Diffusion-based design of multi-layered ophthalmic lenses for controlled drug release

The study of ocular drug delivery systems has been one of the most covered topics in drug delivery research. One potential drug carrier solution is the use of materials that are already commercially available in ophthalmic lenses for the correction of refractive errors. In this study, we present a diffusion-based mathematical model in which the parameters can be adjusted based on experimental results obtained under controlled conditions. The model allows for the design of multi-layered therapeutic ophthalmic lenses for controlled drug delivery. We show that the proper combination of materials with adequate drug diffusion coefficients, thicknesses and interfacial transport characteristics allows for the control of the delivery of drugs from multi-layered ophthalmic lenses, such that drug bursts can be minimized, and the release time can be maximized. As far as we know, this combination of a mathematical modelling approach with experimental validation of non-constant activity source lamellar structures, made of layers of different materials, accounting for the interface resistance to the drug diffusion, is a novel approach to the design of drug loaded multi-layered contact lenses.info:eu-repo/semantics/publishedVersio

Numerical implementation of generalized Coddington equations for ophthalmic lens design

Postprint (author's final draft

The fabrication of ophthalmic lenses

A comprehensive description of the manufacturing process of ophthalmic lenses is presented. Text is presented along with photographs that depict each step in the manufacturing process. This paper is intended to be used as a teaching manual or handout in the optometric curriculum so that future Optometrists my become more familiar with this most important subject

Controlled drug delivery from ophthalmic lenses

Poster apresentado no Ciência 2016 – Encontro com a Ciência e Tecnologia em Portugal. Centro de Congressos de Lisboa, 4-6 julho 2016N/

Effects of magnification and visual accommodation on aimpoint estimation in simulated landings with real and virtual image displays

Twenty professional pilots observed a computer-generated airport scene during simulated autopilot-coupled night landing approaches and at two points (20 sec and 10 sec before touchdown) judged whether the airplane would undershoot or overshoot the aimpoint. Visual accommodation was continuously measured using an automatic infrared optometer. Experimental variables included approach slope angle, display magnification, visual focus demand (using ophthalmic lenses), and presentation of the display as either a real (direct view) or a virtual (collimated) image. Aimpoint judgments shifted predictably with actual approach slope and display magnification. Both pilot judgments and measured accommodation interacted with focus demand with real-image displays but not with virtual-image displays. With either type of display, measured accommodation lagged far behind focus demand and was reliably less responsive to the virtual images. Pilot judgments shifted dramatically from an overwhelming perceived-overshoot bias 20 sec before touchdown to a reliable undershoot bias 10 sec later

Spectral radiance of blue light filters on ophthalmic lenses

As a result of the recent improvement in light-emitting diode (LED) technology, the displays of the vast majority of electronic devices are now illuminated by LEDs. There are several advantages of this type of light source over its predecessors; however, recent research is giving support to the fact that prolonged exposition to the white LEDs emission in the blue spectrum may have a negative impact on visual health, as well as, on biological rhythms (circadian rhythms). As a consequence, ophthalmic lens manufacturers have recently introduced in the market innovative lenses that incorporate blue light filters, especially designed for electronic device users. In this work, the performance of different blue light filters present on commercially available ophthalmic lenses was tested and compared. Lenses were placed in front of a LED-based backlight tablet, in a similar way a common user would be reading a text on the electronic device. The absorption characteristics of the various samples from four different ophthalmic lens manufacturers were measured. Analysis of the different samples from the same manufacturer was conducted and blue light filters from different manufacturers were compared. © Sociedad Española de Óptica.Postprint (published version

International trade between Spain-Morocco-Portugal: are there any opportunities for optical products?

This paper deals with the international trade interrelations between Spain and its closest neighbours to the South and West: Portugal and Morocco. It analyses the importance of optical products in the trade balance with those countries. To do so, a Social Accounting Matrix for Spain is used as a benchmark economic model, where the optical sector has been disaggregated and international coefficients are considered in order to include the effect of Portugal and Morocco in the Spanish economic system. Results show that, although Portugal plays a considerably important role, there are still growth opportunities toward the relations with Morocco.Este trabajo trata sobre las relaciones internacionales entre España y sus vecinos más cercanos al sur y oeste: Portugal y Marruecos, analizando la importancia de los productos ópticos en la balanza con dichos países. Para ello, se hace uso de la Matriz de Contabilidad Social para España como modelo económico de referencia, donde el sector óptico aparece desagregado, además se consideran coeficientes internacionales con la finalidad de incluir el efecto de Portugal y Marruecos en el sistema económico español. Los resultados muestran que, a pesar de que Portugal ocupa una posición considerablemente importante, aún existen amplias oportunidades de crecimiento en las relaciones hacia Marruecos

Metodología para evaluar efectos del deslumbramiento en amétropes corregidos

Light originated at a glare source and entering the eye, produces a veiling luminance that causes contrast decrease in retinal images and this effect could differ if the subject wears lenses or not. In this work the glare effects in subjects wearing lenses is studied inducing ammetropies in emmetropes. Contrast thresholds of sinusoidal patterns of 2 cpd and 0.5 cd/m2 are evaluated without and with glare, the glare source being steady, at 12o and producing 60 lx at the cornea. To exemplify the use of this methodology, 2 emmetropes under 8 different conditions are considered: naked eye; 3 control conditions (wearing neutral lenses) and 4 ammetropic conditions, inducing low (2 D) and medium (5 D) myopia and hyperopia with positive and negative contact lenses and correcting them with adequate ophthalmic lenses. The contrast threshold differences between the naked eye and the other 7 conditions are statistically not significant without glare and significant (up to more than 100%) with glare, independently of lens power and probably due to ectopic scattering and multiple reflections. The method proposed enables the determination of the glare effects if lenses are worn though a greater population is required to attain conclusive data.La luz originada en una fuente deslumbrante que entra al ojo, produce una luminancia de velo que causa una disminución de contraste en las imágenes retinianas y este efecto podría diferir si el sujeto usa lentes o no. En este trabajo se estudian los efectos del deslumbramiento en sujetos que usan lentes induciendo ametropías en emétropes. Se evalúan contrastes umbrales de patrones sinusoidales de 2 cpd y 0.5 cd/m2 sin y con deslumbramiento, la fuente deslumbrante siendo estable, a 12º y produciendo 60 lx en la córnea. Para ejemplificar el uso de esta metodología, se consideran 2 emétropes en 8 condiciones diferentes: ojo desnudo; 3 condiciones de control (lentes neutras) y 4 condiciones ametrópicas, induciendo miopía e hipermetropía baja (±2 D) y media (±5 D) con lentes de contacto positivas y negativas y corrigiéndolas con adecuadas lentes oftálmicas. Las diferencias de contraste entre el ojo desnudo y las otras 7 condiciones son estadísticamente no significativas sin deslumbramiento y significativas (hasta más de 100%) con deslumbramiento, independientemente de la potencia de la lente y probablemente debido a scattering ectópico y reflexiones múltiples. El método propuesto permite determinar los efectos de deslumbramiento al usar lentes aunque, para tener datos contundentes, se requiere una mayor poblaciónFil: de Paul Camacho, Anibal Gabriel. Universidad Nacional de Tucuman. Facultad de Cs.exactas y Tecnologia. Departamento de Luminotecnia, Luz y Vision; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucuman. Instituto de Investigacion En Luz, Ambiente y Vision; ArgentinaFil: Colombo, Elisa Margarita. Universidad Nacional de Tucuman. Facultad de Cs.exactas y Tecnologia. Departamento de Luminotecnia, Luz y Vision; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucuman. Instituto de Investigacion En Luz, Ambiente y Vision; ArgentinaFil: Comastri, Silvia Ana Elva. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingenieria. Departamento de Fisica; ArgentinaFil: Aparicio, Juan A.. Universidad de Valladolid. Facultad de Ciencias; EspañaFil: Menéndez, José Antonio. Universidad de Valladolid. Facultad de Ciencias; EspañaFil: Issolio, Luis Alberto. Universidad Nacional de Tucuman. Facultad de Cs.exactas y Tecnologia. Departamento de Luminotecnia, Luz y Vision; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucuman. Instituto de Investigacion En Luz, Ambiente y Vision; Argentin