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R. Ramamirtham, L.-F. Hung, Y. Qiao-Grider, J. Huang, E. L. Smith, III; Characteristics of Corneal and Internal Wave Aberrations in Rhesus Monkeys. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1035.
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In adult humans and adolescent monkeys high-order monochromatic wave aberrations produced by the anterior corneal surface are partially counterbalanced by aberrations produced by the internal optics of the eye. However, little is known about the relative balance between internal and external ocular components early in life when the eye exhibits higher amount of wave aberrations and undergoes rapid shape and organizational changes. The purpose of this study was to characterize the wave aberrations associated with the anterior corneal surface and the internal optics in normal infant monkey eyes during emmetropization.
Cross-sectional data were obtained from 35 infant (ages 25 ± 7 days) and 6 adolescent monkeys (ages 2-5 years). Longitudinal data were obtained from 5 of 35 infants every 2-4 weeks until about 300 days of age. The aberrations for the whole eye were obtained using a Shack-Hartmann wavefront sensor aligned with the line of sight. The aberrations for the anterior cornea and the eye’s internal optics were derived from photokeratoscope elevation data and subtraction of Zernike coefficients for the cornea from their corresponding coefficients for the whole eye, respectively.
During early emmetropization, the high-order total RMS errors for the anterior cornea and the eye’s internal optics decreased and reached adolescent-like values by about 150 days of age with the 3rd order terms for trefoil and coma showing the greatest changes. Positive spherical aberration due to the anterior cornea, which was only partially counterbalanced at 3 weeks of age by the negative spherical aberration due to the eye’s internal optics, was relatively constant during emmetropization. However, with time the spherical aberration for the internal components changed, sometimes increasing in magnitude, to counterbalance the spherical aberration from the anterior cornea, reducing the total amount of spherical aberration for the whole eye.
Compared to adolescent monkeys, infants exhibit a less precise balance between the aberrations associated with the anterior cornea and the eye’s internal optics. The decrease in the high-order aberrations for the whole eye early in life is due to a decrease in high-order aberrations, particularly for 3rd order aberrations, from both the anterior corneal surface and the eye’s internal optics, and the development of a more precise balance of aberrations between the eye’s individual optical components, especially for spherical aberration.
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