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Utilità dei potenziali evocati visivi nella diagnosi di patologie di interesse neuroftalmologico
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EOG Baseline Oscillation in Congenital Nystagmus
No full textVisual acuity in congenital nystagmus is primarily related to the duration of the foveation periods, during which the image of the target is placed on the fovea area and the eye velocity is low. This is true only if the subject is still able to place the target image on the centralmost fovea during the foveation period. In presence of a high variability of the foveation position the target image could not be placed on the centralmost fovea during many foveation periods. An associate vertical nystagmus or a slower horizontal eye movement combined to the horizontal nystagmus could cause such high variability. In several eye-movement recordings of patients affected by congenital nystagmus a very slow oculographic baseline fluctuations have been detected. In these patients the ability to foveate the target seems to depend mainly by the amplitude of the baseline fluctuation. The aim of this paper is to describe and quantitatively characterise these slow movements and try to associate them with the patient visual acuity. Furthermore a method to automatically separate the slow baseline oscillation from the nystagmus is proposed. Our findings suggest that for these patients the maximum effort could be concentrated on the reduction of the eye-position variability during foveatio
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
Eye Movement Baseline Oscillation and Variability of Eye Position During Foveation in Congenital Nystagmus
No full textDespite the inability to maintain steady fixation, congenital nystagmus does not necessarily reduce visual acuity, that can be achieved during the foveation periods. The duration of the foveation period, but also the cycle-tocycle variability of eye position and velocity during foveations play an important role. A quantitative relationship that relates visual acuity with foveation time and cycle-to-cycle variability of eye position during foveation has been previously proposed. In many infrared-oculographic and electro-oculographic eye position recordings of our database, a sinusoidal-like oscillation of the baseline was observed, on which the nystagmus waveforms lay. This oscillation may contribute to increase cycle-to-cycle variability during foveations. The aim of this work is to extract the baseline oscillation from the recordings and to verify its relationship with eye position variability during foveation. On the basis of the observations, the baseline oscillation was assumed to be sinusoidal, and was estimated (using a least mean square technique) from eye movement signals recorded during fixation intervals, at different gaze positions, from 20 patients affected by congenital nystagmus with low visual acuity. The average baseline oscillation amplitude was 1.31◦, while the average frequency was 0.34 Hz. Baseline oscillation amplitude was well correlated (with a coefficient of 0.66) to the standard deviations of eye-position during foveation, which in turn is connected to visual acuity
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