Visual performance with tinted contact lenses

During extensive research of the several tinted contact lenses on the market, a lack of information was noted as to whether or not tinted contact lenses can effect visual acuity under conditions of varying contrast. With this in mind we conducted a study to determine the effect of tinted contact lenses on visual performance under high and low contrast conditions. Using twenty-four research subjects, high and low contrast visual acuities were documented in order to compare performance with tinted to clear contact lenses. Two tints were chosen, royal blue and evergreen, with each person serving as their own control by wearing a pair of clear lenses. Subjects accepted for the study were required to have small refractive errors, + 1.00 to -4.00 diopters with astigmatism less than 0.75 diopters. Acuities were measured using Bailey-Lovie LogMAR contrast acuity charts, and the data analyzed with paired t-tests. The data showed that visual acuity decreased by approximately 1/2 a Snellen line under high and low contrast conditions compared to the clear lens performance. These data suggest that visual performance deficits can occur when tinted lenses are prescribed for cosmetic purposes, particularly under conditions of varying contrast. This may have impact in situations ranging from safety in the workplace to performance in sports or fine visual motor tasks, and it is suggested that patients be informed of possible difficulties when wearing deeply tinted cosmetic lenses

Study of astronaut capabilities to perform extravehicular maintenance and assembly functions in weightless conditions

Analysis of astronaut capabilities to perform extravehicular maintenance and assembly functions under simulated weightlessnes

A New Classification System for the Actions of IRS Chemicals Traditionally Used For Malaria Control

Knowledge of how mosquitoes respond to insecticides is of paramount importance in understanding how an insecticide functions to prevent disease transmission. A suite of laboratory assays was used to quantitatively characterize mosquito responses to toxic, contact irritant, and non-contact spatial repellent actions of standard insecticides. Highly replicated tests of these compounds over a range of concentrations proved that all were toxic, some were contact irritants, and even fewer were non-contact repellents. Of many chemicals tested, three were selected for testing in experimental huts to confirm that chemical actions documented in laboratory tests are also expressed in the field. The laboratory tests showed the primary action of DDT is repellent, alphacypermethrin is irritant, and dieldrin is only toxic. These tests were followed with hut studies in Thailand against marked-released populations. DDT exhibited a highly protective level of repellency that kept mosquitoes outside of huts. Alphacypermethrin did not keep mosquitoes out, but its strong irritant action caused them to prematurely exit the treated house. Dieldrin was highly toxic but showed no irritant or repellent action. Based on the combination of laboratory and confirmatory field data, we propose a new paradigm for classifying chemicals used for vector control according to how the chemicals actually function to prevent disease transmission inside houses. The new classification scheme will characterize chemicals on the basis of spatial repellent, contact irritant and toxic actions

The Mists of Development: Fairtrade in Kenyan Tea Fields

Increasing numbers of consumers see themselves as ‘partners’ in poverty reduction, purchasing Fairtrade products to offset inequalities in the global economy and to ensure that producers in developing countries enjoy the same basic rights and freedoms as their Western counterparts. Yet the extent to which ethical consumption is restructuring commodity chains in a way that diminishes hierarchies between producers and consumers remains an open question. Drawing on a qualitative research project of ethical sourcing in African agriculture, this paper discusses the extent to which key tenets of the fair trade system—empowerment, transparency, equal exchange, and democratic participation—are realized among Fairtrade tea producers in Kenya. It suggests that while such ideals embrace the aspirations of sustainable development, their achievement remains distant from the experience of many producers, for whom ethical outcomes are shaped by an array of conflicting interests, both within and beyond the commodity chain