A detailed paraxial schematic eye for the White Leghorn chick |
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Authors: | Natalia V Avila Sally A McFadden |
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Institution: | (1) School of Psychology, Faculty of Science and Information Technology, The University of Newcastle, Newcastle, NSW, 2308, Australia |
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Abstract: | We studied the normal ocular development of the chick (Gallus gallus domesticus, White Leghorn) up to 15 days of age using both longitudinal and cross-sectional methods. The change in refractive error,
corneal curvature and axial ocular distances were used to construct schematic eyes. Equations are presented which allow prediction
of refractive error changes associated with changes in vitreous chamber depth. The mean refractive error was +3.2 D at hatching,
which reduced by 66% over the first 3 days and stabilized by 11 days of age. The lens thickened and the anterior chamber deepened
from hatching, but vitreal elongation and corneal flattening were delayed until after the first 3 days, suggesting that normal
eye growth may be initially inhibited or inactive during an initial emmetropization period, and subsequently activated in
response to myopic defocus arising from the continually expanding lens. Finally, when compared with published data on other
chick strains, we find differences in the degree of hyperopia at hatching due to differences in lens thickness. However, the
rate of ocular and vitreal expansion and the developmental changes in corneal power are similar, making the schematic eyes
presented here generally applicable to different strains of chickens. |
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