118 resultados para limits of visual detection


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PURPOSE: To describe fundus autofluorescence (AF) patterns and their change over time in patients with age-related macular degeneration (AMD) and high risk of visual loss participating in the drusen laser study (DLS). DESIGN: Randomized clinical trial. METHODS: The study population consisted of 29 patients (35 eyes) participating in the DLS, which is a prospective, randomized, controlled clinical trial of prophylactic laser therapy in patients with AMD and high risk of neovascular complications. The intervention consisted of 16 eyes having prophylactic laser and 19 receiving no treatment. The main outcome measures were changes in the distribution of drusen and AF. Patients were reviewed for a median follow-up or 24 months (range 12-36 months). RESULTS: At baseline, four patterns of fundus AF were recognized: focal increased AF (n = 18), reticular AF (n = 3), combined focal and reticular AF (n = 2), and homogeneous AF (n = 12). At last follow-up, fundus AF remained unchanged in 15 untreated (78%) and in seven treated (43%) eyes. In only one untreated eye, focal areas of increased AF returned to background levels and were no longer detectable at last follow-up, compared with six treated eyes. This difference was statistically significant (P = .03). Only large foveal soft drusen (drusenoid pigment epithelium detachments) consistently corresponded with focal changes in AF, whereas no obvious correspondence was found between small soft drusen located elsewhere and changes in AF. CONCLUSION: The lack of obvious correspondence between the distribution of drusen and of AF found in this study appears to indicate that drusen and AF represent independent measures of aging in the posterior pole. © 2002 Elsevier Science Inc. All rights reserved.

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Purpose: To compare two fast threshold strategies of visual field assessment; SITA Fast (HSF) and Tendency Orientated Perimetry (TOP), in detecting visual field loss in patients with glaucoma. Methods: Seventy-six glaucoma, ocular hypertensive and normal patients had HSF and TOP performed in random order. Quantitative comparisons for the global visual field indices - mean deviation and defect (MD) for HSF and TOP, and pattern standard deviation (PSD) for HSF and loss variance (LV) for TOP - were made using correlation coefficients. Humphrey global parameters were converted to Octopus equivalents, and method comparison analysis was used to determine agreement between the two strategies. Test duration times were compared using t-test. Sensitivity and specificity for these two algorithms were determined according to predetermined criteria. Results: High correlation coefficient values were obtained for MD measurements between HSF and TOP (r=-0.89, P

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Political parties have only recently become a subject of investigation in political theory. In this paper I analyse religious political parties in the context of John Rawls’s political liberalism. Rawlsian political liberalism, I argue, overly constrains the scope of democratic political contestation and especially for the kind of contestation channelled by parties. This restriction imposed upon political contestation risks undermining democracy and the development of the kind of democratic ethos that political liberalism cherishes. In this paper I therefore aim to provide a broader and more inclusive understanding of ‘reasonable’ political contestation, able to accommodate those parties (including religious ones) that political liberalism, as customarily understood, would exclude from the democratic realm. More specifically, I first embrace Muirhead and Rosenblum’s (Perspectives on Politics 4: 99–108 2006) idea that parties are ‘bilingual’ links between state and civil society and I draw its normative implications for party politics. Subsequently, I assess whether Rawls’s political liberalism is sufficiently inclusive to allow the presence of parties conveying religious and other comprehensive values. Due to Rawls’s thick conceptions of reasonableness and public reason, I argue, political liberalism risks seriously limiting the number and kinds of comprehensive values which may be channelled by political parties into the public political realm, and this may render it particularly inhospitable to religious political parties. Nevertheless, I claim, Rawls’s theory does offer some scope for reinterpreting the concepts of reasonableness and public reason in a thinner and less restrictive sense and this may render it more inclusive towards religious partisanship.

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A survey of the use of the term democracy in Irish politics in the late eighteenth and early ninetenth centuries

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Many studies suggest a large capacity memory for briefly presented pictures of whole scenes. At the same time, visual working memory (WM) of scene elements is limited to only a few items. We examined the role of retroactive interference in limiting memory for visual details. Participants viewed a scene for 5?s and then, after a short delay containing either a blank screen or 10 distracter scenes, answered questions about the location, color, and identity of objects in the scene. We found that the influence of the distracters depended on whether they were from a similar semantic domain, such as "kitchen" or "airport." Increasing the number of similar scenes reduced, and eventually eliminated, memory for scene details. Although scene memory was firmly established over the initial study period, this memory was fragile and susceptible to interference. This may help to explain the discrepancy in the literature between studies showing limited visual WM and those showing a large capacity memory for scenes.

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Can the demos be uncoupled from the ethnos? Can there be a democratic politics of state‐boundaries, or are borders a condition of the possibility of democratic politics rather than a possible subject for those politics? The author argues for the decoupling strategy and affirms the possibility of a democratic politics about borders, anchoring the discussion in the politics of Northern Ireland. The argument turns on the analysis of public reasoning. It is argued first that culturalist accounts of self‐determination are misconceived and that political institutions, and not cultural identity, make collective self‐determination possible. Second, that the demos is constituted by acts of mutual recognition required by the practice of public reasoning, and that this practice cannot be confined with state‐boundaries. Taken together this allows us to conceive of the unity of a people as constituted by practices of public reason, given effect by institutions whose configuration is never finally fixed.

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This paper considers the enhancement of loss-of-mains detection by use of a differential rate-of-change-of-frequency relay to reduce nuisance tripping and improve sensitivity to small excursions in frequency. The telecommunications media which might carry the differential ROCOF signal are reviewed with a focus on channel latency, bandwidth and security.

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This paper discusses methods of using the Internet as a communications media between distributed generator sites to provide new forms of loss-of-mains protection. An analysis of the quality of the communications channels between several nodes on the network was carried out experimentally. It is shown that Internet connections in urban environments are already capable of providing real-time power system protection, whilst rural Internet connections are borderline suitable but could not yet be recommended as a primary method of protection. Two strategies of providing loss-of-mains across Internet protocol are considered, broadcast of a reference frequency or phasor representing the utility and an Internet based inter-tripping scheme.