Authors
Frank Schaeffel, Adrian Glasser, Howard C Howland
Publication date
1988/1/1
Journal
Vision research
Volume
28
Issue
5
Pages
639-657
Publisher
Pergamon
Description
We raised chickens with defocusing lenses of differing powers in front of their eyes. For this purpose, small hoods made from soft, thin leather were carefully fitted to their heads. Lenses were attached to the hoods by velcro fasteners and could be easily removed for cleaning. The powers of the lenses were such that their optical effects could be compensated for by accommodation. It was verified by infrared (IR) photoretinoscopy that the chickens could keep their retinal images in focus. Wearing a lens resulted in a consistent shift of the non cycloplegic refractive state (measured without the lens) which was in the direction to compensate for the lens. We used a sensitive technique (precision= ± 50 μm as estimated from the variability of repeated measurements) to measure the posterior nodal distance (PND) in excised eyes of birds grown with lenses. The PND, in turn, was used to compare eyes treated with different …
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F Schaeffel, A Glasser, HC Howland - Vision research, 1988