A. López-Alemany - Academia.edu (original) (raw)
Papers by A. López-Alemany
Ophthalmic and Physiological Optics, 2006
Purpose: The purpose of the present study was to measure equilibrium water content (EWC) and ref... more Purpose: The purpose of the present study was to measure equilibrium water content (EWC) and refractive index of conventional and silicone hydrogel soft contact lenses (SCL) using a hand refractometer and an automated refractometer.Methods: Sixteen SCL were used in this study including 12 conventional SCL not containing siloxane moieties (equilibrium water content (EWC) range: 38.6–74%) and the four silicone hydrogel based contact lenses currently available (WC range: 24–47%). Two experienced observers performed the measurements in a randomised order being masked by a third party during the three sessions at which the measurements were collected. The Atago N‐2E hand refractometer and the CLR 12‐70 digital refractometer were used. Data were analysed separately for conventional and silicone hydrogel materials.Results: Measured EWC and refractive index correlate better when measured with the instruments used in this study (r2 = 0.979, p < 0.001) than the nominal parameters (r2 = ...
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2006
In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses wer... more In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses were observed by atomic force microscopy (AFM) in tapping mode at areas ranging from 0.25 to 400 microm2. Mean roughness (Ra), root-mean-square roughness (Rms) and maximum roughness (Rmax) in nanometers were obtained for the three lens materials at different magnifications. The three contact lenses showed significantly different surface topography. However, roughness values were dependent of the surface area to be analyzed. For a 1 microm2 area, statistics revealed a significantly more irregular surface of balafilcon A (Ra = 6.44 nm; Rms = 8.30 nm; Rmax = 96.82 nm) compared with lotrafilcon A (Ra = 2.40 nm; Rms = 3.19 nm; Rmax = 40.89 nm) and galyfilcon A (Ra = 1.40 nm; Rms = 1.79 nm; Rmax = 15.33 nm). Ra and Rms were the most consistent parameters, with Rmax presenting more variability for larger surface areas. The higher roughness of balafilcon A is attributed to the plasma oxidation treatment used to improve wettability. Conversely, galyfilcon A displays a smoother surface. Present observations could have implications in clinical aspects of siloxane-hydrogel contact lens wear such as lens spoliation, resistance to bacterial adhesion, or mechanical interaction with the ocular surface.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2006
The purpose of this study was to analyze three commercial siloxane-hydrogel contact lens material... more The purpose of this study was to analyze three commercial siloxane-hydrogel contact lens materials, lotrafilcon A, balafilcon A, and galyfilcon A, by cryogenic scanning electron microscopy (cryoSEM). The fully hydrated lenses were frozen in slush liquid nitrogen and qualitatively observed in a cryogenic scanning electron microscope. The superficial ultrastructure of the siloxane-hydrogels was observed at the areas where the lens fractured during sample cryogenic preparation. There are qualitative differences among the three examined materials in the complex polymer network structure existing between the outer layer and the underlying polymer. CryoSEM, although destructive, is a useful tool to investigate the structure of polymers used in contact lenses. This technique allows the observation of the inner structure of polymers in the hydrated state. The ultrastructure, the polymer network underlying the outer surface of siloxane-hydrogels by cryoSEM microscopy, have never been reported before.
Journal of Applied Polymer Science, 1999
To test the validity of the method of stacked hydrogel contact lenses to obtain the oxygen permea... more To test the validity of the method of stacked hydrogel contact lenses to obtain the oxygen permeability and transmissibility coefficients of the lenses, the coefficients of one low hydration (38% water) and two high hydration (55 and 58% water) hydrogel contact lenses stacked one to five on an oxygen electrode were determined. From the oxygen diffusion through the lenses, the current intensity in the stationary state was determined, and from this the "instrument" the oxygen transmissibility was obtained. The permeability coefficients of the lenses, corrected for edge effects, were obtained from the slope of the plot of the reciprocal of the transmissibility coefficients versus the lens thicknesses. The oxygen permeability and transmissibility coefficients of the lenses obtained neglected the boundary layers resistance between the stacked lenses and, therefore, these are not the "true" coefficients. This article compares the "apparent" oxygen permeability coefficients of the hydrogel contact lenses, obtained by others, with the "true" oxygen permeability coefficients obtained with a corrected equation that takes into account the boundary layers between the stacked lenses.
Journal of Biomedical Materials Research, 2002
The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevi... more The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevisiontrade mark (balafilcon A) and Focus(R)Night&amp;amp;amp;amp;amp;amp;amp;amp;Daytrade mark (lotrafilcon A), were investigated. Standard hydrogel lenses of low (Seequence(R)), medium (Acuvue(R)), and high water content (Precision UV(R)) were used as controls. All the lenses were dehydrated in a series of ethanol solutions of increased concentration, critical-point dried in CO(2), and sputter coated with gold/palladium before they were examined by scanning electron microscopy. Of all lenses examined, only the balafilcon lenses presented, in addition to the polymer network porosity characteristic of all hydrogels, a macroporous structure that was observed on the front and back surfaces, and in their bulk. The average diameter of the macropores appears to be much larger, from one to several orders of magnitude, than the network porosity of standard hydrogel lenses. The macropores might contribute to the gas and water permeability of these lenses, as well as to their mobility on the cornea.
Journal of the American Optometric Association, 1999
BACKGROUND In this study, we evaluated the pH value of nine artificial tears solutions in order t... more BACKGROUND In this study, we evaluated the pH value of nine artificial tears solutions in order to investigate whether their pH changed over time. These solutions are designed to have a pH value within the ocular comfort range and to come close to the physiological tears' pH. METHODS Fifteen bottles of each solution were randomly chosen from different production lots. Increments of 0.05 ml were taken daily from each bottle and measured daily, using a micropH 2002 Crison pH-meter over a period of 60 days. RESULTS The values obtained fall within the ocular comfort range. Also, we obtained nonstatistically significant variations over time for each solution (p > 0.01). The results revealed differences between solutions, some solutions coming close to the tear's pH and others being slightly more acidic or alkaline. CONCLUSIONS We may assume that all the solutions evaluated will not affect either the ocular physiology or the contact lens wear. The practitioners should know the ...
Archivos de la Sociedad Española de Oftalmología
confirmados de COVID-19. Deberán ser adaptadas a las circunstancias y disponibilidad de equipos d... more confirmados de COVID-19. Deberán ser adaptadas a las circunstancias y disponibilidad de equipos de protección individual en cada uno de los centros y Comunidades Autónomas, debiendo ser actualizadas en función de las fases de la pandemia y de las medidas que adopte el Gobierno de la nación. Conclusiones: Durante la pandemia COVID-19, la atención a los potenciales riesgos de salud para la población ocasionados por el coronavirus deberá prevalecer sobre la posible progresión de enfermedades oculares comunes. Tanto médicos oftalmólogos como restantes profesionales de la salud ocular deberán asumir una posible progresión de dichas enfermedades ante la imposibilidad de un seguimiento adecuado de los pacientes.
Archivos de la Sociedad Española de Oftalmología (English Edition)
Objective: Minimize exposure to the SARS-CoV-2, reduce the chances of cross-transmission between ... more Objective: Minimize exposure to the SARS-CoV-2, reduce the chances of cross-transmission between patients and healthcare personnel, and prevent the development of postoperative complications from the management of patients with eye diseases during the 2019 coronavirus disease pandemic (COVID-19). Methods: COVID-19 literature review and consensus establishment between different Spanish ophthalmology societies in order to provide guidelines and recommendations of maximum resources primarily conditioned by the state of alert, confinement and social distancing that occurs in Spain since March 16, 2020. Results: The recommendations will promote the adoption of action and protection measures for eye care in outpatient clinics, surgical areas and hospitalization, for unconfirmed (asymptomatic and symptomatic) and confirmed COVID-19 patients. Measures must be adapted to the circumstances and availability of personal protective equipment in each of the centers
espanolObjetivo: Estudio de la transmisibilidad a los gases de lentes de contacto hidrofilas (LCH... more espanolObjetivo: Estudio de la transmisibilidad a los gases de lentes de contacto hidrofilas (LCH) multifocales disponibles en el mercado. Material y metodos: Con sonda polarografica acoplada a un permeometro se tomaron cinco medidas de transmisibilidad, en cinco LCH de 38%, 49%, 55%, 58% Y 73% de hidratacion. Resultados: Se encontraron diferencias cuali-y cuantitativas en el flujo de O₂ a traves de los diferentes materiales, siendo significativas las diferencias entre LCH de hidratacion superior al 50% y LCH de hidratacion inferior. Hubo tendencia de las lentes mas positivas hacia una menor transmisibilidad a los gases. No hubo diferencias significativas en el flujo de gases en relacion con el valor de la adicion, aunque paradojicamente las lentes con mayor adicion tendian a un mayor flujo de O₂. Conclusion: Las LCH de hidratacion media y alta poseen mayor transmisibilidad al Conclusion: Las LCH de hidratacion media y alta poseen mayor transmisibilidad al O₂, lo que es importante en la compensacion multifocal de hipermetropes. Al contrario de lo que sucede con el valor esferico, la adicion parece influir poco en la transmisibilidad, aunque esto varia segun el diseno. EnglishPurpose: Study of transmissibility to gases of on-the-counter multifocal hydrophilic contact lenses (LCH). Material and methods: With a polarographic probe coupled to a permeometer, 5 measures of transmissibility were taken on five LCH of 38%,49%, 55%, 58% and 73% hydration level. Results: Differences in O₂ flow quality and quantity were found through the different materials, being significant the differences between LCH with hydration higher than 50% and LCH of lower hydration. There was a tendency of more positive lenses towards less transmissibility to gases. Not significant differences were found on gas flux in relation to the addition value, although paradoxically, lenses with higher addition values had more oxygen flow. Conclusion: Medium and high water content LCH show more transmissibility to O₂, which is important ton the multifocal compensation of hyperopes. To the contrary of what happens with spherical value, addition seems to influence little on transmissibility, although this varies with the contact lens design.
espanolSe ha medido el contenido de agua de diferentes tipos de lentes hidrofilicas (LCH) utiliza... more espanolSe ha medido el contenido de agua de diferentes tipos de lentes hidrofilicas (LCH) utilizando tres refractometros manuales. El refractometro Atago N-2E es el que permite medir mayor numero de lentes con hidratacion entre 38% y 72%. Para lentes de alta hidratacion (>70%) y de baja hidratacion ( Se obtuvo una alta correlacion entre los valores referidos por el fabricante y los medidos por un observador con experiencia para las LCH convencionales (r²=0,966; p La refractometria manual permite realizar medidas precisas del contenido de agua de las LCH. Es necesario diferenciar claramente entre los materiales de hidrogel de silicona y los materiales de hidrogel convencionales cuando se pretenden medir cambios en el contenido de agua de las diferentes lentes como consecuencia de la utilizacion o para evaluar la capacidad de una LCH para hidratarse con farmacos para su utilizacion terapeutica, puesto que la refractometria manual sobreestima significativamente los valores reales de hidratacion para las LCHS. EnglishIn the present work, the water content of different hydrophilic contact lenses with three different hand-held refractometers has been measured. Atago N2-E allows to measure lenses in the range 32% to 72% water content. Lenses with high water content soft contact lenses (>70%) and low hydration ( A high correlation was found between the values quoted by the manufacturer and those measured by an experienced observer for conventional hydrogel lenses (r²=0.966; p As expected, there was not differences in hydration between positive and negative lenses of the same material (p=0.994), showing an excellent repeatability of the technique measuring different samples of the same material. Investigator’s experience with the technique demonstrated not to affect the variability of the measurements. Hand-held refractometry allows the precise estimation of the water content in hydrophilic soft contact lenses, as confirmed by previous investigations. It’s necessary to differentiate between conventional hydrogel materials and siloxane-hydrogels, as manual refractometry significantly overestimates the hydration ability of materials containing siloxane moieties
espanolObjetivo: Valorar en que medida la seleccion del material de la lente de contacto hidrofil... more espanolObjetivo: Valorar en que medida la seleccion del material de la lente de contacto hidrofila (LCH) y de la lente rigida permeable al gas (LCRPG) influyen en la consecucion del adecuado respeto fisiologico de los sistemas piggyback. Material y metodos: Seis LCH, con permeabilidad entre 8, 5 y 140 barrer, se combinaron con una lente de PMMA impermeable al gas y con tres lentes rigidas permeables al gas (24-189 barrer). Con una sonda polarografica acoplada a un permeometro se realizaron medidas de transmisibilidad, registrandose cinco medidas para cada sistema piggyback. Resultados: La lente de PMMA mostro la permeabilidad mas baja. Todas las demas combinaciones demostraron tener un efecto significativo en la permeabilidad al gas del sistema piggyback. Conclusion: Las lentes de PMMA no son adecuadas para sistemas piggyback. Para la compensacion de irregularidades corneales, por queratocono o queratoplastia con riesgo de neovascularizacion corneal, unicamente debe usarse la combinacion de LCH y LCRPG de alta permeabilidad. EnglishPurpose: Evaluate how selecting the material of a hydrophilic contact lens (HCL) and rigid gas permeable contact lens (RGP) influence the achievement of the appropriate physiological respect of the piggy-back systems. Material and methods: Six HCL, with premeabilities among 8.5 and 140 barrer, were combined with a PMMA contact lens impermeable to gas (24-189 barrer). With a polarographic probe coupled to a permeometer, transmissibility measures were obtained registering five measures for each piggyback system. Results: The PMMA lens showed the lowest permeability. All the remaining combinations showed a significant effect on the permeability to gas of the piggyback system. Conclusion: PMMA lenses are not adequate for piggyback systems. For the compensation of corneal irregularities, keratoconus or keratoplasty with risk of corneal neovascularization, only combinations of HCL and high permeability RGP should be used.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2009
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2007
To investigate the in vitro dehydration process of conventional hydrogel and silicone-hydrogel co... more To investigate the in vitro dehydration process of conventional hydrogel and silicone-hydrogel contact lens materials. Eight conventional hydrogel and five silicone-hydrogel contact lenses were dehydrated under controlled environmental conditions on an analytical balance. Data were taken at 1-min intervals and dehydration curves of cumulative dehydration (CD), valid dehydration (VD), and dehydration rate (DR) were obtained. Several quantitative descriptors of the dehydration process were obtained by further processing of the information. Duration of phase I (r(2) = 0.921), CD at end of phase I (r(2) = 0.971), time to achieve a DR of -1%/min (r(2) = 0.946) were strongly correlated with equilibrium water content (EWC) of the materials. For each individual sample, the VD at different time intervals can be accurately determined using a 2nd order regression equation (r(2) &amp;amp;gt; 0.99 for all samples). The first 5 min of the dehydration process show a relatively uniform average CD of about ...
Journal Français d'Ophtalmologie, 2005
JOURNAL-AMERICAN …, 1999
In this study, we evaluated the pH value of nine artificial tears solutions in order to investiga... more In this study, we evaluated the pH value of nine artificial tears solutions in order to investigate whether their pH changed over time. These solutions are designed to have a pH value within the ocular comfort range and to come close to the physiological tears' pH. Fifteen bottles of each solution were randomly chosen from different production lots. Increments of 0.05 ml were taken daily from each bottle and measured daily, using a micropH 2002 Crison pH-meter over a period of 60 days. The values obtained fall within the ocular comfort range. Also, we obtained nonstatistically significant variations over time for each solution (p > 0.01). The results revealed differences between solutions, some solutions coming close to the tear's pH and others being slightly more acidic or alkaline. We may assume that all the solutions evaluated will not affect either the ocular physiology or the contact lens wear. The practitioners should know the properties of the solutions, thus selecting the adequate solution for each type of patient.
Contact Lens and Anterior Eye, 1998
The pH of nine different brands of multipurpose contact lens solutions available in Spain was det... more The pH of nine different brands of multipurpose contact lens solutions available in Spain was determined over a period of 32 days after opening the bottles. Five bottles of nine solutions were used, each of which was buffered and obtained from different manufacturers. The pH measurements were taken using a micropH 2002 Crison pH-meter (accuracy + O. 001 pH units). Each solution was measured three times daily over the test period using lO-ml samples taken from the same container. Fluctuations in pH over time were observed but these were within the range of ocular comfort. The average pH of all the solutions tested proved to be between 6.99 and 7.56.
Biomaterials, 2004
The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemi... more The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemical procedures, is 5-10 times larger than that of conventional hydrogels. A method is described that allows the estimation of the oxygen tension at the lens-cornea interface for closed-and open-eyelids situations by combining the IOT of the hydrogels and corneal parameters such as corneal thickness, corneal permeability and oxygen flux across the cornea. From these results the biological oxygen apparent transmissibility (BOAT) is obtained, an important parameter which an multiplication with the pressure of oxygen on the external part of the lens gives the oxygen flux onto the cornea. Contact lenses with oxygen transmissibility higher than 100Dk/t units [1Dk/t unit=10 À9 [cm 3 O 2 (STp) cm À2 s À1 (mm Hg) À1 ] posses a large oxygen tension at the lens-cornea interface that substantially reduces the oxygen flux onto the cornea. Lenses whose oxygen transmissibility is lower than 50Dk/t units allow a rather small oxygen flux onto the cornea under closed eyelids condition that prevent their use for extended wear.
Ophthalmic and Physiological Optics, 2006
Purpose: The purpose of the present study was to measure equilibrium water content (EWC) and ref... more Purpose: The purpose of the present study was to measure equilibrium water content (EWC) and refractive index of conventional and silicone hydrogel soft contact lenses (SCL) using a hand refractometer and an automated refractometer.Methods: Sixteen SCL were used in this study including 12 conventional SCL not containing siloxane moieties (equilibrium water content (EWC) range: 38.6–74%) and the four silicone hydrogel based contact lenses currently available (WC range: 24–47%). Two experienced observers performed the measurements in a randomised order being masked by a third party during the three sessions at which the measurements were collected. The Atago N‐2E hand refractometer and the CLR 12‐70 digital refractometer were used. Data were analysed separately for conventional and silicone hydrogel materials.Results: Measured EWC and refractive index correlate better when measured with the instruments used in this study (r2 = 0.979, p < 0.001) than the nominal parameters (r2 = ...
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2006
In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses wer... more In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses were observed by atomic force microscopy (AFM) in tapping mode at areas ranging from 0.25 to 400 microm2. Mean roughness (Ra), root-mean-square roughness (Rms) and maximum roughness (Rmax) in nanometers were obtained for the three lens materials at different magnifications. The three contact lenses showed significantly different surface topography. However, roughness values were dependent of the surface area to be analyzed. For a 1 microm2 area, statistics revealed a significantly more irregular surface of balafilcon A (Ra = 6.44 nm; Rms = 8.30 nm; Rmax = 96.82 nm) compared with lotrafilcon A (Ra = 2.40 nm; Rms = 3.19 nm; Rmax = 40.89 nm) and galyfilcon A (Ra = 1.40 nm; Rms = 1.79 nm; Rmax = 15.33 nm). Ra and Rms were the most consistent parameters, with Rmax presenting more variability for larger surface areas. The higher roughness of balafilcon A is attributed to the plasma oxidation treatment used to improve wettability. Conversely, galyfilcon A displays a smoother surface. Present observations could have implications in clinical aspects of siloxane-hydrogel contact lens wear such as lens spoliation, resistance to bacterial adhesion, or mechanical interaction with the ocular surface.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2006
The purpose of this study was to analyze three commercial siloxane-hydrogel contact lens material... more The purpose of this study was to analyze three commercial siloxane-hydrogel contact lens materials, lotrafilcon A, balafilcon A, and galyfilcon A, by cryogenic scanning electron microscopy (cryoSEM). The fully hydrated lenses were frozen in slush liquid nitrogen and qualitatively observed in a cryogenic scanning electron microscope. The superficial ultrastructure of the siloxane-hydrogels was observed at the areas where the lens fractured during sample cryogenic preparation. There are qualitative differences among the three examined materials in the complex polymer network structure existing between the outer layer and the underlying polymer. CryoSEM, although destructive, is a useful tool to investigate the structure of polymers used in contact lenses. This technique allows the observation of the inner structure of polymers in the hydrated state. The ultrastructure, the polymer network underlying the outer surface of siloxane-hydrogels by cryoSEM microscopy, have never been reported before.
Journal of Applied Polymer Science, 1999
To test the validity of the method of stacked hydrogel contact lenses to obtain the oxygen permea... more To test the validity of the method of stacked hydrogel contact lenses to obtain the oxygen permeability and transmissibility coefficients of the lenses, the coefficients of one low hydration (38% water) and two high hydration (55 and 58% water) hydrogel contact lenses stacked one to five on an oxygen electrode were determined. From the oxygen diffusion through the lenses, the current intensity in the stationary state was determined, and from this the "instrument" the oxygen transmissibility was obtained. The permeability coefficients of the lenses, corrected for edge effects, were obtained from the slope of the plot of the reciprocal of the transmissibility coefficients versus the lens thicknesses. The oxygen permeability and transmissibility coefficients of the lenses obtained neglected the boundary layers resistance between the stacked lenses and, therefore, these are not the "true" coefficients. This article compares the "apparent" oxygen permeability coefficients of the hydrogel contact lenses, obtained by others, with the "true" oxygen permeability coefficients obtained with a corrected equation that takes into account the boundary layers between the stacked lenses.
Journal of Biomedical Materials Research, 2002
The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevi... more The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevisiontrade mark (balafilcon A) and Focus(R)Night&amp;amp;amp;amp;amp;amp;amp;amp;Daytrade mark (lotrafilcon A), were investigated. Standard hydrogel lenses of low (Seequence(R)), medium (Acuvue(R)), and high water content (Precision UV(R)) were used as controls. All the lenses were dehydrated in a series of ethanol solutions of increased concentration, critical-point dried in CO(2), and sputter coated with gold/palladium before they were examined by scanning electron microscopy. Of all lenses examined, only the balafilcon lenses presented, in addition to the polymer network porosity characteristic of all hydrogels, a macroporous structure that was observed on the front and back surfaces, and in their bulk. The average diameter of the macropores appears to be much larger, from one to several orders of magnitude, than the network porosity of standard hydrogel lenses. The macropores might contribute to the gas and water permeability of these lenses, as well as to their mobility on the cornea.
Journal of the American Optometric Association, 1999
BACKGROUND In this study, we evaluated the pH value of nine artificial tears solutions in order t... more BACKGROUND In this study, we evaluated the pH value of nine artificial tears solutions in order to investigate whether their pH changed over time. These solutions are designed to have a pH value within the ocular comfort range and to come close to the physiological tears' pH. METHODS Fifteen bottles of each solution were randomly chosen from different production lots. Increments of 0.05 ml were taken daily from each bottle and measured daily, using a micropH 2002 Crison pH-meter over a period of 60 days. RESULTS The values obtained fall within the ocular comfort range. Also, we obtained nonstatistically significant variations over time for each solution (p > 0.01). The results revealed differences between solutions, some solutions coming close to the tear's pH and others being slightly more acidic or alkaline. CONCLUSIONS We may assume that all the solutions evaluated will not affect either the ocular physiology or the contact lens wear. The practitioners should know the ...
Archivos de la Sociedad Española de Oftalmología
confirmados de COVID-19. Deberán ser adaptadas a las circunstancias y disponibilidad de equipos d... more confirmados de COVID-19. Deberán ser adaptadas a las circunstancias y disponibilidad de equipos de protección individual en cada uno de los centros y Comunidades Autónomas, debiendo ser actualizadas en función de las fases de la pandemia y de las medidas que adopte el Gobierno de la nación. Conclusiones: Durante la pandemia COVID-19, la atención a los potenciales riesgos de salud para la población ocasionados por el coronavirus deberá prevalecer sobre la posible progresión de enfermedades oculares comunes. Tanto médicos oftalmólogos como restantes profesionales de la salud ocular deberán asumir una posible progresión de dichas enfermedades ante la imposibilidad de un seguimiento adecuado de los pacientes.
Archivos de la Sociedad Española de Oftalmología (English Edition)
Objective: Minimize exposure to the SARS-CoV-2, reduce the chances of cross-transmission between ... more Objective: Minimize exposure to the SARS-CoV-2, reduce the chances of cross-transmission between patients and healthcare personnel, and prevent the development of postoperative complications from the management of patients with eye diseases during the 2019 coronavirus disease pandemic (COVID-19). Methods: COVID-19 literature review and consensus establishment between different Spanish ophthalmology societies in order to provide guidelines and recommendations of maximum resources primarily conditioned by the state of alert, confinement and social distancing that occurs in Spain since March 16, 2020. Results: The recommendations will promote the adoption of action and protection measures for eye care in outpatient clinics, surgical areas and hospitalization, for unconfirmed (asymptomatic and symptomatic) and confirmed COVID-19 patients. Measures must be adapted to the circumstances and availability of personal protective equipment in each of the centers
espanolObjetivo: Estudio de la transmisibilidad a los gases de lentes de contacto hidrofilas (LCH... more espanolObjetivo: Estudio de la transmisibilidad a los gases de lentes de contacto hidrofilas (LCH) multifocales disponibles en el mercado. Material y metodos: Con sonda polarografica acoplada a un permeometro se tomaron cinco medidas de transmisibilidad, en cinco LCH de 38%, 49%, 55%, 58% Y 73% de hidratacion. Resultados: Se encontraron diferencias cuali-y cuantitativas en el flujo de O₂ a traves de los diferentes materiales, siendo significativas las diferencias entre LCH de hidratacion superior al 50% y LCH de hidratacion inferior. Hubo tendencia de las lentes mas positivas hacia una menor transmisibilidad a los gases. No hubo diferencias significativas en el flujo de gases en relacion con el valor de la adicion, aunque paradojicamente las lentes con mayor adicion tendian a un mayor flujo de O₂. Conclusion: Las LCH de hidratacion media y alta poseen mayor transmisibilidad al Conclusion: Las LCH de hidratacion media y alta poseen mayor transmisibilidad al O₂, lo que es importante en la compensacion multifocal de hipermetropes. Al contrario de lo que sucede con el valor esferico, la adicion parece influir poco en la transmisibilidad, aunque esto varia segun el diseno. EnglishPurpose: Study of transmissibility to gases of on-the-counter multifocal hydrophilic contact lenses (LCH). Material and methods: With a polarographic probe coupled to a permeometer, 5 measures of transmissibility were taken on five LCH of 38%,49%, 55%, 58% and 73% hydration level. Results: Differences in O₂ flow quality and quantity were found through the different materials, being significant the differences between LCH with hydration higher than 50% and LCH of lower hydration. There was a tendency of more positive lenses towards less transmissibility to gases. Not significant differences were found on gas flux in relation to the addition value, although paradoxically, lenses with higher addition values had more oxygen flow. Conclusion: Medium and high water content LCH show more transmissibility to O₂, which is important ton the multifocal compensation of hyperopes. To the contrary of what happens with spherical value, addition seems to influence little on transmissibility, although this varies with the contact lens design.
espanolSe ha medido el contenido de agua de diferentes tipos de lentes hidrofilicas (LCH) utiliza... more espanolSe ha medido el contenido de agua de diferentes tipos de lentes hidrofilicas (LCH) utilizando tres refractometros manuales. El refractometro Atago N-2E es el que permite medir mayor numero de lentes con hidratacion entre 38% y 72%. Para lentes de alta hidratacion (>70%) y de baja hidratacion ( Se obtuvo una alta correlacion entre los valores referidos por el fabricante y los medidos por un observador con experiencia para las LCH convencionales (r²=0,966; p La refractometria manual permite realizar medidas precisas del contenido de agua de las LCH. Es necesario diferenciar claramente entre los materiales de hidrogel de silicona y los materiales de hidrogel convencionales cuando se pretenden medir cambios en el contenido de agua de las diferentes lentes como consecuencia de la utilizacion o para evaluar la capacidad de una LCH para hidratarse con farmacos para su utilizacion terapeutica, puesto que la refractometria manual sobreestima significativamente los valores reales de hidratacion para las LCHS. EnglishIn the present work, the water content of different hydrophilic contact lenses with three different hand-held refractometers has been measured. Atago N2-E allows to measure lenses in the range 32% to 72% water content. Lenses with high water content soft contact lenses (>70%) and low hydration ( A high correlation was found between the values quoted by the manufacturer and those measured by an experienced observer for conventional hydrogel lenses (r²=0.966; p As expected, there was not differences in hydration between positive and negative lenses of the same material (p=0.994), showing an excellent repeatability of the technique measuring different samples of the same material. Investigator’s experience with the technique demonstrated not to affect the variability of the measurements. Hand-held refractometry allows the precise estimation of the water content in hydrophilic soft contact lenses, as confirmed by previous investigations. It’s necessary to differentiate between conventional hydrogel materials and siloxane-hydrogels, as manual refractometry significantly overestimates the hydration ability of materials containing siloxane moieties
espanolObjetivo: Valorar en que medida la seleccion del material de la lente de contacto hidrofil... more espanolObjetivo: Valorar en que medida la seleccion del material de la lente de contacto hidrofila (LCH) y de la lente rigida permeable al gas (LCRPG) influyen en la consecucion del adecuado respeto fisiologico de los sistemas piggyback. Material y metodos: Seis LCH, con permeabilidad entre 8, 5 y 140 barrer, se combinaron con una lente de PMMA impermeable al gas y con tres lentes rigidas permeables al gas (24-189 barrer). Con una sonda polarografica acoplada a un permeometro se realizaron medidas de transmisibilidad, registrandose cinco medidas para cada sistema piggyback. Resultados: La lente de PMMA mostro la permeabilidad mas baja. Todas las demas combinaciones demostraron tener un efecto significativo en la permeabilidad al gas del sistema piggyback. Conclusion: Las lentes de PMMA no son adecuadas para sistemas piggyback. Para la compensacion de irregularidades corneales, por queratocono o queratoplastia con riesgo de neovascularizacion corneal, unicamente debe usarse la combinacion de LCH y LCRPG de alta permeabilidad. EnglishPurpose: Evaluate how selecting the material of a hydrophilic contact lens (HCL) and rigid gas permeable contact lens (RGP) influence the achievement of the appropriate physiological respect of the piggy-back systems. Material and methods: Six HCL, with premeabilities among 8.5 and 140 barrer, were combined with a PMMA contact lens impermeable to gas (24-189 barrer). With a polarographic probe coupled to a permeometer, transmissibility measures were obtained registering five measures for each piggyback system. Results: The PMMA lens showed the lowest permeability. All the remaining combinations showed a significant effect on the permeability to gas of the piggyback system. Conclusion: PMMA lenses are not adequate for piggyback systems. For the compensation of corneal irregularities, keratoconus or keratoplasty with risk of corneal neovascularization, only combinations of HCL and high permeability RGP should be used.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2009
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2007
To investigate the in vitro dehydration process of conventional hydrogel and silicone-hydrogel co... more To investigate the in vitro dehydration process of conventional hydrogel and silicone-hydrogel contact lens materials. Eight conventional hydrogel and five silicone-hydrogel contact lenses were dehydrated under controlled environmental conditions on an analytical balance. Data were taken at 1-min intervals and dehydration curves of cumulative dehydration (CD), valid dehydration (VD), and dehydration rate (DR) were obtained. Several quantitative descriptors of the dehydration process were obtained by further processing of the information. Duration of phase I (r(2) = 0.921), CD at end of phase I (r(2) = 0.971), time to achieve a DR of -1%/min (r(2) = 0.946) were strongly correlated with equilibrium water content (EWC) of the materials. For each individual sample, the VD at different time intervals can be accurately determined using a 2nd order regression equation (r(2) &amp;amp;gt; 0.99 for all samples). The first 5 min of the dehydration process show a relatively uniform average CD of about ...
Journal Français d'Ophtalmologie, 2005
JOURNAL-AMERICAN …, 1999
In this study, we evaluated the pH value of nine artificial tears solutions in order to investiga... more In this study, we evaluated the pH value of nine artificial tears solutions in order to investigate whether their pH changed over time. These solutions are designed to have a pH value within the ocular comfort range and to come close to the physiological tears' pH. Fifteen bottles of each solution were randomly chosen from different production lots. Increments of 0.05 ml were taken daily from each bottle and measured daily, using a micropH 2002 Crison pH-meter over a period of 60 days. The values obtained fall within the ocular comfort range. Also, we obtained nonstatistically significant variations over time for each solution (p > 0.01). The results revealed differences between solutions, some solutions coming close to the tear's pH and others being slightly more acidic or alkaline. We may assume that all the solutions evaluated will not affect either the ocular physiology or the contact lens wear. The practitioners should know the properties of the solutions, thus selecting the adequate solution for each type of patient.
Contact Lens and Anterior Eye, 1998
The pH of nine different brands of multipurpose contact lens solutions available in Spain was det... more The pH of nine different brands of multipurpose contact lens solutions available in Spain was determined over a period of 32 days after opening the bottles. Five bottles of nine solutions were used, each of which was buffered and obtained from different manufacturers. The pH measurements were taken using a micropH 2002 Crison pH-meter (accuracy + O. 001 pH units). Each solution was measured three times daily over the test period using lO-ml samples taken from the same container. Fluctuations in pH over time were observed but these were within the range of ocular comfort. The average pH of all the solutions tested proved to be between 6.99 and 7.56.
Biomaterials, 2004
The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemi... more The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemical procedures, is 5-10 times larger than that of conventional hydrogels. A method is described that allows the estimation of the oxygen tension at the lens-cornea interface for closed-and open-eyelids situations by combining the IOT of the hydrogels and corneal parameters such as corneal thickness, corneal permeability and oxygen flux across the cornea. From these results the biological oxygen apparent transmissibility (BOAT) is obtained, an important parameter which an multiplication with the pressure of oxygen on the external part of the lens gives the oxygen flux onto the cornea. Contact lenses with oxygen transmissibility higher than 100Dk/t units [1Dk/t unit=10 À9 [cm 3 O 2 (STp) cm À2 s À1 (mm Hg) À1 ] posses a large oxygen tension at the lens-cornea interface that substantially reduces the oxygen flux onto the cornea. Lenses whose oxygen transmissibility is lower than 50Dk/t units allow a rather small oxygen flux onto the cornea under closed eyelids condition that prevent their use for extended wear.