Photochromic dynamics of ophthalmic lenses

We describe and characterize a straightforward test setup for characterizing temporal and spectral dynamics of photochromic spectacle materials. Three measurement examples of contemporary silicate and organic photochromic spectacles are provided. The setup showed a good absolute accuracy of ≤5% of the luminous transmittance (τ(v)) and repeatability of better than 3%. The samples showed different fading times. The sample with the highest dynamic range was the slowest and showed a noticeable change in the transmission spectra during deactivation. The silicate had the lowest dynamic range but also the most homogeneous transmission spectra throughout activation and deactivation. The proposed test device provided accurate results for spectral and temporal dynamics of photochromic materials under realistic conditions.     

五行学说与框架眼镜设计

目的研究传统文化中五行学说对框架眼镜设计的影响。方法通过了解五行学说,分析命理五行及其与框架眼镜之间的关系,将框架眼镜设计与五行学说相结合,研究五行学说在框架眼镜设计中造型、色彩和材料3个方面的设计要求。结论旨在从传统文化五行学说的哲学理念中找寻适合于框架眼镜设计的形式与方法。     

Effects on driving performance of visual field defects: a driving simulator study

To elucidate the possible traffic safety risks induced by visual field defects, a method was developed based on a driving simulator. The capacity to detect stimuli of different sizes appearing in 24 different positions on the screen in front of the driver was measured. Two groups of normal subjects and a number of subjects with different visual field defects were studied. In the groups of normals, the median reaction times were fairly homogenous. There was a slight difference between central and peripheral stimuli, which was somewhat larger for the older subjects. Among the subjects with field defects, the individual variations were very dominant. Very few of these showed a capacity to compensate for their deficiency. In order to gain insight into possible compensatory mechanisms of these persons, eye movement recordings were made. The results indicate that the visual search pattern may be of importance in this respect. Some comparisons with respect to detection capacity were also made with one-eyed subjects and with optically generated field restrictions (spectacles and spectacle frames).     

Mediated-reality magnification for macular degeneration rehabilitation

Age-related macular degeneration (AMD) is a gradually progressive eye condition, which is one of the leading causes of blindness and low vision in the Western world. Prevailing optical visual aids compensate part of the lost visual function, but omitting helpful complementary information. This paper proposes an efficient magnification technique, which can be implemented on a head-mounted display, for improving vision of patients with AMD, by preserving global information of the scene. Performance of the magnification approach is evaluated by simulating central vision loss in normally sighted subjects. Visual perception was measured as a function of text reading speed and map route following speed. Statistical analysis of experimental results suggests that our magnification method improves reading speed 1.2 times and spatial orientation to find routes on a map 1.5 times compared to a conventional magnification approach, being capable to enhance peripheral vision of AMD subjects along with their life quality.     

浅析GB 13511.1-2011配装眼镜 第1部分 单光和多焦点部分条款及验配眼镜产品生产许可证企业实地核查要点

本文主要论述GB 13511.1-2011国家标准修订情况,新旧两版本的差异,并对验配眼镜生产许可证实地核查提出一些建议。     

Contrast sensitivity with presbyopic contact lenses

The purpose of the work was to assess the contrast sensitivity function of individuals wearing gas permeable (GP) multifocal contact lenses, soft bifocal contact lenses, and GP monovision lenses. Twenty-six females and six males between the ages of 42 and 65 participated in this study. The study included subjects wearing monovision (N?=?8), the Acuvue Bifocal (Johnson & Johnson) (N?=?8), Essential GP Multifocal (Blanchard) lenses (N?=?8) and progressive addition spectacle lenses (PAL) (N?=?8), with PAL wearers forming the control group. Measurements of binocular contrast sensitivity were obtained using the VISTECH 6500 system. Thresholds for each spatial frequency were fit to the equation CS(k)?=?ak?exp(?bk) [1?+?c exp(bk)]^?1/2, to describe the human contrast sensitivity function. The area under the contrast sensitivity function (CSF) curve was calculated for all four groups and compared. An index of performance was obtained, which was defined as the ratio of CSF with the contact lens correction to the CSF with spectacles. Of the contact lens wearing groups, GP multifocal contact lens wearers had the highest contrast sensitivity at all the spatial frequencies. Soft bifocal contact lens wearers exhibited higher contrast sensitivity than monovision wearers at all spatial frequencies. Subjects wearing GP multifocals had the largest area under the CSF; followed by those wearing soft bifocals, with monovision wearers having the smallest area. GP multifocals have the best visual function at 0.98, soft bifocals have an index of 0.65 and monovision has an index of 0.59. This study quantifies the visual performance of the three lens systems by measuring the area under the CSF curve. In addition, it provides indices of visual function with the contact lenses that will be helpful for analyses and comparisons in future studies.     

Hypoxia, color vision deficiencies, and blood oxygen saturation

Chromatic thresholds were measured using the Cambridge Colour Test (CCT), the Colour Assessment and Diagnosis (CAD) test, and the Cone Specific Contrast Test (CSCT) at ground and 3780 m (12,400 ft) for subjects with normal color vision and red-green color vision defects. The CAD revealed a small (~10%) increase in the red-green thresholds for the trichromatic subjects and a similar increase in the blue-yellow thresholds for the dichromats. The other two color vision tests did not reveal any significant change in chromatic thresholds. The CAD results for the trichromats were consistent with a rotation of the discrimination ellipse counterclockwise with little change in the elliptical area. This alteration in the color discrimination ellipse can occur when retinal illumination is lowered.     

Image Quality Considerations in ESO Telescope Projects

The European Southern Observatory (ESO) has immediate plans for the construction of a ‘New Technology Telescope’ (NTT) of about 3–3·5 m aperture and is studying a project for a ‘Very Large Telescope’ (VLT) of 16m equivalent aperture. Some characteristics of these telescopes are discussed, particularly the possibilities of greatly improved optical performance through active optics, closed-loop control. In this connection the problem is approached from the physical origins of the stable or quasi-stable optical aberration function which, apart from high frequency seeing, sets the limits of optical quality of telescopes in practice.     

Productivity and impact of large optical telescopes

An attempt is made to provide quantitative measures of the amount of data gathered at large optical telescopes throughout the world and the impact these data have on astronomical research. The data base comprises 1163 papers reporting data from 39 telescopes, published between January 1990 and June 1991, and 4052 citations to them in 1993. Productivity measured in papers per square meter of telescope mirror varies by a factor of six, and impact measured in citations per paper varies by a factor of more than 10. Predictably, high productivity and high impact are associated with telescopes located at good sites and fully supported for many years by organizations with large budgets. Low productivity and low impact are associated with less favorable locations, short periods of operation, and financial stringency. In addition, the most productive telescopes seem to be ones whose users include astronomers from a wide range of geographical locations.January to June.July to December     

Content uniformity acceptance limit for a validation batch—suppositories,transdermal systems,and inhalations

Background: The USP test for ‘Uniformity of Dosage Units’ specified by USP Chapter <905> is required of every drug product sold in the United States. Dosage-unit uniformity is determined either by weight variation or by assay of individual units. The USP acceptance criteria for content uniformity states that the relative standard deviation (RSD) of a sample of 30 units should not exceed 7.8%. Purpose: This article provides a methodology for deriving an upper acceptance limit on the RSD of dosage units from a validation batch of suppositories, transdermal systems, or inhalations such that future batches will have a 95% chance of passing the USP content uniformity RSD acceptance criterion (the RSD of 30 dosage units does not exceed 7.8%).     

Equal-curvature grazing-incidence x-ray telescopes

We introduce a new type of x-ray telescope design, an equal-curvature telescope. We simply add a second-order axial sag to the base grazing-incidence cone-cone telescope. The radius of curvature of the sag terms is the same on the primary surface and on the secondary surface. The design is optimized such that the on-axis image spot at the focal plane is minimized. The on-axis rms spot diameter of two telescopes that we studied is less than 0.2 arc sec. The off-axis performance is comparable with that of equivalent Wolter type 1 telescopes.     

The x-ray astronomy experiment

One of the scientific experiments onboardAryabhata was designed to detect and measure celestial x-rays in the energy range 2.5–155.0 keV. The payload systems comprising proportional counter and scintillation counter, telescopes were intended for observations in the pointed and scan modes respectively for investigating the emission properties of celestial x-ray sources. The paper presents the details of these telescopes, their inflight performance as well as the nature of the data obtained during the first few orbits.     

Exploring the antioxidant potentiality of two food by-products into a topical cream: stability,in vitro and in vivo evaluation

Abstract

Context: Coffee silverskin (CS), a food by-product of the coffee roasting industry, has been studied as an active ingredient for skin care products due to its high potential of antioxidant activity and low cytotoxicity. Another food waste used as ingredient with promising characteristics is obtained from Medicago sativa (MS), which antioxidants and isoflavones content is high.

Objective: The aim of this study is to evaluate and characterize a new body formulation containing two food by-products extracts.

Materials and methods: Different parameters (such as pH, rheological behavior, color, antioxidant content and microbiological analysis) of a body cream formulation containing by-products (CSMS) and a formulation without extracts (F) were evaluated under a stability study during 180 days at different temperatures. Moreover, the in vitro cell toxicity and the in vivo skin safety and protective effects were also assessed.

Results: Formulation showed stable physical properties and antioxidant activity during 180 days of storage. In vitro toxicity was screened in two skin cell lines (fibroblasts and keratinocytes) and any toxicity was reported. The in vivo test carried out showed that, with respect to irritant effects, CSMS formulation can be regarded as safe for topical application and the skin hydratation improved after 30 days of its use. Also, considering the consumer acceptance, more than 90% of volunteers classified it as very pleasant.

Conclusions: CSMS formulation is stable and safe for topical use as no adverse and/or side effects were observed during the application period of testing, improving skin protective properties.     

Fracture toughness determination and microstructure investigation of a B4C–NanoTiB2 composite with various volume percent of Fe and Ni additives

Boron carbide (B₄C) has wide application in manufacturing of abrasives and cutting tools, due to its unique features such as high hardness, good wear resistance, low specific weight and chemical stability. An additive reinforcing phase and sintering aids are used to improve its sinterability. In the present paper, a B₄C composite with 10 vol.% of titanium diboride nanoparticles (TiB₂) and a 0, 1.5 and 2.5 vol.% iron or nickel metallic additive, respectively, was mixed in an isopropanol environment containing tungsten carbide pellets. After drying, the obtained mixture was formed by cold pressing. The obtained parts were sintered at 2400 °C. The effect of adding metallic sintering aids on the mechanical properties and microstructure of the composite was investigated and fracture toughness values were evaluated by indentation test method. Addition of Fe and Ni improved values for density, hardness, Young’s modulus and fracture toughness, with Ni addition increasing the values considerably. Scanning electron microscope (SEM) images of the microstructure of the specimens showed the arrangement posture of the additives and confirmed the results obtained. Additionally, the FeB and Ni₃B blades formation were observed from the images.     

Bulk magnetic properties of Co-Zn ferrites prepared by the co-precipitation method

The alternating current (a.c.) susceptibility versus temperature and magnetization measurements are reported for the disordered spinel ferrite system Zn _x Co_1-x Fe₂ O₄ prepared by a wet chemical method before and after high temperature annealing. The low field a.c. susceptibility measurements indicate that the low temperature synthesis of wet prepared Co-Zn ferrites aids the formation of spin-clusters and thereby increases the magnetic inhomogeneity. The X-ray analysis shows that the samples are single phase spinels and the variation of lattice constant with zinc concentration deviates from Vegard's law [1]. The high temperature annealing changes the wet prepared ferrites into the ordered magnetic structure of the ceramic ferrites.     

Calculation of optical imbalances in ophthalmic lenses using a new algorithm based on the local dioptric power matrix formalism.

We present a new algorithm to calculate the optical imbalances and differential prismatic effects that appear when two eyes look at an object through correcting eyeglasses. These are important magnitudes in ophthalmic optics because large amounts of them will disturb the binocular vision of the spectacle wearer. As a practical application of our algorithm, the distribution of optical imbalances and differential prismatic powers for a pair of progressive addition lenses has been calculated, and we obtain information about the effects of this kind of lens on the binocular vision of the wearer.     

The 3-D-3 Rangefinder and Depth of Field Indicator

A wander mark stereoscopic rangefinder using the normal eye separation as Its base length is described. It has two main controls: one carries a scale of ranges and could be coupled to the focusing mechanism of a camera lens; the other carries a scale af lens apertures and could be coupled to the stop setting mechanism of the lens. Three indicating marks appear In space at variable distances from the observer, to show the range and depth of field limits set by the controls. The optical system consists of an illuminated diapositlve, a collimating lens and three partially reflecting mirrors. It gives autamatic campensation for varying eye separations of different observers, is accurate and easy to use, even by spectacle wearers. The rangefinder affers advantages aver established methods of setting focus In both still and cine photography, particularly in low light and on moving subjects. Under these conditions the depth of field indication is a valuable asset.     

Adaptive optics for peripheral vision

Understanding peripheral optical errors and their impact on vision is important for various applications, e.g. research on myopia development and optical correction of patients with central visual field loss. In this study, we investigated whether correction of higher order aberrations with adaptive optics (AO) improve resolution beyond what is achieved with best peripheral refractive correction. A laboratory AO system was constructed for correcting peripheral aberrations. The peripheral low contrast grating resolution acuity in the 20° nasal visual field of the right eye was evaluated for 12 subjects using three types of correction: refractive correction of sphere and cylinder, static closed loop AO correction and continuous closed loop AO correction. Running AO in continuous closed loop improved acuity compared to refractive correction for most subjects (maximum benefit 0.15?logMAR). The visual improvement from aberration correction was highly correlated with the subject's initial amount of higher order aberrations (p?=?0.001, R ^2?=?0.72). There was, however, no acuity improvement from static AO correction. In conclusion, correction of peripheral higher order aberrations can improve low contrast resolution, provided refractive errors are corrected and the system runs in continuous closed loop.     

Functional performance of silicified microcrystalline cellulose versus microcrystalline cellulose: a case study

Background: During the development of a tablet dosage form of an investigational compound, R411, several aspects were identified as critical quality attributes that required optimization. The use of nonsolvent processing prevented the moisture-induced physical changes in the drug product but presented manufacturing challenges related to sticking during compression and slowdown in dissolution after storage at stress conditions. Aim: The aim of this study was to evaluate silicified microcrystalline cellulose (SMCC), microcrystalline cellulose (MCC), and physical mixture of MCC–colloidal silicon dioxide (MCC/CSD at 98:2 ratio) as extragranular compression aids to address the processing and dissolution stability issues of this formulation. Methods: The compactibility and stickiness upon compression over extended period of time as well as the dissolution of R411 formulations incorporating the aforementioned compression aids were investigated. In addition, the water sorption/desorption properties of these compression aids were determined. Results: All formulations showed comparable compactibility irrespective of the compression aid used. Nevertheless, MCC alone or in a physical mixture with CSD showed sticking of the lower punches, whereas SMCC resulted in clean punch surface during extended compression runs. Furthermore, the three compression aids were compared for their effect on dissolution stability after storage at stress conditions. The formulations containing SMCC provided superior dissolution stability over the other compression aids evaluated in the study. Conclusions: Novel functionalities of SMCC are presented in terms of sticking prevention while having the most beneficial effect on dissolution stability in R411 formulation.