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Henze, M. J., Schaeffel, F., Wagner, H. .-J. & Ott, M. (2004) Accommodation behaviour during prey capture in the vietnamese leaf turtle ( Geoemyda spengleri). Journal of Comparative Physiology A, 190 139–146. 
Added by: Sarina (16 Dec 2008 20:27:07 UTC)   Last edited by: Sarina (19 Jun 2009 15:33:53 UTC)
Resource type: Journal Article
DOI: 10.1007/s00359-003-0479-y
BibTeX citation key: Henze2004a
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Categories: Englisch = English
Keywords: Akkommodation = Accommodation, Schildkröten = Turtles, Sehvermögen = Visual Perception
Creators: Henze, Ott, Schaeffel, Wagner
Collection: Journal of Comparative Physiology A
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Vietnamese leaf turtles ( Geoemyda spengleri) were tested for their ability to focus on prey objects at various distances. Accommodation was continuously measured by infrared photoretinoscopy. All animals investigated during this study showed a surprisingly high precision of accommodation over a range of over 30 D. Measured accommodation matched the target distance accurately for distances between 3 and 17 cm. The turtles switched between independent and coupled accommodation in the two eyes. Independent accommodation was observed when the turtles inspected their environment visually without a defined object of interest. Coupled accommodation was only observed during binocular prey fixation. When a turtle aimed at a target, the symmetrical focus of both eyes persisted even if vision was totally blocked in one eye or altered by ophthalmic lenses. This suggests that the eyes were linked by internal neuronal mechanisms. The pupil of the eye responded clearly to changes in ambient light intensity. A strong decrease in pupil size was also observed when the eye was focused on a close target. In this case, the constriction of the pupil probably aids in the deformation of the eye lens during near-accommodation.
Added by: Sarina  Last edited by: Sarina
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