Lower-field myopia and astigmatism in amphibians and chickens

Schaeffel, Frank; Hagel, Gabi; Eikermann, Judith; Collett, Thomas S

doi:10.1364/josaa.11.000487

Cited by 73 publications

(46 citation statements)

References 15 publications

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“…39 Studies in amphibians have shown that fluctuations in astigmatism, correlated with changes of the refractive power along the vertical meridian, are particularly prevalent in the ventral visual field. 40,41 The mechanism underpinning astigmatism in the ventral field is not understood, although astigmatism is induced by the corneal surface, in which the curvature tends to decrease from dorsal to ventral aspects. VAX2 also plays an important role in controlling retinoic acid (RA) metabolism in the developing eye in vertebrates, particularly in maturation of the retina, 42 but RA is also involved in development of the cornea.…”

Section: Discussionmentioning

confidence: 99%

Identification of a Candidate Gene for Astigmatism

Lopes

Hysi

Verhoeven

et al. 2013

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. Astigmatism is a common refractive error that reduces vision, where the curvature and refractive power of the cornea in one meridian are less than those of the perpendicular axis. It is a complex trait likely to be influenced by both genetic and environmental factors. Twin studies of astigmatism have found approximately 60% of phenotypic variance is explained by genetic factors. This study aimed to identify susceptibility loci for astigmatism. METHODS.We performed a meta-analysis of seven genome-wide association studies that included 22,100 individuals of European descent, where astigmatism was defined as the number of diopters of cylinder prescription, using fixed effect inverse variance-weighted methods. RESULTS.A susceptibility locus was identified with lead single nucleotide polymorphism rs3771395 on chromosome 2p13.3 (meta-analysis, P ¼ 1.97 3 10 À7 ) in the VAX2 gene. VAX2 plays an important role in the development of the dorsoventral axis of the eye. Animal studies have shown a gradient in astigmatism along the vertical plane, with corresponding changes in refraction, particularly in the ventral field.CONCLUSIONS. This finding advances the understanding of refractive error, and provides new potential pathways to be evaluated with regard to the development of astigmatism. (Invest Ophthalmol Vis Sci. 2013;54:1260-1267) DOI: 10.1167/iovs.12-10463 A stigmatism is a common refractive error that reduces vision, where the curvature and refractive power of the cornea in one meridian are less than those of the perpendicular axis. There are two components of astigmatism that can be independently measured, refractive astigmatism (also called noncorneal astigmatism) and corneal astigmatism; this study deals with refractive astigmatism. Astigmatism is an important clinical problem because it is common; prevalence ranges between 20% and 29.3% among adults in Europe and 36.2% among subjects 20 years old and older in the United States, [1][2][3] From the

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Section: Discussionmentioning

confidence: 99%

Identification of a Candidate Gene for Astigmatism

Lopes

Hysi

Verhoeven

et al. 2013

Invest. Ophthalmol. Vis. Sci.

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“…The animals were mounted into a stereotactic apparatus and the eyes were focused on the stimulus screen (24 inch LCD monitor, gamma corrected, Belineao.display 4.1, Belinea; refresh rate, 70 Hz)-placed 50 cm in front of the animals' eyes-by using PMM contact lenses (Soflex Israelens Contact Lenses Ltd.) and an infrared video refractor (Schaeffel et al, 1994;Troilo et al, 2007). The stimulus screen spanned 55°horizontal ϫ 37.5°vertical of the animal's central field of view.…”

Section: Methodsmentioning

confidence: 99%

Color Blobs in Cortical Areas V1 and V2 of the New World Monkey Callithrix jacchus, Revealed by Non-Differential Optical Imaging

Salzmann¹,

Bartels²,

Logothetis³

et al. 2012

Journal of Neuroscience

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Color vision is reserved to only few mammals, such as Old World monkeys and humans. Most Old World monkeys are trichromats. Among them, macaques were shown to exhibit functional domains of color-selectivity, in areas V1 and V2 of the visual cortex. Such color domains have not yet been shown in New World monkeys. In marmosets a sex-linked dichotomy results in dichromatic and trichromatic genotypes, rendering most male marmosets color-blind. Here we used trichromatic female marmosets to examine the intrinsic signal response in V1 and V2 to chromatic and achromatic stimuli, using optical imaging. To activate the subsystems individually, we used spatially homogeneous isoluminant color opponent (red/green, blue/yellow) and hue versus achromatic flicker (red/gray, green/gray, blue/gray, yellow/gray), as well as achromatic luminance flicker. In contrast to previous optical imaging studies in marmosets, we find clearly segregated color domains, similar to those seen in macaques. Red/green and red/gray flicker were found to be the appropriate stimulus for revealing color domains in single-condition maps. Blue/gray and blue/yellow flicker stimuli resulted in faint patch-patterns. A recently described multimodal vessel mapping approach allowed for an accurate alignment of the functional and anatomical datasets. Color domains were tightly colocalized with cytochrome oxidase blobs in V1 and with thin stripes in V2. Thus, our findings are in accord with 2-Deoxy-D-glucose studies performed in V1 of macaques and studies on color representation in V2. Our results suggest a similar organization of early cortical color processing in trichromats of both Old World and New World monkeys.

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“…Maintenance of constant velocity is likely to facilitate accurate path planning and robustly stable running in uneven terrain. Birds also have lower-field myopia (near-sightedness), allowing them to keep the ground in focus at eye height with the upper field focused at distances (Hodos and Erichsen, 1990;Schaeffel et al, 1994), enhancing their ability to dynamically gauge terrain. The results of the present study suggest that birds use visual route planning when presented with sufficient visual information.…”

Section: The Role Of Vision In Route Planning For Obstacle Negotiationmentioning

confidence: 99%

Birds achieve high robustness in uneven terrain through active control of landing conditions

Birn-Jeffery

Daley

2012

Journal of Experimental Biology

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SUMMARYWe understand little about how animals adjust locomotor behaviour to negotiate uneven terrain. The mechanical demands and constraints of such behaviours likely differ from uniform terrain locomotion. Here we investigated how common pheasants negotiate visible obstacles with heights from 10 to 50% of leg length. Our goal was to determine the neuro-mechanical strategies used to achieve robust stability, and address whether strategies vary with obstacle height. We found that control of landing conditions was crucial for minimising fluctuations in stance leg loading and work in uneven terrain. Variation in touchdown leg angle ( TD ) was correlated with the orientation of ground force during stance, and the angle between the leg and body velocity vector at touchdown ( TD ) was correlated with net limb work. Pheasants actively targeted obstacles to control body velocity and leg posture at touchdown to achieve nearly steady dynamics on the obstacle step. In the approach step to an obstacle, the birds produced net positive limb work to launch themselves upward. On the obstacle, body dynamics were similar to uniform terrain. Pheasants also increased swing leg retraction velocity during obstacle negotiation, which we suggest is an active strategy to minimise fluctuations in peak force and leg posture in uneven terrain. Thus, pheasants appear to achieve robustly stable locomotion through a combination of path planning using visual feedback and active adjustment of leg swing dynamics to control landing conditions. We suggest that strategies for robust stability are context specific, depending on the quality of sensory feedback available, especially visual input.

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Lower-field myopia and astigmatism in amphibians and chickens

Cited by 73 publications

References 15 publications

Identification of a Candidate Gene for Astigmatism

Identification of a Candidate Gene for Astigmatism

Color Blobs in Cortical Areas V1 and V2 of the New World Monkey Callithrix jacchus, Revealed by Non-Differential Optical Imaging

Birds achieve high robustness in uneven terrain through active control of landing conditions

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