Search results for "visual fields"
showing 10 items of 78 documents
Learning Curve and Fatigue Effect of Flicker Defined Form Perimetry
2011
To evaluate the learning curve and fatigue effect of flicker defined form (FDF) perimetry.Prospective cross-sectional study.One hundred forty-one eyes of 75 healthy subjects were included in the study. Every subject was measured 3 times on 3 different days within 3 months. Differences among the tests were analyzed for mean sensitivity (MS), mean deviation (MD), pattern standard deviation (PSD), reliability indices, test duration, and test points5% and0.5% in 75 right eyes on the basis of linear mixed models for repeated measurements. To assess the effect of fatigue, differences of MS, MD, and PSD values between 66 left and right eyes were evaluated regarding alterations between these 3 exam…
Chromatic and achromatic visual fields in relation to choroidal thickness in patients with high myopia: A pilot study
2018
Purpose. - To analyse the relationship between the choroidal thickness and the visual perception of patients with high myopia but without retinal damage. Methods. - All patients underwent ophthalmic evaluation including a slit lamp examination and dilated ophthalmoscopy, subjective refraction, best corrected visual acuity, axial length, optical coherence tomography, contrast sensitivity function and sensitivity of the visual pathways. Results. - We included eleven eyes of subjects with high myopia. There are statistical correlations between choroidal thickness and almost all the contrast sensitivity values. The sensitivity of magnocellular and koniocellular pathways is the most affected, an…
Modifying auditory perception with prisms? Aftereffects of prism adaptation on a wide auditory spectrum in musicians and nonmusicians
2021
Prism adaptation consists of pointing to visual targets while wearing prisms that shift the visual field laterally. The aftereffects are not restricted to sensorimotor level but extend to spatial cognition. There is a link between spatial representation and auditory frequency, with an association of low frequencies on the left side and high frequencies on the right side of space. The present study aimed first at evaluating the representation of auditory frequencies on a wide range of frequencies in musicians and nonmusicians. We used the ‘auditory interval bisection judgment’ within three auditory intervals. The results showed a pseudoneglect behavior in pretest in musicians and nonmusician…
Expectation of sensory stimulation modulates brain activation during visual motion stimulation.
2005
The differential effects of visual hemifield motion stimulation during fixation of a stationary target were compared under two conditions: fixation straight ahead without any further instructions and fixation straight ahead with attention shifted to the "dark hemifield." Data from nine right-handed volunteers revealed that striate and extrastriate right hemispheric visual areas exhibited larger activations during left hemifield motion stimulation when attention was shifted to the right dark hemifield. Montreal Neurological Institute (MNI) coordinates (26, -98, -4) of the additional clusters activated in the latter condition corresponded best to the kinetic occipital region, which is known t…
Are simple striate cells analysers of visual signals both in spatial position as well as in spatial frequency?
1984
According to a modern view, simple cells of the cat striate cortex are considered to operate as apart of Fourier analysis system thus leading to the idea that the operational mechanism of the visual cortex is concerned with the analysis of spatial frequencies. Nevertheless if simple cells are really concerned only with the analysis of spatial frequencies there should exist a strict relationship between their spatial frequency selectivity and the spatial organization of their receptive fields. This is because it is the spatial organization of the spatial frequency detector i.e. the cell's receptive field that determines the cell's spatial frequency selectivity. Since the quantitative analysi…
An overall description of retinotopic mapping in the cat's visual cortex areas 17, 18, and 19.
1985
Mathematical functions are derived which model the retinotopic mapping in the cat's visual cortical areas 17, 18, and 19. All three mappings are simple modifications of a complex power function with an exponent of 0.43. This function is decomposed so as to give an intermediate stage which is common to all three mappings and can be regarded as a model of the lateral geniculate nucleus mapping. The influence of retinotopic mapping on visual receptive fields was studied. The results show that a dependence of the receptive field properties on the position in the visual field is to be expected.
RELATIVISTIC COMPRESSION AND EXPANSION OF EXPERIENTIAL TIME IN THE LEFT AND RIGHT SPACE
2007
Time, space and numbers are closely linked in the physical world. However, the relativistic-like effects on time perception of spatial and magnitude factors remain poorly investigated. Here we wanted to investigate whether duration judgments of digit visual stimuli are biased depending on the side of space where the stimuli are presented and on the magnitude of the stimulus itself. Different groups of healthy subjects performed duration judgment tasks on various types of visual stimuli. In the first two experiments visual stimuli were constituted by digit pairs (1 and 9), presented in the centre of the screen or in the right and left space. In a third experiment visual stimuli were constitu…
Transposed-letter and laterality effects in lexical decision.
2006
Two divided visual field lexical decision experiments were conducted to examine the role of the cerebral hemispheres in transposed-letter similarity effects. In Experiment 1, we created two types of nonwords: nonadjacent transposed-letter nonwords (TRADEGIA; the base word was TRAGEDIA, the Spanish for TRAGEDY) and two-letter different nonwords (orthographic controls: TRATEPIA). In Experiment 2, the controls were one-letter different nonwords (TRAGEPIA) instead of two-letter different nonwords (TRATEPIA). The effect of transposed-letter similarity was substantially greater in the right visual field (left hemisphere) than in the left visual field. Furthermore, nonwords created by transposing …
Reliability and Intersession Agreement of Microperimetric and Fixation Measurements Obtained with a New Microperimeter in Normal Eyes.
2015
Purpose: To evaluate the reliability and intersession agreement of measurements of retinal sensitivity as well as of the fixation pattern obtained in healthy eyes with a microperimeter integrating the mechanism of the scanning laser ophthalmoscope (SLO) with the static perimetry. Methods: This study included a sample of 44 healthy eyes of 44 subjects of a mean age of 27.0 ± 8.5 years. In all cases, microperimetric exams with the MAIA system (Centervue, Padova, Italy) were performed in three different sessions to evaluate the intersession repeatability. The consistency of measurements was analyzed by using the Friedman test and by analyzing the correlation between consecutive measurements. A…
Normal Values for Microperimetry with the MAIA Microperimeter: Sensitivity and Fixation Analysis in Healthy Adults and Children
2017
Purpose To establish normative values of retinal sensitivity and parameters describing the fixation pattern using macular analyzer integrity assessment (MAIA) microperimetry (Centervue, Padova, Italy) in adults and children. Methods A sample of 237 eyes of 237 healthy subjects aged between 10 and 70 years (mean age 30.63 ± 16.23 years) was evaluated using the MAIA microperimeter. The following parameters provided by the MAIA device were evaluated: average threshold (AT), macular integrity, fixation indexes (P1% and P2%), bivariate contour ellipse area (BCEA) for 95% and 63% of points, and horizontal (H) and vertical (V) axes of the ellipse of fixation. Differences between different age-rela…