Purpose: A four-month extended wear clinical trial was conducted to compare the ocular effects of a high Dk Balafilcon A silicone hydrogel lens and a low Dk HEMA 38.6 per cent H, O soft lens. Method Twenty-four subjects who were adapted to daily wear of soft lenses wore a high Dk lens in one eye and a low Dk HEMA lens in the other eye for four months on an extended wear basis after one week of daily wear. Thirteen progress evaluations were conducted using standard clinical procedures.Results: Eighteen subjects (75 per cent) completed the study. The high Dk lens induced significantly less bulbar and limbal injection and corneal vascularisation than the low Dk HEMA lens (p < 0.05). Epithelial microcysts were observed only in the eyes wearing the low Dk lens. A significant increase in myopia was found in the eyes wearing the low Dk HEMA lens (mean = 0.50 D, p < 0.01) compared to the insignificant myopic increase of 0.06 D in the eyes wearing the high Dk lens. Three subjects developed small infiltrates in the high Dk lens wearing eyes and significantly more post-lens debris was observed under the high Dk lens. Six subjects developed papillary conjunctivitis in the eye wearing silicone hydrogel lenses but only two of those were discontinued from the study. Conclusion:No hypoxia-related effects were observed with extended wear of the high Dk Balafilcon A silicone hydrogel lens.
Paracontrast and metacontrast magnitudes were measured in a target identification task. A particular class of illusory contours is described that did not mask in the paracontrast condition but did show a large metacontrast magnitude. The discontinuity in the masking function is interpreted in terms of the Fourier decomposition of the visual scene that is performed by cells selectively responsive to discrete bands of spatial frequencies. The class of contours that we describe can only mask through inhibition generated by their low spatial frequencies. These results are consistent with recent models of masking based on two independent modes of inhibition-within sustained visual channels, and between sustained and transient visual channels.One of the most important developments in visual psychophysics has been the discovery and classification of cells that are selectively responsive to different bands of spatial frequencies. Psychophysical and electrophysiological measurements (for reviews, see Breitmeyer, 1984;De Valois & De Valois, 1980;Graham, 1981;Shapley & Lennie, 1985; chap. 4) give evidence that the visual scene is represented in early vision in terms of a coarse Fourier decomposition, and that different pieces of the spectrum are processed by independent channels. Recently these ideas have been introduced into a theoretical framework for visual pattern masking (Breitmeyer, 1984;Breitmeyer & Ganz, 1976).Pattern masking is a phenomenon in which perceived contrast or clarity of contour for one stimulus decreases as a result of the presentation of a second stimulus. In paracontrast (mask precedes target) and metacontrast (target precedes mask) masking, there is no overlap between mask and target contour. In this paradigm, it is generally possible to identify that a target has been shown, even when the target suffers contrast reduction and blurring (Breitmeyer, 1984). The loss of contour detail and contrast without complete elimination of stimulus detection suggests that masking operates by differentially affecting the processing of the high-spatial-frequency content of the stimulus. The central idea of Breitmeyer and Ganz's (1976) theory is that there are two independent modes of inhibition acting on the channels that process high spatial frequencies. According to this theory, paracontrast masking is achieved primarily by intrachannel inhibition caused by an antagonistic center-surround interaction within the The authors wish to thank Jack McArdle for several helpful discussions concerning the experimental design and analysis of the data. We also want to acknowledge conversations with Dennis Proffitt and the advice and encouragement he offered. D.G. was supported by NIH Grant HD0703tH>1 during the course of this work. Address correspondence to David Gilden, Department of Psychology, Gilmer Hall, University of Virginia, Charlottesville, VA 22903-2477. receptive field of a single cell. It is theorized that metaeontrast masking is produced by center-surround interactions (as in paracontrast) and by an addition...
Objective: Undetected vision problems in children can lead to permanent vision loss, a condition known as amblyopia. Early detection and treatment of the causes of amblyopia may prevent this vision loss. The objective of this paper is to look for evidence that comprehensive eye examinations upon entry to junior Kindergarten are an effective way to identify and treat vision problems early. methods: Relevant peer-reviewed publications on amblyopia and the importance of comprehensive eye examinations were reviewed. Specific areas investigated include: the prevalence and causes of amblyopia; impact of vision problems on child development and education; impact of amblyopia and/or strabismus on quality of life; and the cost effectiveness of treating amblyopia. The validity of vision screening compared to a comprehensive eye examination was also reviewed. Synthesis:The review suggests that without a complete eye examination many eye or vision problems remain undetected at school entry. Left uncorrected these problems negatively impact child development, education and quality of life. Reduced vision due to amblyopia also restricts future employment opportunities and increases the risk of bilateral visual impairment in adulthood. Examination procedures with high sensitivity and specificity are required to accurately detect these problems. Studies show that amblyopia treatment initiated at an early age is one of the most cost-effective of all health interventions. Conclusion: There is good evidence in the literature that a full eye examination is critical to detect all cases of amblyopia. This and other visual problems can be detected and managed at an early age, which leads to better visual quality of life and economical outcomes. The Eye See Eye Learn program offers the “gold standard” of eye care.
In March 1998 the European Union (EU) formally launched a negotiation process by which to further enlarge the EU, having, in the preceding years, invited several former Soviet-influenced countries from Central and Eastern Europe (CEE), along with Cyprus, Malta and Turkey, to participate in accession to the EU if they so wished. This is the second of two articles concerned with Lithuania’s accession to the EU, the process of approximating EU environmental law and the legislative intricacies involved therein. The first paper critiqued the process of enlargement of the European Union from a largely pragmatic legal perspective through a legal case-study examination of Lithuania’s efforts in approximating the environmental acquis into national law. Lithuania was an accession state from Central Europe and acceded to the EU on 1 May 2004. The first paper provided insight into and guidance upon the process of the approximation of environmental law as it may relate, or has related, to other accession countries. It highlights the practical steps and the route of accession to the EU along with the legal requirements contained therein.This second paper focuses more specifically upon the actual implementation and related strategic aspects revealed in Lithuania’s efforts to approximate EU environmental law by reference to best practice, as developed by the lead author, for the EU.
Objectifs : Chez les enfants, les problèmes de vision non détectés peuvent entraîner une perte permanente de la vision, problème appelé amblyopie. La détection et le traitement précoces des causes de l’amblyopie peuvent éviter cette perte de vision. Cette communication vise à chercher des éléments probants démontrant que les examens complets de la vue au moment de l’entrée en prématernelle constituent un moyen efficace de repérer et de traiter rapidement les problèmes de vision. Méthodes : Nous avons étudié des publications pertinentes critiquées par des pairs portant sur l’amblyopie et sur l’importance des examens complets de la vue. Les aspects précis étudiés comprennent la prévalence et les causes de l’amblyopie, l’effet des problèmes de vision sur le développement et l’éducation de l’enfant, l’effet de l’amblyopie ou du strabisme sur la qualité de vie et la rentabilité du traitement de l’amblyopie. Nous avons évalué aussi la validité de ces tests de dépistage comparativement à l’examen complet de la vue. Résumé : L ’étude indique que sans examen complet de la vue, beaucoup de problèmes oculovisuels ne sont pas détectés à l’arrivée de l’enfant à l’école. S’ils ne sont pas corrigés, ces problèmes ont un effet négatif sur le développement, l’éducation et la qualité de vie de l’enfant. La baisse de la vue causée par l’amblyopie limite aussi les possibilités d’emploi futures et accroît le risque de déficience visuelle bilatérale chez l’adulte. Des méthodes d’examen très sensibles et spécifiques s’imposent pour repérer ces problèmes avec précision. Des études montrent que le traitement de l’amblyopie à un jeune âge constitue une des interventions les plus rentables en santé. Conclusion : Les publications contiennent de bons éléments de preuve indiquant qu’un examen complet de la vue joue un rôle crucial dans la détection de tous les cas d’amblyopie. Il est possible de détecter et de traiter l’amblyopie et d’autres problèmes de vision à un jeune âge, ce qui améliore les résultats reliés à la vue, à la qualité de vie et à l’économie. Le programme Eye See Eye Learn offre « l'étalon-or » des soins oculovisuels.
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