1,720,965 research outputs found
The papillary arterio-venous passage time (PAVPT) in normal subjects and in glaucomatous eyes
No full textHeritability of myopic refractive errors in identical and fraternal twins.
No full textThe existence of a visual feedback control of eye growth in humans is controversial, as the contributions of genetic and environmental factors are still unknown. To evaluate the heritability of refractive defects, we measured ocular refraction in 19 monozygote and 20 dizygote twin pairs (mean age 5 years). Monozygosity was ascertained by a common chorion, similarity of somatic traits, and identical dermatogliphes and was confirmed in myopes by blood marker diagnosis. Ocular refractive defects and axial length were evaluated by cycloplegic autorefractometry and biometry. By comparing identical and fraternal twins heritability of refractive defects was estimated to be 0.08-0.14; this low value indicates that the observed variability in refractive errors is nongenetic in origin. Three monozygote pairs were anisomyopic; differences between eyes in identical twins were related to the increased axial length of myopic eyes. In one eye, myopia was attributed to visual deprivation induced by a congenital cataract, while in five eyes it was correlated directly to the degree of astigmatic defects. The discordant axial length observed in monozygote twins is nongenetic. In agreement with previous findings reported in the literature, it is proposed that visual impoverishment of retinal images may play an early regulatory role in postnatal eye growth
Frame by frame dilution analysis of ICG angiography: a new method to measure choridal blood flow in glaucoma
No full textPurposes: To identify a new method of choroidal blood flow analysis in glaucomatous
patients. Methods: Twenty-four glaucomatous patients (G), 15 subjects with normal
tensional glaucoma (NTG) and 26 age-matched controls were recruited for the study.
They were submitted to dynamic indocyanine green angiography (ICGA) with a scanning
laser ophthalmoscope (SLO) (Rodenstock, Munchen, Germany). The choroidal filling
phases were digitized and stored in a computer. Twenty-five frames per second were
obtained. Each frame was elaborated by means of a “ threshold technique ” in order to
obtain black or white pixels. The area occupied by the white pixels in a field of 35° of
the choroid surrounding the disc was measured. The data obtained from each frame
were plotted versus time in order to obtain a “ frame-by-frame ” dilution curve. The 10%
filling time and the 55% filling time were compared among the three groups. Results:
NTG and G groups showed a significantly delayed filling time of the posterior choroid
when compared to the controls (10% filling time, p<0.01; 55% filling time, p<0.05). No
statistical difference between NTG and G could be observed. Conclusions: These data
suggest that an altered choroidal blood flow can play a role in the pathogenesis of
glaucoma.
CR: None -
FRAME BY FRAME ANGIOGRAPHY
No full textVolume monografia in lingua italiano/ inglese per il 78°congresso S.O.I del 18-21 novembre 199
Arterio-venous transit time in the superficial layer of the optic nerve head: A new parameter of glaucomatous damage
No full textPurpose:To evaluate arterio-venous transit time (AVTT) of the superficial layer of the optic nerve head (ONH) in primary open angle glaucoma (POAG).
Methods:Circulation times of the superficial layer of the ONH were quantified - in 35 POAG and 35 age-matvhed controls - using an objective, electronic guided examination of a high speed dynamic fluorescein angiography. AVTT of the superficial layer of the ONH was compared between groups, and vs ONH morphology and visual field defects.
Results: AVTT of the superficial layer of the ONH was significantly: higher in POAG patients vs controls ( 2.28 vs 1.29 sec; p< .001), and related to ONH morphology and field defects.
Conclusion: AVTT of the superficial layer of the ONH may be exactly quantified and may represent a new, objective parameter of glaucomatous damage
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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