scholarly journals Foveal visual acuity is worse and shows stronger contour interaction effects for contrast-modulated than luminance-modulated Cs

2013 ◽  
Vol 30 (3) ◽  
pp. 105-120 ◽  
Author(s):  
MOHD IZZUDDIN HAIROL ◽  
MONIKA A. FORMANKIEWICZ ◽  
SARAH J. WAUGH
Keyword(s):  
Visual Acuity ◽  
Spatial Scales ◽  
Receptive Fields ◽  
Spatial Vision ◽  
Interaction Effects ◽  
Foveal Vision ◽  
Spatial Mechanisms ◽  
Visual Acuity Testing ◽  
Contour Interaction ◽  
Gap Width

AbstractContrast-modulated (CM) stimuli are processed by spatial mechanisms that operate at larger spatial scales than those processing luminance-modulated (LM) stimuli and may be more prone to deficits in developing, amblyopic, and aging visual systems. Understanding neural mechanisms of contour interaction or crowding will help in detecting disorders of spatial vision. In this study, contour interaction effects on visual acuity for LM and CM C and bar stimuli are assessed in normal foveal vision. In Experiment 1, visual acuity is measured for all-LM and all-CM stimuli, at ∼3.5× above their respective modulation thresholds. In Experiment 2, visual acuity is measured for Cs and bars of different type (LM C with CM bars and vice versa). Visual acuity is degraded for CM compared with LM Cs (0.46 ± 0.04 logMAR vs. 0.18 ± 0.04 logMAR). With nearby bars, CM acuity is degraded further (0.23 ± 0.01 logMAR or ∼2 lines on an acuity chart), significantly more than LM acuity (0.11 ± 0.01 logMAR, ∼1 line). Contour interaction for CM stimuli extends over greater distances (arcmin) than it does for LM stimuli, but extents are similar with respect to acuities (∼3.5× the C gap width). Contour interaction is evident when the Cs and bars are defined differently: it is stronger when an LM C is flanked by CM bars (0.17 ± 0.03 logMAR) than when a CM C is flanked by LM bars (0.08 ± 0.02 logMAR). Our results suggest that contour interaction for foveally viewed acuity stimuli involves feature integration, such that the outputs of receptive fields representing Cs and bars are combined. Contour interaction operates at LM and CM representational stages, it can occur across stage, and it is enhanced at the CM stage. Greater contour interaction for CM Cs and bars could hold value for visual acuity testing and earlier diagnosis of conditions for which crowding is important, such as in amblyopia.

scholarly journals Visual acuity and contour interaction for luminance-modulated and contrast-modulated Cs in normal foveal vision

2010 ◽  
Vol 10 (7) ◽  
pp. 1332-1332
Author(s):  
M. I. Hairol ◽  
M. A. Formankiewicz ◽  
S. J. Waugh
Keyword(s):  
Visual Acuity ◽  
Foveal Vision ◽  
Contour Interaction

Preliminary results of visual acuity testing in an African elephant

1997 ◽  
Author(s):  
Melissa R. Shyan ◽  
Jeff Peterson ◽  
Barbara Milankow ◽  
Robert H. I. Dale
Keyword(s):  
Visual Acuity ◽  
African Elephant ◽  
Preliminary Results ◽  
Visual Acuity Testing

scholarly journals Fixation Preference and Visual Acuity Testing in a Population-based Cohort of Preschool Children with Amblyopia Risk Factors

Ophthalmology ◽  
2009 ◽  
Vol 116 (1) ◽  
pp. 145-153 ◽  
Author(s):  
Susan A. Cotter ◽  
Kristina Tarczy-Hornoch ◽  
Erin Song ◽  
Jesse Lin ◽  
Mark Borchert ◽  
...  
Keyword(s):  
Risk Factors ◽  
Visual Acuity ◽  
Preschool Children ◽  
Population Based ◽  
Visual Acuity Testing ◽  
Fixation Preference

scholarly journals Visual performance in behaving cats after prenatal unilateral enucleation

1993 ◽  
Vol 90 (23) ◽  
pp. 11142-11146 ◽  
Author(s):  
S Bisti ◽  
C Trimarchi
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
Receptive Field ◽  
Receptive Fields ◽  
Direction Selectivity ◽  
Visual Performance ◽  
Field Size ◽  
Electrophysiological Recordings ◽  
Severe Impairment ◽  
Orientation Columns

Prenatal unilateral enucleation in mammals causes an extensive anatomical reorganization of visual pathways. The remaining eye innervates the entire extent of visual subcortical and cortical areas. Electrophysiological recordings have shown that the retino-geniculate connections are retinotopically organized and geniculate neurones have normal receptive field properties. In area 17 all neurons respond to stimulation of the remaining eye and retinotopy, orientation columns, and direction selectivity are maintained. The only detectable change is a reduction in receptive field size. Are these changes reflected in the visual behavior? We studied visual performance in cats unilaterally enucleated 3 weeks before birth (gestational age at enucleation, 39-42 days). We tested behaviorally the development of visual acuity and, in the adult, the extension of the visual field and the contrast sensitivity. We found no difference between prenatal monocularly enucleated cats and controls in their ability to orient to targets in different positions of the visual field or in their visual acuity (at any age). The major difference between enucleated and control animals was in contrast sensitivity:prenatal enucleated cats present a loss in sensitivity for gratings of low spatial frequency (below 0.5 cycle per degree) as well as a slight increase in sensitivity at middle frequencies. We conclude that prenatal unilateral enucleation causes a selective change in the spatial performance of the remaining eye. We suggest that this change is the result of a reduction in the number of neurones with large receptive fields, possibly due to a severe impairment of the Y system.

Comparison of structural, functional, tonometric, and visual acuity testing for glaucoma: a prospective diagnostic accuracy study

2021 ◽  
Author(s):  
Rajesh S. Kumar ◽  
B. Ramgopal ◽  
Mahalakshmi V. Rackenchath ◽  
Sathi Devi A V ◽  
Suria S. Mannil ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Diagnostic Accuracy ◽  
Diagnostic Accuracy Study ◽  
Accuracy Study ◽  
Visual Acuity Testing

scholarly journals Modulations of foveal vision associated with microsaccade preparation

2020 ◽  
Vol 117 (20) ◽  
pp. 11178-11183
Author(s):  
Natalya Shelchkova ◽  
Martina Poletti
Keyword(s):  
Eye Movements ◽  
Visual Discrimination ◽  
Target Location ◽  
Onset Time ◽  
Spatial Vision ◽  
Saccade Target ◽  
Foveal Vision ◽  
Movement Onset ◽  
High Acuity ◽  
Gaze Position

It is known that attention shifts prior to a saccade to start processing the saccade target before it lands in the foveola, the high-resolution region of the retina. Yet, once the target is foveated, microsaccades, tiny saccades maintaining the fixated object within the fovea, continue to occur. What is the link between these eye movements and attention? There is growing evidence that these eye movements are associated with covert shifts of attention in the visual periphery, when the attended stimuli are presented far from the center of gaze. Yet, microsaccades are primarily used to explore complex foveal stimuli and to optimize fine spatial vision in the foveola, suggesting that the influences of microsaccades on attention may predominantly impact vision at this scale. To address this question we tracked gaze position with high precision and briefly presented high-acuity stimuli at predefined foveal locations right before microsaccade execution. Our results show that visual discrimination changes prior to microsaccade onset. An enhancement occurs at the microsaccade target location. This modulation is highly selective and it is coupled with a drastic impairment at the opposite foveal location, just a few arcminutes away. This effect is strongest when stimuli are presented closer to the eye movement onset time. These findings reveal that the link between attention and microsaccades is deeper than previously thought, exerting its strongest effects within the foveola. As a result, during fixation, foveal vision is constantly being reshaped both in space and in time with the occurrence of microsaccades.

A Survey of Visual Acuity Testing in the Infant and Preverbal Child

1984 ◽  
Vol 34 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Arthur L. Rosenbaum ◽  
David G. Kirschen
Keyword(s):  
Visual Acuity ◽  
Visual Acuity Testing

Pediatric Visual Acuity Testing

2022 ◽  
pp. 44-66
Author(s):  
Gayathri Srinivasan
Keyword(s):  
Visual Acuity ◽  
Scientific Evidence ◽  
Visual Behavior ◽  
Infants And Toddlers ◽  
Older Children ◽  
Commercial Products ◽  
Essential Component ◽  
Visual Acuity Testing ◽  
Set Up ◽  
Objective Visual Acuity

Visual acuity measurement is an essential component of any eye exam. In adults and older children, letter-based acuity (i.e., recognition acuity) is commonly used to measure vision. However, in infants and toddlers, performing traditional visual acuity testing is nearly impossible. Instead, modified optotypes such as gratings and pictures are shown to observe the young child's visual behavior. Additionally, there are objective visual acuity methods that negate the need for observing visual behavior. For the practicing clinician, the choices are many and can be confusing. With new commercial products coming into the market every day, it is nearly impossible to comprehensively cover each one of them. Instead, in this chapter, commonly used and/or studied visual acuity tests are covered. For each test, the set-up, procedure, documentation, and scientific evidence supporting or negating its use are discussed.

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