The variation of resolution and of ommatidial dimensions in the compound eyes of the fiddler crab Uca lactea annulipes (Ocypodidae, Brachyura, Decapoda)

1996 ◽  
Vol 199 (7) ◽  
pp. 1569-1577 ◽  
Author(s):  
J Zeil ◽  
M Al-Mutairi
Keyword(s):  
Visual Field ◽  
Fiddler Crab ◽  
Visual Fields ◽  
Horizontal Resolution ◽  
Resolving Power ◽  
Compound Eyes ◽  
Vertical Resolution ◽  
Histological Techniques ◽  
Uca Lactea

We studied variations in the optical properties of the compound eyes of Uca lactea annulipes using in vivo optical and histological techniques. The distribution of resolving power in the eyes of this fiddler crab species is typical for arthropods that inhabit flat environments: the eyes possess a panoramic equatorial acute zone for vertical resolution and a steep decrease of resolution away from the eye equator in the dorsal and ventral visual fields. The dimensions of the cellular components of the ommatidia vary accordingly: in the equatorial part of the eyes, facets are larger, and crystalline cones and rhabdoms are longer than in the dorsal and ventral parts of the eyes. Along the eye equator, horizontal resolution is low compared with vertical resolution and varies little throughout the visual field. The eyes of Uca lactea annulipes are unusual in that the gradient of vertical anatomical and optical resolution is steeper in the dorsal than in the ventral visual field. We interpret this difference as indicating that the information content of the world as seen by the crabs differs above and below the horizon line in specific and predictable ways.

Visual fields of the compound eyes of four species of Cicindelidae (Coleoptera)

1980 ◽  
Vol 58 (3) ◽  
pp. 326-336 ◽  
Author(s):  
J. E. Kuster ◽  
W. G. Evans
Keyword(s):  
Visual Field ◽  
North American ◽  
Visual Fields ◽  
Morphological Characters ◽  
Head Size ◽  
Compound Eyes ◽  
Eye Size ◽  
Nocturnal Species ◽  
The Relationship ◽  
Diurnal Species

Visual field angles were measured around the circumference of the compound eyes of four species of North American Cicindelidae and plotted on Mollweide homolographs. Areas of monoscopic and stereoscopic visual fields and blind areas were calculated. In contrast to the nocturnal species (Amblycheila schwarzi and Omus californicus), the crepuscular species (Megacephala Carolina) and the diurnal species (Cicindela tranquebarica) have more ommatidia and larger eye size: head size ratios, total visual fields, and stereoscopic visual fields. These characters are considered to be derived and confirm the phylogenetic sequence of the four genera that was previously based on other morphological characters. The relationship between these characters and the biology of each species is also discussed.

scholarly journals Trilobite vision: a comparison of schizochroal and holochroal eyes with the compound eyes of modern arthropods

1992 ◽  
Vol 6 ◽  
pp. 103-103
Author(s):  
David. Fordyce ◽  
Thomas W. Cronin
Keyword(s):  
Visual Field ◽  
National Science Foundation ◽  
Compound Eye ◽  
Visual Fields ◽  
Visual Space ◽  
Compound Eyes ◽  
Central Processing ◽  
Corneal Lens ◽  
Bright Sunlight ◽  
Parameter Values

The compound eyes of trilobites provide the best examples of fossilized sensory organs for which the function in life can be worked out today, because the optical array of their corneal lenses preserves the geometry with which the eye originally sampled the visual world. An analysis of trilobite vision is strengthened by the use of new mathematical approaches to compound eye design. In particular, the product of the facet diameter (D) and the interommatidial angle (Δϕ) gives the value of the eye parameter, DΔϕ, which is a reliable indicator of the photic conditions in which the eye was used. In modern arthropods, DΔϕ values range from 0.3 for animals active in bright sunlight to 20 or more for nocturnal or deep-sea animals.Three types of compound eyes existed in trilobites: schizochroal, holochroal, and abathochroal. We examined the schizochroal and holochroal types. Schizochroal eyes were studied in the phacopid species Phacops rana crassituberculata and Phacops rana milleri. We measured the diameter of every corneal lens, and estimated its optical axis by taking the normal to the plane of the lens's diameter. In both species, each eye covered almost exactly 180° of visual space in azimuth with no binocular overlap, from directly anterior to directly posterior. Vertically, the visual field extended from the horizon to about 40° in elevation. Facet diameters and interommatidial angles were large, giving eye parameter values ranging from 10 to > 150. These are much greater than in any living arthropod, implying that modern compound eye theory does not apply to schizochroal eyes. We believe that each ommatidium of the schizochroal eye served as a miniature lens eye. If so, phacopid vision must have been unique, with multiply overlapping visual fields. Such a design would have required considerable central processing, but could have provided exceptional opportunities for spatial, spectral, and polarizational analysis.We examined holochroal compound eyes in Asaphus cornutus and Isotelus “gigas”. Here, visual field coverage was greater than in the schizochroal eye type, with a small amount of frontal binocular overlap. Holochroal eyes contain far more ommatidia than do schizochroal types, reducing both facet diameter (D) and interommatidial angle (Δϕ). Thus, DΔϕ values in these species fall into the same range as in modern compound eyes. This implies that function of the holochroal eye was similar to that of modern crustaceans and insects.This material is based on research supported by the National Science Foundation under Grants No. BNS-8518769 and BNS-8917183.

019 Correlation of visual field loss with mri findings in patients with pituitary tumours

2018 ◽  
Vol 89 (6) ◽  
pp. A9.1-A9
Author(s):  
Christian J Lueck ◽  
Emily Kane ◽  
David Ashton ◽  
Peter Mews ◽  
Kate Reid ◽  
...  
Keyword(s):  
Finite Element ◽  
Visual Field ◽  
Contact Area ◽  
Visual Fields ◽  
Visual Field Loss ◽  
Optic Chiasm ◽  
Pituitary Tumours ◽  
Mri Findings ◽  
Chiasmal Compression

IntroductionThe exact mechanism that gives rise to bi-temporal hemianopia in chiasmal compression by pituitary tumours is currently unknown. One theory suggests that, because crossing fibres cross each other and therefore have less contact area, they experience greater stress from compressive forces than those experienced by uncrossed fibres (which have a larger contact area). Finite element modelling has been used has been used to investigate this in silico but the hypothesis needs testing in vivo. This study aimed to determine whether extrinsic chiasmal compression was associated with patterns of visual field loss which supported the ‘crossing hypothesis’ or not.MethodsSubjects with chiasmal compression secondary to pituitary tumours who also had clear visual field abnormalities were identified from the Canberra Hospital database. Visual fields were analysed to derive ‘temporality’ and ‘bi-temporality’ indices. MRI scans were analysed to determine the relative elevations of centre and peripheral portions of the optic chiasm and, in turn, the eccentricity of compression. Temporality indices were plotted against central chiasmal elevation, and both temporal and nasal hemi-field abnormalities were plotted against eccentricity.Results122 patients were identified but only 12 were suitable for analysis. Both temporality and bi-temporality indices were significantly correlated with central chiasmal elevation (p=0.004). Hemi-field studies demonstrated patterns of visual loss with increasing eccentricity that were more consistent with the ‘crossing hypothesis’ though the correlations failed to reach significance.ConclusionThis study provides tentative support for the ‘crossing hypothesis’. The information will be used to inform further finite element models of chiasmal compression. A larger, prospective study is warranted.

Visual Field Accuracy and Eye Movement Direction: A Child's Eye View

1980 ◽  
Vol 50 (2) ◽  
pp. 631-636
Author(s):  
Evans Mandes
Keyword(s):  
Eye Movements ◽  
Visual Field ◽  
Eye Movement ◽  
Visual Fields ◽  
Movement Direction

Post-exposural eye movements were studied in 32 adults and 24 7-yr.-old children. Stimuli were binary figures exposed tachistoscopically in both visual fields simultaneously. The data showed significant correlations between direction of eye movement and locus of recognition for both children and adults. No significant differences were found in frequencies of eye movements of children and adults. The data are interpreted in terms of the facilitative effects of post-exposural eye movements upon perception for both groups.

scholarly journals Myelin densities in retinotopically defined dorsal visual areas of the macaque

2021 ◽  
Author(s):  
Xiaolian Li ◽  
Qi Zhu ◽  
Wim Vanduffel
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Cortical Thickness ◽  
New World Monkeys ◽  
Isotropic Resolution ◽  
Density Mapping ◽  
Area V2 ◽  
Visual Areas ◽  
Density Results

AbstractThe visuotopic organization of dorsal visual cortex rostral to area V2 in primates has been a longstanding source of controversy. Using sub-millimeter phase-encoded retinotopic fMRI mapping, we recently provided evidence for a surprisingly similar visuotopic organization in dorsal visual cortex of macaques compared to previously published maps in New world monkeys (Zhu and Vanduffel, Proc Natl Acad Sci USA 116:2306–2311, 2019). Although individual quadrant representations could be robustly delineated in that study, their grouping into hemifield representations remains a major challenge. Here, we combined in-vivo high-resolution myelin density mapping based on MR imaging (400 µm isotropic resolution) with fine-grained retinotopic fMRI to quantitatively compare myelin densities across retinotopically defined visual areas in macaques. Complementing previously documented differences in populational receptive-field (pRF) size and visual field signs, myelin densities of both quadrants of the dorsolateral posterior area (DLP) and area V3A are significantly different compared to dorsal and ventral area V3. Moreover, no differences in myelin density were observed between the two matching quadrants belonging to areas DLP, V3A, V1, V2 and V4, respectively. This was not the case, however, for the dorsal and ventral quadrants of area V3, which showed significant differences in MR-defined myelin densities, corroborating evidence of previous myelin staining studies. Interestingly, the pRF sizes and visual field signs of both quadrant representations in V3 are not different. Although myelin density correlates with curvature and anticorrelates with cortical thickness when measured across the entire cortex, exactly as in humans, the myelin density results in the visual areas cannot be explained by variability in cortical thickness and curvature between these areas. The present myelin density results largely support our previous model to group the two quadrants of DLP and V3A, rather than grouping DLP- with V3v into a single area VLP, or V3d with V3A+ into DM.

scholarly journals Functional visual fields: relationship of visual field areas to self-reported function

2017 ◽  
Vol 37 (4) ◽  
pp. 399-408 ◽  
Author(s):  
Hikmat Subhi ◽  
Keziah Latham ◽  
Joy Myint ◽  
Michael D. Crossland
Keyword(s):  
Visual Field ◽  
Visual Fields ◽  
Relationship Of

Hemispheric Specialization for Processing Chinese Characters: Some Evidence from Lexical Decision Vocal Reaction Times

1989 ◽  
Vol 69 (3_suppl) ◽  
pp. 1083-1089 ◽  
Author(s):  
Michael P. Rastatter ◽  
Gail Scukanec ◽  
Jeff Grilliot
Keyword(s):  
Visual Field ◽  
Lexical Decision ◽  
Hemispheric Specialization ◽  
Visual Fields ◽  
Reaction Times ◽  
Decision Processes ◽  
Right Visual Field ◽  
Chinese Characters ◽  
Error Type ◽  
Chinese Subjects

Lexical decision vocal reaction times (RT) were obtained for a group of Chinese subjects to unilateral tachistoscopically presented pictorial, single, and combination Chinese characters. The RT showed a significant right visual-field advantage, with significant correlations of performance between the visual fields for each type of character. Error analysis gave a significant interaction between visual fields and error type—significantly more false positive errors occurred following left visual-field inputs. These results suggest that the left hemisphere was responsible for processing each type of character, possibly reflecting superior postaccess lexical-decision processes.

Review lecture: Apposition eyes of large diurnal insects as organs adapted to seeing

1980 ◽  
Vol 207 (1168) ◽  
pp. 287-309 ◽  
Keyword(s):  
Nodal Point ◽  
Visual Fields ◽  
Photoreceptor Cells ◽  
Resolving Power ◽  
Field Size ◽  
Correct Position ◽  
Anatomical Arrangement ◽  
Angular Coordinates ◽  
And Function ◽  
Facet Size

(1) The fields of view of the photoreceptor cells are determined by the dimensions and anatomical arrangement of the optical part of the ommatidium. The dimensions, and therefore the fields of view of the ommatidia are also related across the eye. In the relation between structure and function there are many points that invite discussion, but the intention is to order our knowledge so that the gaps become obvious. (2) The first step has been to make maps of the eyes showing the maximum theoretical resolving power of the facets and also the interommatidial angle, the reciprocal of which is the maximum spatial resolution of combinations of facets. The ratio of these two resolutions at each point shows the minimum overlap of the visual fields. These maps can be made from the outside of the eye; they show the main types of eye. (3) The next step is to work out the optics of individual ommatidia so that the focal lengths and receptor widths can be measured. The field width can then be predicted from the facet size and the subtense of the receptor at the posterior nodal point. The final step is to measure the field widths of individual ommatidia experimentally as a test of the optical theory, and to make maps of the actual fields in their correct position on the eye in angular coordinates. (4) Three examples of maps of actual fields are given, and their anato­mical and diffraction components are separated. The maps are an essential step towards the electrophysiological analysis of the ganglia behind the eye. A theory of the origin of the fields in terms of anatomy and optics also opens the way to an analysis of mechanisms that change the field size upon adaptation to light. A comparative study of the fields in different eye regions and in different species can also be related to visual habits and behaviour.

Long-term visual outcome after microsurgical removal of occipital lobe cavernomas

2012 ◽  
Vol 117 (2) ◽  
pp. 295-301 ◽  
Author(s):  
Juri Kivelev ◽  
Elina Koskela ◽  
Kirsi Setälä ◽  
Mika Niemelä ◽  
Juha Hernesniemi
Keyword(s):  
Visual Field ◽  
Visual Fields ◽  
Visual Field Loss ◽  
Occipital Lobe ◽  
Visual Outcome ◽  
Surgical Removal ◽  
Long Term Outcome ◽  
Visual Field Deficit

Object Cavernomas in the occipital lobe are relatively rare. Because of the proximity to the visual cortex and incoming subcortical tracts, microsurgical removal of occipital cavernomas may be associated with a risk of visual field defects. The goal of the study was to analyze long-term outcome after operative treatment of occipital cavernomas with special emphasis on visual outcome. Methods Of the 390 consecutive patients with cavernomas who were treated at Helsinki University Central Hospital between 1980 and 2011, 19 (5%) had occipital cavernomas. Sixteen patients (4%) were surgically treated and are included in this study. The median age was 39 years (range 3–59 years). Seven patients (56%) suffered from hemorrhage preoperatively, 5 (31%) presented with visual field deficits, 11 (69%) suffered from seizures, and 4 (25%) had multiple cavernomas. Surgery was indicated for progressive neurological deterioration. The median follow-up after surgery was 5.25 years (range 0.5–14 years). Results All patients underwent thorough neuroophthalmological assessment to determine visual outcome after surgery. Visual fields were classified as normal, mild homonymous visual field loss (not disturbing the patient, driving allowed), moderate homonymous visual field loss (disturbing the patient, driving prohibited), and severe visual field loss (total homonymous hemianopia or total homonymous quadrantanopia). At the last follow-up, 4 patients (25%) had normal visual fields, 6 (38%) had a mild visual field deficit, 1 (6%) complained of moderate visual field impairment, and 5 (31%) had severe homonymous visual field loss. Cavernomas seated deeper than 2 cm from the pial surface carried a 4.4-fold risk of postoperative visual field deficit relative to superficial ones (p = 0.034). Six (55%) of the 11 patients presenting with seizures were seizure-free postoperatively. Eleven (69%) of 16 patients had no disability during the long-term follow-up. Conclusions Surgical removal of occipital cavernomas may carry a significant risk of postoperative visual field deficit, and the risk is even higher for deeper lesions. Seizure outcome after removal of these cavernomas appeared to be worse than that after removal in other supratentorial locations. This should be taken into account during preoperative planning.

On the Relation between Visual Spatial Attention and Visual Field Asymmetries

1992 ◽  
Vol 44 (3) ◽  
pp. 529-555 ◽  
Author(s):  
T. A Mondor ◽  
M.P. Bryden
Keyword(s):  
Visual Field ◽  
Visual Attention ◽  
Visual Fields ◽  
Stimulus Onset ◽  
Right Visual Field ◽  
Structural Factors ◽  
Letter Identification ◽  
Functional Capabilities ◽  
Visual Spatial ◽  
The Right

In the typical visual laterality experiment, words and letters are more rapidly and accurately identified in the right visual field than in the left. However, while such studies usually control fixation, the deployment of visual attention is rarely restricted. The present studies investigated the influence of visual attention on the visual field asymmetries normally observed in single-letter identification and lexical decision tasks. Attention was controlled using a peripheral cue that provided advance knowledge of the location of the forthcoming stimulus. The time period between the onset of the cue and the onset of the stimulus (Stimulus Onset Asynchrony—SOA) was varied, such that the time available for attention to focus upon the location was controlled. At short SO As a right visual field advantage for identifying single letters and for making lexical decisions was apparent. However, at longer SOAs letters and words presented in the two visual fields were identified equally well. It is concluded that visual field advantages arise from an interaction of attentional and structural factors and that the attentional component in visual field asymmetries must be controlled in order to approximate more closely a true assessment of the relative functional capabilities of the right and left cerebral hemispheres.

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