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F. Lu, J. Wu, Y. Shen, Q. Wang, Q. Yi, J. Qu, J. He; Lateral Coma in the Human Eye is Not Necessarily Determined by Misalignment Between the Line of Sight and the Optic Axis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2791.
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© ARVO (1962-2015); The Authors (2016-present)
To study lateral coma in eyes with minimal misalignment between the line of sight and the optic axis by examining the lateral comas in both the anterior cornea and the whole eye.
Wavefront aberrations in both the anterior cornea and the whole eye were measured for 221 young emmetropic and myopic subjects using a corneal topography system (ATLAS, Carl Zeiss Meditec) and a Hartmann-Shack aberrometer (WASCO, Carl Zeiss Meditec). Lateral comas in both the anterior cornea and the whole eye were derived from the measurements of wavefront aberrations. The lateral coma in the interior optics of the eye was obtained by subtracting corneal coma from the coma of the whole eye. Estimates of the pupil center, corneal vertex and corneal apex were obtained from the ATLAS measurements. Misalignment between the line of sight and the optic axis was estimated from lateral shifts of the pupil center from both the corneal apex and the corneal vertex.
Among the 442 eyes of the subjects, 21 right eyes and 22 left eyes were found to have lateral shifts of the pupil center from both the corneal vertex and the corneal apex of less than 0.01 mm, thus with minimum misalignment between the line of sight and the optic axis. For the 43 eyes with minimum misalignments, mean lateral comas were -0.118±0.070 (OD) and 0.119±0.089 µm (OS) in the anterior cornea and -0.050±0.075 (OD) and 0.017±0.074 µm (OS) in the whole eye. The lateral comas in the internal optics of the eye were 0.068±0.069 in the right eye and -0.103±0.079 in the left eye. The differences in lateral coma between the right and left eyes were significant for the anterior cornea (t=9.72, p<0.0001), the whole eye (t=2.91, p<0.005) and the internal optics (t = 7.58, p<0.0001).
The results indicate that lateral coma does not necessarily depend on misalignment between the line of sight and the optic axis in either the anterior cornea or the whole eye of the human eye. The anterior corneal surface is not rotationally symmetrical to the optic axis.
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