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  • Accommodation  (3)
  • Chickens  (1)
  • (Human plasma)
  • Springer  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 168 (1991), S. 299-303 
    ISSN: 1432-1351
    Keywords: Photorefraction ; Accommodation ; Tytonidae ; Near vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In an examination of the focusing abilities of 15 species of owls, the North American barn owl, Tyto alba pratincola (Bonaparte 1838), was an outstanding accommodator, having a range of accommodation exceeding 10 diopters (Murphy and Howland 1983). Using comparable methods, we examined the accommodation of 4 specimens of the Australian barn owl, Tyto alba delicatula (Gould 1837). We failed to elicit accommodation greater than two diopters, and most stimuli failed to evoke any discernable accommodation at all. Furthermore, examination of other Australian tytonid owls, the grass owl, T. longimembris, the sooty owl, T. tenebricosa, and both the mainland and Tasmanian subspecies of the masked owl, T. novaehollandiae novaehollandiae and T. novaehollandiae castanops, also failed to reveal anything but very moderate accommodative ranges. We conclude that the outstanding accommodative ability of the American barn owl is truly an exception to the modest accommodative abilities of the tytonid owls generally.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 178 (1996), S. 551-561 
    ISSN: 1432-1351
    Keywords: Chickens ; Emmetropization ; Breed ; Gender ; Form deprivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study investigated the influences of breed and gender on the response to form deprivation and subsequent changes (recovery) when normal vision was restored. Two breeds of chickens, the White Leghorn and broiler cross, were compared, as well as male and female chicks for the White Leghorn breed. Normal eye growth was faster in the more rapidly growing broiler chicks; gender-differences were not as great as breed-differences although male White Leghorns ultimately became heavier and showed slightly greater normal eye growth than females. While both breeds showed high myopia and axial elongation in response to form deprivation, they differed significantly in the magnitude of their response, with White Leghorns showing more myopia and greater axial elongation and also recovering more slowly. Responses to form deprivation were similar for both genders, with respect to both the amount of myopia and axial elongation produced, although the female chicks recovered faster. Together these observations indicate that, although the overall pattern of response of form deprivation is consistent across both breed and gender, related quantitative differences in responses can be expected and need to be taken into account in experimental design and cross-study comparisons.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 170 (1992), S. 263-266 
    ISSN: 1432-1351
    Keywords: Tuatara ; Sphenodon punctatus ; Accommodation ; Photorefraction ; Corneal curvature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Photorefraction and photokeratometry were performed on two juvenile tuatara (Sphenodon punctatus, 7 years of age, total length approx. 27 cm). Sphenodon is the only surviving genus of the Rhynchocephalia, an order of reptiles. Both existing species are endangered and are found only in New Zealand. Even though Walls (1942) has stated that the ciliary muscle is relatively weak in tuataras, we observed 8 D of accommodation. The eyes were found to focus independently and we could induce an anisometropia of 6 D. The average corneal power of the tuatara was found to be 101 D.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 170 (1992), S. 687-689 
    ISSN: 1432-1351
    Keywords: Brown kiwi ; Apteryx australis ; Accommodation ; Photorefraction ; Corneal curvature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Brown kiwis are an endangered species of nocturnal, flightless birds which are native to New Zealand. The resting focus of two specimens has previously been studied by retinoscopy in a zoo while the birds were restrained by their keeper (Sivak and Howland 1987). Those birds appeared to be hyperopic (farsighted) by 2–7 D. In this study, examination with infrared photorefraction of the focusing of two unrestrained, feeding birds showed that they could focus objects at infinity and objects in their immediate environment and that they had modest powers of accommodation. Measurements on two 6 month old kiwi chicks showed their corneal radius of curvature to be between 2.90 and 3.00 mm (117 D and 101 D in power).
    Type of Medium: Electronic Resource
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