain evidence for accommodative conditions. For binocular anomalies there is only evidence about a validated questionnaire for convergence insufficiency with no data of diagnostic accuracy.

Alteraciones oculares y visuales en personas que trabajan con ordenador y son usuarias de lentes de contacto: una revisión bibliográfica

Fundamentos: El elevado número de personas que trabajando con ordenador utiliza lentes de contacto plantea la cuestión sobre si la suma de estos dos factores de riesgo para la salud visual puede originar un agravamiento del Síndrome Visual Informático. El objetivo de esta revisión es sintetizar el conocimiento científico sobre las alteraciones oculares y visuales relacionadas con la exposición a ordenador en usuarios de lentes de contacto. Métodos: Revisión de artículos científicos (2003-2013) en español e inglés, realizando una búsqueda bibliográfica, en Medline a través de PubMed y en Scopus. Resultados: La búsqueda inicial aportó 114 trabajos, después de aplicar criterios de inclusión/exclusión se incluyeron seis artículos. Todos ellos ponen de manifiesto que las alteraciones al utilizar el ordenador son más frecuentes en las personas usuarias de lentes de contacto, con prevalencias que oscilan de 95,0% al 16,9% que en las que no utilizan lentes de contacto, cuya prevalencia va del 57,5% al 9,9% y con una probabilidad cuatro veces mayor de padecer ojo seco [OR: 4,07 (IC 95%: 3,52-4,71)]. Conclusiones: Las personas usuarias de ordenador padecen más alteraciones oculares y visuales cuando además son usuarias de lentes de contacto, pero los estudios son escasos y poco contundentes. Se precisan nuevas investigaciones que analicen la influencia según los tipos de lentes y sus condiciones de uso, tanto en la sintomatología como en la calidad de la lágrima y la superficie ocular. Las lentes de hidrogel de silicona son las que se asocian a mayor confort.

Clinical and quality of life data correlation with a single-optic accommodating intraocular lens

Purpose: To examine a single-optic accommodating intraocular lens (IOL) visual performance by correlating IOL implanted eyes’ defocus curve with the intraocular aberrometric profile and the impact on the quality of life (QOL). Methods: Prospective consecutive case series study including a total of 25 eyes of 14 patients with ages ranging between 52 and 79 years old. All cases underwent cataract surgery with implantation of the single-optic accommodating IOL Crystalens HD (Bausch & Lomb). Distance and near visual acuity outcomes, intraocular aberrations, the defocus curve and QOL (NEI VFQ-25) were evaluated 3 months after surgery. Results: A significant improvement in distance visual acuity was found postoperatively (p = 0.02). Mean postoperative LogMAR uncorrected near visual acuity was 0.44 ± 0.23 (20/30). 60% of eyes had a postoperative addition between 0 and 1.5 diopters (D). The defocus curve showed an area of maximum visual acuity for the levels of defocus corresponding to distance and intermediate vision (−1 to +0.5 D). Postoperative intermediate visual acuity correlated significantly some QOL indices (r ≥ 0.51, p ≤ 0.03; difficulty in going down steps or seeing how people react to things that patient says) as well as with J0 component of manifest cylinder. Postoperative distance-corrected near visual acuity correlated significantly with age (r = 0.65, p < 0.01). Conclusions: This accommodating IOL seems to be able to restore the distance visual function as well as to provide an improvement in intermediate and near vision with a significant impact on patient's QOL, although limited by age and astigmatism. Future studies with larger sample sizes should confirm all these trends.