Susceptibility to pattern glare and the effect of spectral filters on rate of reading and visual search in stroke patients

The present thesis investigates pattern glare susceptibility following stroke and the immediate and prolonged impact of prescribing optimal spectral filters on reading speed, accuracy and visual search performance. Principal observations: A case report has shown that visual stress can occur following stroke. The use of spectral filters and precision tinted lenses proved to be a successful intervention in this case, although the parameters required modification following a further stroke episode. Stroke subjects demonstrate elevated levels of pattern glare compared to normative data values and a control group. Initial use of an optimal spectral filter in a stroke cohort increased reading speed by ~6% and almost halved error scores, findings not replicated in a control group. With the removal of migraine subjects reading speed increased by ~8% with an optimal filter and error scores almost halved. Prolonged use of an optimal spectral filter for stroke subjects, increased reading speed by >9% and error scores more than halved. When the same subjects switched to prolonged use of a grey filter, reading speed reduced by ~4% and error scores increased marginally. When a second group of stroke subjects used a grey filter first, reading speed decreased by ~3% but increased by ~3% with prolonged use of an optimal filter, with error scores almost halving; these findings persisted with migraine subjects excluded. Initial use of an optimal spectral filter improved visual search response time but not error scores in a stroke cohort with migraine subjects excluded. Neither prolonged use of an optimal nor grey filter improved response time or reduced error scores in a stroke group; these findings persisted with the exclusion of migraine subjects

The radio remnant of SN1993J: an instrumental explanation for the evolving complex structure

We present simulated images of Supernova 1993J at 8.4 GHz using Very Long Baseline Interferometry (VLBI) techniques. A spherically symmetric source model is convolved with realistic uv-plane distributions, together with standard imaging procedures, to assess the extent of instrumental effects on the recovered brightness distribution. In order to facilitate direct comparisons between the simulations and published VLBI images of SN1993J, the observed uv-coverage is determined from actual VLBI observations made in the years following its discovery. The underlying source model only exhibits radial variation in its density profile, with no azimuthal dependence and, even though this model is morphologically simple, the simulated VLBI observations qualitatively reproduce many of the azimuthal features of the reported VLBI observations, such as appearance and evolution of complex azimuthal structure and apparent rotation of the shell. We demonstrate that such features are inexorably coupled to the uv-plane sampling. The brightness contrast between the peaks and the surrounding shell material are not as prominent in the simulations (which of course assume no antenna- or baseline-based amplitude or phase errors, meaning no self-calibration procedures will have incorporated any such features in models). It is conclusive that incomplete uv-plane sampling has a drastic effect on the final images for observations of this nature. Difference imaging reveals residual emission up to the 8 sigma level. Extreme care should be taken when using interferometric observations to directly infer the structure of objects such as supernovae.Comment: 14 pages, 10 figures, 2 tables, accepted for publication in MNRA

Effect of peripheral defocus on axial eye growth and modulation of refractive error in hyperopes

Hyperopia is a known risk factor for the development of strabismus and amblyopia. In addition to visual consequences there is a growing body of evidence that uncorrected hyperopia may have a negative impact on educational attainment and visuocognitive and visuomotor skills. Currently, hyperopia receives much less attention from research than myopia even though the impact of moderate to high levels of hyperopia especially in one eye (anisohyperopia) can lead to amblyopia if not corrected fully at a young age. Hyperopia occurs as a consequence of insufficient ocular growth and a failure to emmetropise in childhood with the majority of hyperopic refractive errors resulting from an eye that is too short for its refractive power. In anisohyperopia it is unclear why one eye may remain hyperopic while the fellow eye grows towards an emmetropic state. Studies on animals have suggested that manipulating peripheral defocus through an optical means while simultaneously providing correct axial focus can either discourage or encourage axial eye growth to effectively treat myopia or hyperopia, respectively. Recent research has established that progression of myopia and axial eye growth can be significantly reduced in children and adolescents through the use of bifocal or multifocal contact lenses. These contact lenses while correcting the distance central myopia impose simultaneous myopic defocus. In recent years there has been a great deal of interest in delaying progression of myopia (short-sightedness) by slowing eye growth using a particular type of contact lens termed a centre-distance multifocal design. There have been encouraging results in this area to date. The proposed study here would explore the use of centre-near multifocal design contact lenses to encourage eye growth, thereby reducing hyperopia. There are three elements to the programme of research: 1. The natural progression of axial eye growth and refractive error will be measured in spectacle wearing hyperopic and anisohyperopic subjects aged between 5 and <19 years. In other words, the natural growth of the eye will be followed without intervention 2. As a paired eye control study anisohyperopes aged between 8 and <16 years will be fitted with a centre-near multifocal design contact lens in their more hyperopic eye and a single vision contact lens in the fellow eye if required. The progression of axial eye growth and refractive error will be measured and compared 3. Subjects aged between 8 and <16 years with similar levels of hyperopia in each eye will be fitted with centre-near multifocal design contact lenses in each eye. The progression of axial eye growth and refractive error will be measured and compared to subjects in the natural progression study. The objectives of the study are to: • Understand the natural progression of axial eye growth and refractive error in hyperopes and anisohyperopes • Establish if axial eye growth and refractive error can be modified using centre-near multifocal design contact lenses in hyperopes and anisohyperopes to improve visual outcome

The Effect of Peripheral Defocus on Axial Growth and Modulation of Refractive Error in Hyperopes

Despite the known visual and pathological implications of hyperopia, there has been inertia to address the modulation of refractive error in these individuals. Imposing relative peripheral hyperopic defocus using centre-near multifocal contact lenses accelerates axial growth in isohyperopic children. Axial growth and refractive error did not change during the 6 months prior to intervention in the intervention or control group. Axial growth across the 2-year period of intervention was 0.17 mm in the intervention group versus 0.06 mm in the control group. Refractive error change across the same period was -0.26 D in the intervention group and +0.01 D in the control group. Axial growth and refractive error during the final 6 months without intervention did not change in either group. The overall difference in axial growth between groups was significant whereas the change in refractive error was not. Imposing relative peripheral hyperopic defocus using centre-near multifocal contact lenses does not accelerate axial growth nor reduce refractive error in anisohyperopic children. In this paired eye study, axial growth and refractive error did not change during the 6 months prior to intervention in either eye. Axial growth across the 2-year period of intervention was 0.11 mm in the intervention eye versus 0.15 mm in the control eye. Refractive error change across the same period was -0.23 D in the intervention eye and -0.27 D in the fellow eye. Axial growth and refractive error during the final 6 months without intervention did not change in either group. The overall change in axial growth was greater in the control eye than the intervention eye, whereas the reduction in refractive error was comparable. Axial length measures are comparable and repeatable under pre- and post-cycloplegic conditions. Refractive error measures are comparable and repeatable at discrete time intervals after the instillation of a cycloplegic agent

Crédito de carbono como oportunidade de negócio

A falta de conhecimento aliada à busca pela sobrevivência e pelo poder causaram ao meio ambiente e principalmente ao clima, bruscas variações. A cada ano a preocupação com o futuro dos recursos naturais vem aumentando e cada vez mais tem se buscado preservá-los para o presente e para as futuras gerações. Os consumidores têm buscado cada vez mais produtos socialmente responsáveis. A emissão de gases do efeito estufa provinda das atividades pecuárias pode ser vista como uma oportunidade de negócio. A criação de bovinos e suínos pode se transformar em uma opção mais rentável do que se imagina. O que antes era desperdiçado e servia apenas para poluir, pode se transformar em reduções de custo e ingresso a um novo mercado em plena expansão, altamente promissor, o mercado de créditos de carbono. Para que isso aconteça é necessário desenvolver um planejamento estratégico, visando a implantação de uma gestão ambiental, tornando propriedades poluidoras em auto-sustentáveis, obtendo assim, um aumento da lucratividade. O empreendedorismo foi lançado na busca de transformar a criação de bovinos e suínos em regime de confinamento em atividades que visem o maior aproveitamento de seus dejetos, transformando-os em novos produtos que ajudem na batalha contra o aquecimento global. Pesquisa bibliográfica e observação foram os meios encontrados para o desenvolvimento desse trabalho. O objetivo foi alcançado

The effect of peripheral defocus on axial growth and modulation of refractive error in hyperopes

Purpose: To establish whether axial growth and refractive error can be modulated in hyperopic children by imposing relative peripheral hyperopic defocus using multifocal soft contact lenses. Methods: A prospective controlled study with hyperopic participants allocated to a control or test group. Control group participants were corrected with single vision spectacles and changes to axial length and refractive error were followed for 3 years. For the test group, axial growth and post-cycloplegic refractive error were observed with participants wearing single vision spectacles for the first 6 months of the trial and then corrected with centre-near multifocal soft contact lenses with a 2.00 D add for 2 years. The central ‘near’ portion of the contact lens corrected distance refractive error while the ‘distance’ portion imposed hyperopic defocus. Participants reverted to single vision spectacles for the final 6 months of the study. Results: Twenty-two participants, mean age 11.13 years (SD 1.72) (range 8.33-13.92), completed the trial. Axial length did not change during the first 6 months in either group (P = 1.000). Axial growth across the 2-year intervention period was 0.17 mm (SEM 0.04) (P < 0.0005) in the test group versus 0.06 mm (SEM 0.07) (P = 0.677) in the control group. Axial length was invariant during the final 6 months in either group (P = 1.000). Refractive error was stable during the first 6 months in both groups (P = 1.000). Refractive error change across the 2-year intervention period was -0.26 D (SEM 0.14) (P = 0.375) in the test group versus -0.01 D (SEM 0.09) (P = 1.000) in the control group. Neither the test (P=1.000) nor control (P=0.628) group demonstrated a change in refractive error during the final 6 months. Conclusions:  The rate of axial growth can be accelerated in children with hyperopia using centre-near multifocal soft contact lenses

Does rebound tonometry probe misalignment modify intraocular pressure measurements in human eyes?

Purpose. To examine the influence of positional misalignments on intraocular pressure (IOP) measurement with a rebound tonometer. Methods. Using the iCare rebound tonometer, IOP readings were taken from the right eye of 36 healthy subjects at the central corneal apex (CC) and compared to IOP measures using the Goldmann applanation tonometer (GAT). Using a bespoke rig, iCare IOP readings were also taken 2 mm laterally from CC, both nasally and temporally, along with angular deviations of 5 and 10 degrees, both nasally and temporally to the visual axis. Results. Mean IOP ± SD, as measured by GAT, was 14.7±2.5 mmHg versus iCare tonometer readings of 17.4±3.6 mmHg at CC, representing an iCare IOP overestimation of 2.7±2.8 mmHg (P<0.001), which increased at higher average IOPs. IOP at CC using the iCare tonometer was not significantly different to values at lateral displacements. IOP was marginally underestimated with angular deviation of the probe but only reaching significance at 10 degrees nasally. Conclusions. As shown previously, the iCare tonometer overestimates IOP compared to GAT. However, IOP measurement in normal, healthy subjects using the iCare rebound tonometer appears insensitive to misalignments. An IOP underestimation of <1 mmHg with the probe deviated 10 degrees nasally reached statistical but not clinical significance levels. © 2013 Ian G. Beasley et al

Dose-response relationship of ICS/fast-onset LABA as reliever therapy in asthma

The dose-response relationship of inhaled corticosteroid (ICS)/fast-onset long acting beta agonist (LABA) reliever therapy has not been formally addressed. The objective of this retrospective analysis is to ascertain from the available evidence whether ICS/fast-onset LABA administered as reliever therapy has a different dose-response relationship than maintenance fixed dose ICS/fast-onset LABA therapy in reducing risk of severe exacerbations