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Schaeffel, F., Hagel, G., Eikermann, J. & Collett, T. (1994) Lower-field myopia and astigmatism in amphibians and chickens. Journal of the Optical Society of America A, 11 487–495. 
Added by: Sarina (12 Jul 2009 00:18:13 UTC)   Last edited by: Sarina (12 Jul 2009 00:18:39 UTC)
Resource type: Journal Article
DOI: 10.1364/JOSAA.11.000487
BibTeX citation key: Schaeffel1994
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Categories: Englisch = English
Keywords: Akkommodation = Accommodation, Amphibien = Amphibians
Creators: Collett, Eikermann, Hagel, Schaeffel
Collection: Journal of the Optical Society of America A
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In some afoveate vertebrates refractive state appears to vary over the eye to match the average viewing distances of different areas of the visual field. However, precise measurements are difficult to obtain even in anesthetized animals, because standard methods of refraction are not designed for off-axis measurements and because the presence of astigmatism may fog the results. Therefore we developed a new automated objective technique, automated infrared photoretinoscopy, and measured off-axis refractions in alert chickens and amphibians. We found, in agreement with previous studies, that chickens (Gallus domesticus) are myopic and also have some astigmatism in the lower visual field. Lower-field myopia was, however, variable. It did not match the distance to the ground precisely, but it declined with age (as increased head height would predict). With-the-rule astigmatism was noticed in early posthatching development; it was striking even along the opticaxis. The astigmatism lessened with age, as it does in human infants. Frogs (Rana pipiens and Rana temporaria) displayed pronounced myopic astigmatism that was confined to the lower visual field. Salamanders (Salamandra salamandra) and toads (Bufo bufo) showed less variation in refractive state across the visual field, although toads also were myopic in the lower visual field.
Added by: Sarina  Last edited by: Sarina
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