Effects of intraocular scatter on near peripheral vision.

Both cataracts and age-related macular degeneration (AMD) may occur with aging and are often developed simultaneously. We performed a study to better characterize the impact of induced scatter on the quality of vision in the near periphery, a region where individuals with AMD typically maintain their functional vision. We used an optical instrument as a cataract simulator based on projecting at the eye's pupil plane phase masks with controlled spatial properties generated with a spatial light modulator. The phase wavefronts were designed to accurately replicate the angular distribution of light intensity in the retina found in cataractous eyes with different severities. The induced amount of scatter ranged from values of straylight (S) from 10 to 85 degree2/sr, which corresponds from normal aging eye to advanced cataract stages. Mesopic visual acuity (VA) and contrast sensitivity (CS) at 3 cycles per degree were measured at the fovea and two retinal eccentricities (5 and 10 degrees in nasal visual field). We observed a consistent linear decline in VA (expressed in LogMAR) as the amount of induced scatter (quantified by the straylight parameter S) increased, both at the fovea and in the periphery. The effect of induced scattering on mesopic VA and CS at the fovea and the near periphery was evaluated. We found a relatively lower impact of scatter in the near periphery. This may explain the modest improvement in vision often found after cataract surgery in patients with AMD.

Using reflectometry to minimize the dependence of fluorescence intensity on optical absorption and scattering.

The total diffuse reflectance RT and the effective attenuation coefficient µeff of an optically diffuse medium map uniquely onto its absorption and reduced scattering coefficients. Using this premise, we developed a methodology where RT and the slope of the logarithmic spatially resolved reflectance, a quantity related to µeff, are the inputs of a look-up table to correct the dependence of fluorescent signals on the media's optical properties. This methodology does not require an estimation of the medium's optical property, avoiding elaborate simulations and their errors to offer accurate and fast corrections. The experimental demonstration of our method yielded a mean relative error in fluorophore concentrations of less than 4% over a wide range of optical property variations. We discuss how the method developed can be employed to improve image fidelity and fluorochrome quantification in fluorescence molecular imaging clinical applications.

Intraocular scatter compensation with spatial light amplitude modulation for improved vision in simulated cataractous eyes.

Cataract is one of the common causes of visual impairment due to opacification of the crystalline lens. Increased intraocular scattering affects the vision of cataract patients by reducing the quality of the retinal image. In this study, an amplitude modulation-based scatter compensation (AM-SC) method is developed to minimize the impact of straylight on the retinal image. The performance of the AM-SC method was quantified by numerical simulations of point spread function and retinal images in the presence of different amounts of straylight. The approach was also experimentally realized in a single-pass system with a digital micro-mirror device used as a spatial amplitude modulator. We showed that the AM-SC method allows to enhance contrast sensitivity in the human eyes in vivo with induced scattering.

Light scattering in intraocular lenses explanted 15 to 40 years after surgery.

The optical quality of intraocular lenses (IOLs) of different materials that have been implanted from 16 to 44 years in human eyes was studied. The IOLs were explanted due to other causes than loss of transparency. The scattered light from the IOLs was assessed in two angular regimes by using dark field images (for wide angles) and the optical integration method (for narrower angles). No evident differences were found in the scattering intensities processed from the dark images. The explanted lenses presented slightly increased amounts of straylight between 1 and 5.1° when compared to a reference new unused lens.

Phase-only modulation with two vertical aligned liquid crystal devices.

Spatial Light Modulators (SLMs) are widely used in several fields of optics such as adaptive optics. SLMs based on Liquid Crystal (LC) devices allow a dynamic and easy representation of two-dimensional phase maps. A drawback of these devices is their elevated cost, preventing a massive use of the technology. We present a more affordable approach based on the serial arrangement of vertical aligned LC devices, with characteristics of phase modulation similar to a widely used parallel aligned LC device. We discuss the peculiarities of the approach, the performance and some potential areas of applications.

Straylight in Different Types of Intraocular Lenses.

Purpose: To show the importance of measuring the angular distribution of straylight as an in vitro test for intraocular lenses (IOLs). Methods: The optical integration method was implemented to measure the point spread function, up to 5.1°, of IOLs immersed in a wet cell. The straylight parameter was calculated as the product of the point spread function by the squared angle. The effect of the scattered light is shown in extended images of a target surrounded by headlamps as glare sources. Three different IOLs were tested: (1) AcrySof IQ SN60WF, monofocal, (2) AcrySof IQ PanOptix, trifocal, and (3) Tecnis Symfony ZRX00, bifocal with extended depth of focus. Measurements were compared to previously reported clinical studies where the same IOL models were implanted. Results: The mean amount of scattered light, between 1.0° and 5.1°, generated by each IOLs were, in deg2sr-1 units: (1) 1.2, (2) 12.1, and (3) 33.4. Lens (3) present a high amount of straylight related to a halo of an approximate diameter of 2°. Conclusions: In vitro measurements of the angular distribution of the point spread function of different types of IOLs showed important aspects related to their manufacturing quality. These results are in line with previous clinical findings where glare sensitivity was tested in the same angular range. Translational Relevance: In vitro measurement of angular dependence of straylight in IOLs, regardless their design, provides a valuable feedback to improve their optical quality. The minimization of the amounts of straylight positively impacts the recurrence of photic phenomena.

Recommendations of the Colombian Consensus Committee for the Management of Traumatic Brain Injury in Prehospital, Emergency Department, Surgery, and Intensive Care (Beyond One Option for Treatment of Traumatic Brain Injury: A Stratified Protocol [BOOTStraP]).

Background Traumatic brain injury (TBI) is a global public health problem. In Colombia, it is estimated that 70% of deaths from violence and 90% of deaths from road traffic accidents are TBI related. In the year 2014, the Ministry of Health of Colombia funded the development of a clinical practice guideline (CPG) for the diagnosis and treatment of adult patients with severe TBI. A critical barrier to the widespread implementation was identified-that is, the lack of a specific protocol that spans various levels of resources and complexity across the four treatment phases. The objective of this article is to present the process and recommendations for the management of patients with TBI in various resource environments, across the treatment phases of prehospital care, emergency department (ED), surgery, and intensive care unit. Methods Using the Delphi methodology, a consensus of 20 experts in emergency medicine, neurosurgery, prehospital care, and intensive care nationwide developed recommendations based on 13 questions for the management of patients with TBI in Colombia. Discussion It is estimated that 80% of the global population live in developing economies where access to resources required for optimum treatment is limited. There is limitation for applications of CPGs recommendations in areas where there is low availability or absence of resources for integral care. Development of mixed methods consensus, including evidence review and expertise points of good clinical practices can fill gaps in application of CPGs. BOOTStraP (Beyond One Option for Treatment of Traumatic Brain Injury: A Stratified Protocol) is intended to be a practical handbook for care providers to use to treat TBI patients with whatever resources are available. Results Stratification of recommendations for interventions according to the availability of the resources on different stages of integral care is a proposed method for filling gaps in actual evidence, to organize a better strategy for interventions in different real-life scenarios. We develop 10 algorithms of management for building TBI protocols based on expert consensus to articulate treatment options in prehospital care, EDs, neurological surgery, and intensive care, independent of the level of availability of resources for care.

Light scattering in the human eye modelled as random phase perturbations.

Light scattering in the eye affects the quality of vision and its effect increases with aging and related pathologies, such as cataracts. Simulating methods were developed in order to reproduce the effects of this phenomenon. We introduce a statistical model of wavefront perturbations at the pupil plane of the eye that replicates the characteristic angular distribution of the light distribution over the retina. Our approach is based on the parameterization of the discrete cosine spectrum of the wavefront perturbation. The model performance was experimentally validated with a dedicated setup using a liquid crystal on silicon device as a spatial phase modulator. This instrument can be used for further visual experiments with controlled induction of light scattering.

Performance of a differential contrast sensitivity method to measure intraocular scattering.

Increased intraocular scatter degrades quality of vision, especially in the presence of glare sources. Standard tests, such as visual acuity, are not well suited to capture this condition. There are specific methods to measure intraocular scatter, but require dedicated instruments. In this work, we propose a method to estimate the amount of scatter by combining to sequential measurements of the contrast sensitivity function for two conditions, with and without a glare source. We applied the approach in a group of young subjects with no know ocular pathology fitted with photographic diffusing filters. The straylight estimates were compared with those provided by two alternative techniques, one based on the compensation comparison method and the other the optical integration. The results obtained with the three approaches were in a good agreement, demonstrating the feasibility of the proposed method.

Through-focus response of multifocal intraocular lenses evaluated with a spatial light modulator.

A new testing technique based on the use of a liquid crystal spatial light modulator (SLM) is proposed to analyze the optical quality of multifocal intraocular lenses (MIOLs). Different vergences and decentrations of the incident beam can be programmed onto the SLM in order to record the point spread function (PSF) for different object positions. From these axial PSFs, the through-focus modulation transfer function is computed. Because there are no moving parts in the experimental setup, this method is fast and versatile to assess MIOLs. Experimental results confirm the potential of the proposed method.

Experiencia multicéntrica colombiana durante tres años en el cierre percutáneo de la comunicación interventricular con diferentes dispositivos oclusores: propuesta para la simplicación de la técnica en pacientes seleccionados / Colombian multicentric experience during three years for percutaneous closure of interventricular septal defect with different occluder devices: proposal for technique simplification in selected patients

Objetivos: se describe la experiencia del cierre endovascular de comunicación interventricular realizada durante tres años en diferentes centros de cardiología intervencionista, y se destaca el resultado en un grupo de pacientes seleccionados en quienes dicho procedimiento se efectuó mediante el uso de un dispositivo de última generación diseñado para el cierre de ductus arterioso. Pacientes: entre junio de 2006 hasta octubre de 2009 se sometió un total de 34 pacientes a la técnica de oclusión de comunicación interventricular por vía endovascular. La indicación del procedimiento incluyó sobrecarga de volumen, sobrecarga de presión y volumen, falla cardiaca crónica, prolapso de válvula aórtica con insuficiencia y lesión traumática. La edad promedio fue de 12,9 años y el peso fue de 36 kilos. Se evidenció un predominio del sexo masculino (53 porciento. El promedio de cálculo de flujos demostró Qp/Qs de 1,71 a 1 y el de resistencias vasculares pulmonares fue 1,18 U Wood/m2. Materiales y Métodos: el dispositivo PM VSD Occluder se implantó con la técnica clásica (62,5 porciento) mientras que el dispositivo Duct Occluder II (28,1 porciento) se utilizó con la técnica simplificada propuesta. Se usó anestesia general en 98 porciento de los casos, 60 porciento fueron guiados con fluoroscopia y ecocardiografía transesofágica y 40 porciento con transtorácica. Resultados: el tamaño del defecto varió entre 4 y 12 mm. El 91 porciento de los pacientes tenía un defecto septal aislado. La mediana del tiempo quirúrgico se cuantificó en 56 minutos, siendo mayor en el grupo en el cual se utilizó la técnica clásica (85 min) en comparación con aquel grupo en el que se empleó la técnica simplificada con un promedio de 36 minutos...

Objectives: we describe the experience of the endovascular closure of interventricular communication performed for three years in different centers of interventional cardiology and highlight its result in a group of selected patients in whom such procedure was made by the use of a last generation device designed for the closure of ductus arteriosus. Methodology: between June 2006 and October 2009, a total of 34 patients underwent endovascular occlusion for interventricular septal defect. Indication of this procedure included volume overload, pressure and volume overload, chronic congestive heart failure, aortic valve prolapse with insufficiency and traumatic injury. Mean age was 12,9 years old and mean weight was 36 kg. A prevalence in male gender (53 porciento) was evidenced. Main blood flow calculation showed Qp / Qs of 1.71 to 1 and the pulmonary vascular resistance was 1.18 U Wood/m2. Materials and methods: PM VSD occluder device was implanted with the classic technique (62,5 porciento) while the Duct Occluder II (28,1 porciento) was used with the proposed simplified technique. General anesthesia was used in 98 porciento cases; 60 porciento were guided by fluoroscopy and transesophageal echocardiography and 40 porciento with transthoracic echocardiography. Results: size of the defect varied from 4 to 12 mm. 91 porciento of patients had an isolated septal defect. Mean surgical time was 56 min, being longer in the group in which the classic technique was used (85 min) compared with the group in which the technique used was the simplified one, with a mean duration of 36 min. Mean hospital stay was estimated in 36 hours. Follow up: complete closure was documented in 100 porciento of patients at 30 days. There were three adverse events due to minor complications related to transient rhythm disturbances...