Strategies to regulate myopia progression with contact lenses: a review

Purpose: Higher myopic refractive errors are associated with serious ocular complications that can put visual function at risk. There is respective interest in slowing and if possible stopping myopia progression before it reaches a level associated with increased risk of secondary pathology. The purpose of this report was to review our understanding of the rationale(s) and success of contact lenses (CLs) used to reduce myopia progression. Methods: A review commenced by searching the PubMed database. The inclusion criteria stipulated publications of clinical trials evaluating the efficacy of CLs in regulating myopia progression based on the primary endpoint of changes in axial length measurements and published in peerreviewed journals. Other publications from conference proceedings or patents were exceptionally considered when no peer-review articles were available. Results: The mechanisms that presently support myopia regulation with CLs are based on the change of relative peripheral defocus and changing the foveal image quality signal to potentially interfere with the accommodative system. Ten clinical trials addressing myopia regulation with CLs were reviewed, including corneal refractive therapy (orthokeratology), peripheral gradient lenses, and bifocal (dual-focus) and multifocal lenses. Conclusions: CLs were reported to be well accepted, consistent, and safe methods to address myopia regulation in children. Corneal refractive therapy (orthokeratology) is so far the method with the largest demonstrated efficacy in myopia regulation across different ethnic groups. However, factors such as patient convenience, the degree of initial myopia, and non-CL treatments may also be considered. The combination of different strategies (i.e., central defocus, peripheral defocus, spectral filters, pharmaceutical delivery, and active lens-borne illumination) in a single device will present further testable hypotheses exploring how different mechanisms can reinforce or compete with each other to improve or reduce myopia regulation with CLs.

Som em frequência moderada: cartografia dos estudos de rádio em Portugal

[Excerto] Na academia como no mercado mediático, a rádio goza de um estatuto relativamente modesto. Sem os exibicionismos próprios dos meios visuais, o meio radiofónico define-se por uma presença ao mesmo tempo popular e discreta, simples e elegante, na vida quotidiana. Tendo acompanhado o aparecimento de quase todas as formas de representação visual e tendo convivido “com todas as formas emergentes de imagem” no século XX (Oliveira & Pedro, 2011, p. 6), afirmou-se como um meio invisual, uma característica que muitas vezes o confundiu com um meio também invisível. Num livro de 1989, Peter Lewis e Jerry Booth falam desta invisibilidade como uma condição que se explica por uma certa tendência para subordinar a rádio à televisão em matéria de políticas públicas, subestimando-se o seu potencial como meio de comunicação e de difusão de conteúdos. Por outro lado, para os autores, a marginalização da rádio deve-se ao facto de os estudos de comunicação terem sempre considerado este meio num lugar menor da história dos média. A mesma ideia é retomada num texto do ano 2000, publicado por Peter Lewis no International Journal of Culture. Referindo-se ao estatuto cultural da rádio, o autor explica que ela tem sido um lugar de paixões privadas, mas ninguém o reconhece em público (Lewis, 2000).

A genetic perspective on African prehistory

The various genetic systems (mitochondrial DNA, the Y-chromosome and the genome-wide autosomes) indicate that Africa is the most genetically diverse continent in the world and the most likely place of origin for anatomically modern humans. However, where in Africa modern humans arose and how the current genetic makeup within the continent was shaped is still open to debate. Here, we summarize the debate and focus especially on the maternally inherited mitochondrial DNA (mtDNA) and a recently revised chronology for the African mtDNA tree. We discuss the possible origin of modern humans in southern, eastern or Central Africa; the possibility of a migration from southern to eastern Africa more than 100 ka, carrying lineages within mtDNA haplogroup L0; the evidence for a climate-change-mediated population expansion in eastern Africa involving mtDNA haplogroup L3, leading to the “out-of-Africa” migration around 70–60 ka; the re-population of North Africa from the Near East around 40–30 ka suggested by mtDNA haplogroups U6 and M1; the evidence for population expansions and dispersals across the continent at the onset of the Holocene ; and the impact of the Bantu dispersals in Central, eastern and southern Africa within the last few millennia.