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J. C. He; Theoretical Study of Relationship Between Angle Lambda and Wavefront Aberrations in Model Eyes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1565.
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Angle Lambda is an important factor in contributing aberrations in the human eye. High correlation between Zernike higher order aberrations and the offset of the pupil center to the corneal vertex (hence the angle lambda) was found only for coma, but not for other terms, in a group of 103 young subjects (Lu F. et al. J. Optom. 2008). Purpose of this study is to theoretically model the effect of angle lambda on Zernike aberrations in model eyes.
Ray-tracing was performed for four model eyes (Gullstrand-LeGrand; Navarro et al. 1985; Liou-Brennan 1997; Dubbelman et al. 2001, 2002) to calculated wavefront aberrations in the anterior corneal surface and the whole eye using self-developed MatLab program. 36 terms of Zernike aberrations (up to 7th order) were derived with Gram-Schmidt procedures. Angle lambda was varied from 0 to 10 degree.
All Zernike aberrations which are rotationally asymmetrical to the line of sight were zero for every model eyes when angle lambda was at zero, and their levels increase with the angle lambda. Astigmatism and coma were the aberrations with most changes with the angle lambda in both the anterior corneal surface and the whole eye, and with comparable amplitudes between each other. The rest rotationally asymmetrical higher order aberrations had amplitudes less than 20% of those of the astigmatism or coma when angle lambda was not equal to zero.
The results suggest that the angle lambda is the most influential factor for astigmatism and coma, and thus explained why influence of the angle lambda on higher order aberrations can be revealed easily only for coma, but not for other higher order Zernike terms, in population study of human eye aberrations.
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