| 1. |
- Berry, Richard P., et al.
(author)
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Form vision in the insect dorsal ocelli: An anatomical and optical analysis of the dragonfly median ocellus
- 2007
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 47:10, s. 1394-1409
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Journal article (peer-reviewed)abstract
- Previous work has suggested that dragonfly ocelli are specifically adapted to resolve horizontally extended features of the world, such as the horizon. We investigate the optical and anatomical properties of the median ocellus of Hemicordulia tau and Aeshna mixta to determine the extent to which the findings support this conclusion. Dragonfly median ocelli are shown to possess a number of remarkable properties: astigmatism arising from the elliptical shape of the lens is cancelled by the bilobed shape of the inner lens surface, interference microscopy reveals complex gradients of refractive index within the lens, the morphology of the retina results in zones of high acuity, and the eye has an exceedingly high sensitivity for a diurnal terrestrial invertebrate. It is concluded that dragonfly ocelli employ a number of simple, yet elegant, anatomical and optical strategies to ensure high sensitivity, fast transduction speed, wide fields of views and a modicum of spatial resolving power. (C) 2007 Elsevier Ltd. All rights reserved.
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| 2. |
- Berry, Richard P., et al.
(author)
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Form vision in the insect dorsal ocelli: An anatomical and optical analysis of the Locust Ocelli
- 2007
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 47:10, s. 1382-1393
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Journal article (peer-reviewed)abstract
- The dorsal ocelli are commonly considered to be incapable of form vision, primarily due to underfocused dioptrics. We investigate the extent to which this is true of the ocelli of the locust Locusta migratoria. Locust ocelli contain thick lenses with a pronounced concavity on the inner surface, and a deep clear zone separating retina and lens. In agreement with previous research, locust ocellar lenses were found to be decidedly underfocused with respect to the retina. Nevertheless, the image formed at the level of the retina contains substantial information that may be extractable by individual photoreceptors. Contrary to the classical view it is concluded that some capacity for resolution is present in the locust ocelli.
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| 3. |
- Fagard, Jacqueline, et al.
(author)
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The role of the corpus callosum in the perception of reversible figures in children
- 2008
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In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 48, s. 2451-2455
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Journal article (peer-reviewed)abstract
- To test the role of interhemispheric competition through the corpus callosum in the perceptual alternation of reversible figures, we compared children with callosal pathology and typically developing children on a bistable stimulus task. The children with corpus callosum pathology reported significantly less changes of percepts per minute than the age-matched typically developing children. In addition, older typically developing children reported significantly more changes of percepts than the younger ones. These results support the hypothesis that the rate of reversal between two interpretations of a bistable stimulus may be partly mediated by the corpus callosum.
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| 4. |
- Garm, Anders, et al.
(author)
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Unique structure and optics of the lesser eyes of the box jellyfish Tripedalia cystophora
- 2008
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 48:8, s. 1061-1073
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Journal article (peer-reviewed)abstract
- The visual system of box jellyfish comprises a total of 24 eyes. These are of four types and each probably has a special function. To investigate this hypothesis the morphology and optics of the lesser eyes, the pit and slit eyes, were examined. The pit eyes hold one cell type only and are probably mere light meters. The slit eyes, comprising four cell types, are complex and highly asymmetric. They also hold a lens-like structure, but its optical power is minute. Optical modeling suggests spatial resolution, but only in one plane. These unique and intriguing traits support strong peripheral filtering.
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| 5. |
- Gislén, Anna, et al.
(author)
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The accommodative pupil responses of children and young adults at low and intermediate levels of ambient illumination
- 2008
-
In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 48:8, s. 989-993
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Journal article (peer-reviewed)abstract
- Accommodative pupil constrictions were compared between 27 children (9-10 years) and 13 young adults (22-26 years) in order to clarify the issue whether or not children have such a response. Accommodative stimuli of 4 and 7 diopters were used to elicit the response and experiments were performed at 5 and 100 lux in order to investigate whether the level of ambient light has different effects on developing and mature visual systems. The accommodative pupil response is present in children, but weaker than in adults. Different levels of ambient light lead to only minor additional differences between children and adults. The weaker accommodative pupil response of children may be a consequence of their superior accommodative ranges, which make it unnecessary to close the pupil to increase depth of field. Adults, in contrast, may do better with smaller pupils that reduce accommodative demand because of increased depth of field. A mature human visual system may furthermore be better tuned to handle dimmer and thus noisier images in the photopic range than the developing visual system of a child. (C) 2008 Elsevier Ltd. All rights reserved.
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| 6. |
- Gislén, Anna, et al.
(author)
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Visual training improves underwater vision in children
- 2006
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 46:20, s. 3443-3450
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Journal article (peer-reviewed)abstract
- Children in a tribe of sea-gypsies from South-East Asia have been found to have superior underwater vision compared to European children. In this study, we show that the improved underwater vision of these Moken children is not due to better contrast sensitivity in general. We also show that European children can achieve the same underwater acuity as the Moken children. After I month of underwater training (I I sessions) followed by 4 months with no underwater activities, European children showed improved underwater vision and distinct bursts of pupil constriction. When tested 8 months after the last training session in an outdoor pool in bright sunlight-comparable to light environments in South-East Asia-the children had attained the same underwater acuity as the sea-gypsy children. The achieved performance can be explained by the combined effect of pupil constriction and strong accommodation. (c) 2006 Elsevier Ltd. All rights reserved.
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| 7. |
- Grönqvist, Helena, et al.
(author)
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Developmental asymmetries between horizontal and vertical tracking
- 2006
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In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 46:11, s. 1754-1761
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Journal article (peer-reviewed)abstract
- The development of the asymmetry between horizontal and vertical eye tracking was investigated longitudinally at 5, 7, and 9 months of age. The target moved either on a 2D circular trajectory or on a vertical or horizontal 1D sinusoidal trajectory. Saccades, smooth pursuit, and head movements were measured. Vertical tracking was found to be inferior to horizontal tracking at all age levels. The results also show that the mechanisms responsible for horizontal and vertical tracking mutually influence one another in the production of 2D visual pursuit. Learning effects were observed within-trials but no transfer between trials was found.
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| 8. |
- Johansson, Kjell, et al.
(author)
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Structural changes in the developing retina maintained in vitro.
- 2005
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 45:25-26, s. 3235-3243
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Journal article (peer-reviewed)abstract
- The present study examined the emergence of structural remodeling in explanted neonatal rat retina. Immunohistochemical analysis demonstrated signs of glial and neuronal remodeling after I I days in vitro and included the activation of Muller cells, the formation of ectopic neuropil areas and sprouting of photoreceptor terminals. We also observed that cholinergic and GABA-ergic amacrine cells displayed signs of disorganized laminations. These results demonstrate that retinal culturing initiates structural changes that show morphological similarities to glial and neuronal remodeling identified in retinitis pigmentosa retinas and experimentally detached retinas.
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| 9. |
- Kato, Masaharu, et al.
(author)
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Sensitivity to second-order motion in 10-month-olds
- 2008
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In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 48:10, s. 1187-1195
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Journal article (peer-reviewed)abstract
- Ten-month-old infants' sensitivity to first-order motion (FOM) defined by luminance and second-order motion (SOM) defined by flickering was measured in an eye-tracking paradigm. We used a small single disc or gratings moving horizontally. Although infants could track the SOM of a small disc, they failed to exhibit smooth pursuit eye movements. They also failed to track SOM gratings with smooth pursuit. However, the gain of tracking based on slow eye movement was influenced by the motion direction of SOM in cases when both FOM and SOM were presented simultaneously, suggesting some sensitivity to SOM.
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| 10. |
- Khorramshahi, Omid, et al.
(author)
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A complex system of ligaments and a muscle keep the crystalline lens in place in the eyes of bony fishes (teleosts).
- 2008
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 48:13, s. 1503-1508
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Journal article (peer-reviewed)abstract
- The suspension of the crystalline lens in the eye was studied in 11 species of teleost (bony fish) from 10 families and 7 orders by light and electron microscopy. In all species there were 4-5 ligaments in about the equatorial plane of the eye, in which also the tendon of the retractor lentis muscle attaches to the lens. In two cichlid species two additional ligaments were found running from the mid-posterior surface of the lens to the optic nerve head, where they attach to the falciform process. Lens suspension in teleosts is more complex than previously described and well-suited to firmly keep the heavy spherical lens in position for well-focused vision.
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| 11. |
- Kröger, Ronald, et al.
(author)
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Space-saving advantage of an inverted retina.
- 2009
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 49:18, s. 2318-2321
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Journal article (peer-reviewed)abstract
- Vertebrate eyes are of the simple or camera type with a single optical system that creates an image on the retina in the back of the eye. There, the visual information is encoded as nervous signals by photoreceptors, processed by retinal neurons, and then sent to the brain via the optic nerve. Surprisingly at first sight, the retinal neurons are located between the lens and the light-sensitive parts of the photoreceptors. The tissue scatters some light, which leads to loss of light and image blur. The inverted retina has, therefore, long been regarded as inferior. Here, we provide evidence that the inverted retina actually is a superior space-saving solution, especially in small eyes. The inverted retina has most likely facilitated the evolution of image-forming eyes in vertebrates, and it still benefits especially small and highly visual species.
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| 12. |
- Lind, Olle, et al.
(author)
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Avian colour vision: Effects of variation in receptor sensitivity and noise data on model predictions as compared to behavioural results.
- 2009
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 49, s. 1939-1947
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Journal article (peer-reviewed)abstract
- Colour vision models require measurement of receptor noise and the absorbance of visual pigments, oil droplets, and ocular media. We have studied how variation in these parameters influences colour matching, spectral sensitivity, and colour discrimination predictions in four bird species. While colour match predictions are sensitive to variation in visual pigment and oil droplet absorbance data, discrimination predictions are mostly sensitive to variation in receptor noise. Ocular media transmittance influences only modelled spectral sensitivities at short wavelengths. A comparison between predicted and measured spectral sensitivities in domestic fowl and duck revealed large discrepancies, likely because of influences from achromatic mechanisms.
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| 13. |
- Mönestam, Eva, et al.
(author)
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Associations between subjective and objective visual function in patients with unilateral macular holes
- 2008
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In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 48:1, s. 104-108
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Journal article (peer-reviewed)abstract
- Forty-six patients with uniocular macular holes and unaffected, fellow eyes were studied to evaluate inter- and intraocular associations between various objective tests of visual function and perceived visual ability. The affected eye had significant associations between visual acuity (VA) and the fovea threshold test, but for the fellow eye only VA and low-contrast VA 10% were associated. The reduction in visual acuity under low-contrast conditions relative to high-contrast did not differ between the affected eye and the healthy eye. Subjective visual ability seems to depend more on the visual acuity of the affected eye than the healthy eye.
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| 14. |
- Poom, Leo, et al.
(author)
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Dissociations between slant-contrast and reversed slant-contrast
- 2007
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In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 47:6, s. 746-754
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Journal article (peer-reviewed)abstract
- A vertical test probe is misperceived as slanted in the opposite direction to an inducer when disparity specifies the inducer slant while monocular cues specify a frontoparallel surface (slant-contrast). In reversed cue conditions with vertical axis slant the test probe is misperceived as slanted in the same direction as the inducer (reversed slant-contrast). We found reliable slant-contrast and reversed slant-contrast with inducers having horizontal-axis slant. The reversed slant-contrast was not influenced when the inducer and probe were separated in the frontal plane or in disparity depth whereas slant contrast was degraded, especially in the latter condition. Slant contrast was most pronounced when the inducer was slanted like a ceiling compared to like a ground. No such difference was found for the reversed slant-contrast. When the cue conflict was minimized slant-contrast was reduced, but only with inducers having ground-like slant. Implications for an existing model explaining the slant effects are discussed.
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| 15. |
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| 16. |
- Rosander, Kerstin, et al.
(author)
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Cortical processing of visual motion in young infants
- 2007
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In: Vision Research. - : Elsevier BV. - 0042-6989 .- 1878-5646. ; 47:12, s. 1614-1623
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Journal article (peer-reviewed)abstract
- High-density EEG was used to investigate the cortical processing of a rotatirig visual pattern in 2-, 3-, and 5-month-old infants and in adults. Motion induced ERP in the parietal and the temporal-occipital border regions (OT) was elicited at all ages. The ERP was discernable in the 2-months-olds, significant and unilateral in the 3-month-olds and significantly bilateral in the 5-month-olds and adults. The motion induced ERP in the primary visual area was absent in the 2-month-olds and later than in the OT area for the 3-month-olds indicating that information to OT may be supplied by the VI bypass at these ages. The results are in agreement with behavioural and psychophysical. data in infants.
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| 17. |
- Scholtyssek, Christine, et al.
(author)
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Brightness discrimination in the harbor seal (Phoca vitulina)
- 2008
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 48:1, s. 96-103
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Journal article (peer-reviewed)abstract
- The brightness discrimination ability of a mate harbor seal was investigated at an ambient illumination of 0.9 lx. The visual stimuli consisted of circular gray discs that were presented on a black background on a TFT monitor. Eight standard intensities were tested against sets of lower comparison intensities. In accordance with Weber's law we observed a constant gain of the just noticeable intensity difference with increasing intensity of the standard stimulus. The calculated Weber fraction is 0.14. This result indicates that the brightness discrimination ability of the harbor seal is comparable to that of humans.
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| 18. |
- Theobald, Jamie, et al.
(author)
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Visual summation in night-flying sweat bees: A theoretical study
- 2006
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In: Vision Research. - : Elsevier BV. - 1878-5646 .- 0042-6989. ; 46:14, s. 2298-2309
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Journal article (peer-reviewed)abstract
- Bees are predominantly diurnal; only a few groups fly at night. An evolutionary limitation that bees must overcome to inhabit dim environments is their eye type: bees possess apposition compound eyes, which are poorly suited to vision in dim light. Here, we theoretically examine how nocturnal bees Megalopta genalis fly at light levels usually reserved for insects bearing more sensitive superposition eyes. We find that neural summation should greatly increase M. genalis's visual reliability. Predicted spatial summation closely matches the morphology of laminal neurons believed to mediate such summation. Improved reliability costs acuity, but dark adapted bees already suffer optical blurring, and summation further degrades vision only slightly. (c) 2006 Elsevier Ltd. All rights reserved.
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| 19. |
- Nilsson, Josefin, 1973, et al.
(author)
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Rod a-wave analysis using high intensity flashes adds information on rod system function in 25% of clinical ERG recordings.
- 2008
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In: Vision research. - : Elsevier BV. - 0042-6989. ; 48:18, s. 1920-5
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Journal article (peer-reviewed)abstract
- PURPOSE: To investigate whether rod a-wave analysis using high intensity flashes adds information above that obtained with standard ERG. METHODS: A total of 2,396 eyes were recorded. Patient age was 2.4 months-84.6 years. RESULTS: A-wave analysis of high intensity flashes provided additional information on rod system function in 25% of eyes recorded, most importantly in subjects with midretinal disease and artificially reduced rod responses. High intensity flashes also provided measurable responses for longitudinal monitoring in rod dystrophies with non-recordable rod ERGs. CONCLUSIONS: Clinical ERG testing would benefit greatly from adding high intensity flashes to its standard testing conditions.
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| 20. |
- Popovic, Zoran, 1966, et al.
(author)
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The relation between resolution measurements and numbers of retinal ganglion cells in the same human subjects
- 2005
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In: Vision Research. - : Elsevier BV. - 0042-6989. ; 45:17, s. 2331-2338
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Journal article (peer-reviewed)abstract
- Limiting factors of resolution have previously only been investigated by using resolution data and retinal ganglion cell spacing data from different individuals. We report on our unique opportunity to study the intra-individual relationship in three human subjects between retinal ganglion cell separations and resolution thresholds, measured with high-pass resolution perimetry. Our data show that resolution is directly proportional to half the midget population, in accordance with the hypothesis that a dichotomous midget ON/OFF population mediates resolution. (c) 2005 Elsevier Ltd. All rights reserved.
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