April 2009
Volume 50, Issue 13
ARVO Annual Meeting Abstract  |   April 2009
Local Effects on Myopic and Astigmatic Eye Growth in Chickens
Author Affiliations & Notes
  • C.-H. Chu
    School of Optometry, Hong Kong Polytechnic University, Hong Kong, China
  • L. Deng
    Department of Vision Science, New England College of Optometry, Boston, Massachusetts
  • C.-S. Kee
    School of Optometry, Hong Kong Polytechnic University, Hong Kong, China
  • Footnotes
    Commercial Relationships  C.-H. Chu, None; L. Deng, None; C.-S. Kee, None.
  • Footnotes
    Support  HKPolyU-CRG G-YG07
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 3933. doi:
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      C.-H. Chu, L. Deng, C.-S. Kee; Local Effects on Myopic and Astigmatic Eye Growth in Chickens. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3933.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : To determine the effects of form depriving full or restricted regions of visual field on myopic and astigmatic eye growth in chickens.

Methods: : Forty-five White Leghorn chicks (Gallus gallus domesticus) were form deprived by translucent diffusers monocularly from day 5 to day 26. The diffusers covered either full ("F", n = 10) or half of the animals’ visual fields (Temporal, "T", n= 9; Nasal, "N", n= 9; Superior, "S", n= 8; Inferior, "I", n= 9). When the chicks were anaesthetized, refractive errors were measured using a modified Hartinger refractometer at baseline and weekly after that for 3 weeks.

Results: : At the end of the 3-wk treatment period, almost all of the partial-field form deprivation produced significantly less amounts of spherical-equivalent ametropia (mean ± SD: F= –14.1 ± 8.2D; T= –3.9 ± 2.3D; N= –2.5 ± 2.8D; S= –0.27 ± 1.5D; I= –6.2 ± 2.8D) and astigmatism (mean ± SD: F= 6.2 ± 4.2D; T= 3.7 ± 2.5D; N= 1.8 ± 1.4D; S= 1.7 ± 1.3D; I= 1.8 ± 1.5D) compared to full-field form deprivation (one-way ANOVA, both p≤0.001, Tukey’s post-hoc pairwise comparisons), the only exception was the astigmatism induced by temporal- and full-field form deprivations.Using a linear mixed-effects model to fit the growth curves of individual refractive components showed that both age and the interaction of age and treatment had significant effects on spherical equivalent, astigmatism, J45 astigmatic component, the most-hyperopic and the most-myopic principal powered meridians (all p< 0.05).

Conclusions: : Form deprivations of full or restricted regions of visual field produced different degrees of ametropia and had significant effect on particular astigmatic component. These results suggest that the susceptibility to optically-induced myopic and astigmatic eye growth varies across the visual field.

Keywords: emmetropization • astigmatism • myopia 

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