Abstract

A growing number of research laboratories are using the new technologies of videokeratoscopy and Shack–Hartmann aberrometry, in combination, to study the optical structure of the human eye. A potential source of error arises, however, because the two instruments are designed to measure the human eye along different reference axes. The Shack–Hartmann aberrometer is usually aligned coaxially with the line of sight, but videokeratoscopes usually are not. Thus far, corneal optics research has not adequately addressed the problem of videokeratoscope–line-of-sight misalignment and its effect on the computation of corneal and internal ocular aberrations. We measured corneal, ocular, and internal aberrations for three normal human eyes, developed a method to compensate for videokeratoscope–line-of-sight misalignment, and analyzed the importance of compensating for the misalignment. Our results show that when the value of angle lambda (the angle between the line of sight and the pupillary axis) is larger than 2°–3°, the misalignment, if ignored, can lead to incorrect estimates of corneal and internal aberrations as well as the corneal/internal aberration balance.

© 2002 Optical Society of America

Full Article  |  PDF Article

Errata

Thomas O. Salmon and Larry N. Thibos, "Videokeratoscope–line-of-sight misalignment and its effect on measurements of corneal and internal ocular aberrations," J. Opt. Soc. Am. A 20, 195-195 (2003)
https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-20-1-195

References

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    [PubMed]
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    [PubMed]
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  45. E. Gudmundsdottir, F. Jonasson, E. Stefansson, H. Sasaki, K. Sasaki, “Corneal and total astigmatism by age. Does the lens compensate for corneal astigmatism? Reykjavik eye study,” Invest. Ophthalmol. Visual Sci. 41, S303 (2000).
  46. T. Oshika, S. Klyce, R. Applegate, H. Howland, “Changes in corneal wavefront aberrations with aging,” Invest. Ophthalmol. Visual Sci. 40, 1351–1355 (1999).
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2001

P. Artal, A. Guirao, E. Berrio, D. Williams, “Compensation of corneal aberrations by the internal optics in the human eye,” J. Vision 1, 1–8 (2001).
[CrossRef]

2000

M. Berrio, A. Guirao, M. Redondo, P. Piers, P. Artal, “The contribution of the cornea and internal ocular surfaces to the changes in the aberrations of the eye with age,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

J. He, E. Ong, J. Gwiazda, R. Held, F. Thorn, “Wave-front aberrations in the cornea and the whole eye,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

L. Thibos, “Principles of Hartmann–Shack aberrometry,” J. Refract. Surg. 16, S563–S565 (2000).
[PubMed]

E. Gudmundsdottir, F. Jonasson, E. Stefansson, H. Sasaki, K. Sasaki, “Corneal and total astigmatism by age. Does the lens compensate for corneal astigmatism? Reykjavik eye study,” Invest. Ophthalmol. Visual Sci. 41, S303 (2000).

A. Guirao, P. Artal, “Corneal wave aberration from videokeratoscopy: accuracy and limitations of the procedure,” J. Opt. Soc. Am. A 17, 955–965 (2000).
[CrossRef]

E. Moreno-Barriuso, R. Navarro, “Laser ray tracing versus Hartmann–Shack sensor for measuring optical aberrations in the human eye,” J. Opt. Soc. Am. A 17, 974–985 (2000).
[CrossRef]

P. Prieto, F. Vargas-Martin, S. Goelz, P. Artal, “Analysis of the performance of the Hartmann–Shack sensor in the human eye,” J. Opt. Soc. Am. A 17, 1388–1398 (2000).
[CrossRef]

A. Guirao, M. Redondo, P. Artal, “Optical aberrations of the human cornea as a function of age,” J. Opt. Soc. Am. A 17, 1697–1702 (2000).
[CrossRef]

1999

T. Oshika, S. Klyce, R. Applegate, H. Howland, “Changes in corneal wavefront aberrations with aging,” Invest. Ophthalmol. Visual Sci. 40, 1351–1355 (1999).

T. Oshika, S. D. Klyce, R. A. Applegate, H. C. Howland, M. A. ElDanasoury, “Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis,” Am. J. Ophthalmol. 127, 1–7 (1999).
[CrossRef] [PubMed]

L. Thibos, X. Hong, “Clinical application of the Shack–Hartmann aberrometer,” Optom. Vision Sci. 76, 817–825 (1999).
[CrossRef]

G. Hilmantel, R. Blunt, B. Garret, H. Howland, R. Applegate, “Accuracy of the Tomey topographic modeling system in measuring surface elevations of asymmetric objects,” Optom. Vision Sci. 76, 108–114 (1999).
[CrossRef]

1998

C. Martinez, R. Applegate, S. Klyce, M. McDonald, J. Medina, H. Howland, “Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy,” Arch. Ophthalmol. 116, 1053–1062 (1998).
[CrossRef] [PubMed]

D. Horner, T. Salmon, “Accuracy of the EyeSys 2000 in measuring surface elevation of calibrated aspheres,” Int. Contact Lens Clin. 25, 171–177 (1998).
[CrossRef]

T. Salmon, L. Thibos, “Relative contribution of the cornea and internal optics to the aberrations of the eye,” Optom. Vision Sci. 75(12s), 235 (1998).

P. Artal, A. Guirao, “Contribution of the cornea and lens to the aberrations of the human eye,” Opt. Lett. 23, 1713–1715 (1998).
[CrossRef]

T. Salmon, L. Thibos, “Comparison of the eye’s wave-front aberration measured psychophysically and with the Shack–Hartmann wave-front sensor,” J. Opt. Soc. Am. A 15, 2457–2465 (1998).
[CrossRef]

S. Klein, “Optimal corneal ablation for eyes with arbitrary Hartmann–Shack aberrations,” J. Opt. Soc. Am. A 15, 2580–2588 (1998).
[CrossRef]

1997

J. Liang, D. R. Williams, “Aberrations and retinal image quality of the normal human eye,” J. Opt. Soc. Am. A 14, 2873–2883 (1997).
[CrossRef]

J. Liang, D. R. Williams, D. T. Miller, “Supernormal vision and high-resolution retinal imaging through adaptive optics,” J. Opt. Soc. Am. A 14, 2884–2892 (1997).
[CrossRef]

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

L. N. Thibos, Y. Ming, X. Zhang, A. Bradley, “Spherical aberration of the reduced schematic eye with elliptical refracting surface,” Optom. Vision Sci. 74, 548–565 (1997).
[CrossRef]

L. Thibos, W. Wheeler, D. Horner, “Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error,” Optom. Vision Sci. 74, 367–375 (1997).
[CrossRef]

1996

J. Greivenkamp, M. Mellinger, R. Snyder, J. Schwiegerling, A. Lowman, J. Miller, “Comparison of three videokeratoscopes in measurement of toric test surfaces,” J. Refract. Surg. 12, 229–239 (1996).
[PubMed]

1995

R. Applegate, R. Nunez, J. Buettner, H. Howland, “How accurately can videokeratographic systems measure surface elevation?” Optom. Vision Sci. 72, 785–792 (1995).
[CrossRef]

W. A. Douthwaite, “EyeSys corneal topography measurement applied to calibrated ellipsoidal convex surfaces,” Br. J. Ophthamol. 79, 797–801 (1995).
[CrossRef]

K. L. Cohen, N. K. Tripoli, D. E. Holmgren, J. M. Coggins, “Assessment of the power and height of radial aspheres reported by a computer-assisted keratoscope,” Am. J. Ophthalmol. 119, 723–732 (1995).
[PubMed]

R. Mandell, C. Chiang, S. Klein, “Location of the major corneal reference points,” Optom. Vision Sci. 72, 776–784 (1995).
[CrossRef]

R. Mandell, “Locating the corneal sighting center from videokeratography,” J. Refract. Surg. 11, 253–259 (1995).
[PubMed]

1994

1993

A. Tomlinson, R. Hemenger, R. Garriott, “Method for estimating the spherical aberration of the human crystalline lens in vivo,” Invest. Ophthalmol. Visual Sci. 34, 621–629 (1993).

1992

R. B. Mandell, “The enigma of the corneal contour,” Contact Lens Assoc. Opthalmol. J. 18, 267–273 (1992).

L. Thibos, “The chromatic eye: a new reduced-eye model of ocular chromatic aberration in humans,” Appl. Opt. 31, 3594–3600 (1992).
[CrossRef] [PubMed]

K. Zadnik, D. Mutti, A. Adams, “The repeatability of measurements of the ocular components,” Invest. Ophthalmol. Visual Sci. 33, 2325–2333 (1992).

1979

M. Millodot, J. Sivak, “Contribution of the cornea and lens to the spherical aberration of the eye,” Vision Res. 19, 685–687 (1979).
[CrossRef] [PubMed]

1973

1801

T. Young, “On the mechanism of the eye,” Philos. Trans. R. Soc. London 19, 23–88 (1801).
[CrossRef]

Adams, A.

K. Zadnik, D. Mutti, A. Adams, “The repeatability of measurements of the ocular components,” Invest. Ophthalmol. Visual Sci. 33, 2325–2333 (1992).

Applegate, R.

G. Hilmantel, R. Blunt, B. Garret, H. Howland, R. Applegate, “Accuracy of the Tomey topographic modeling system in measuring surface elevations of asymmetric objects,” Optom. Vision Sci. 76, 108–114 (1999).
[CrossRef]

T. Oshika, S. Klyce, R. Applegate, H. Howland, “Changes in corneal wavefront aberrations with aging,” Invest. Ophthalmol. Visual Sci. 40, 1351–1355 (1999).

C. Martinez, R. Applegate, S. Klyce, M. McDonald, J. Medina, H. Howland, “Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy,” Arch. Ophthalmol. 116, 1053–1062 (1998).
[CrossRef] [PubMed]

R. Applegate, R. Nunez, J. Buettner, H. Howland, “How accurately can videokeratographic systems measure surface elevation?” Optom. Vision Sci. 72, 785–792 (1995).
[CrossRef]

L. Thibos, R. Applegate, J. Schwiegerling, R. Webb, and VSIA Standards Taskforce Members, “Standards for reporting the optical aberrations of the eye,” in Vision Science and Its Applications, V. Lakshminarayanan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 2000), pp. 232–244.

H. Howland, J. Buettner, R. Applegate, “Computation of the shapes of normal corneas and their monochromatic aberrations from videokeratometric measurements,” in Vision Science and Its Applications, Vol. 2 of 1994 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1994), pp. 54–57.

R. Applegate, L. Thibos, A. Bradley, S. Marcos, A. Roorda, T. Salmon, D. Atchison, “Reference axis selection: a subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye,” in Vision Science and Its Applications, V. Lakshminaranayan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington D.C., 2000), pp. 147–149.

Applegate, R. A.

T. Oshika, S. D. Klyce, R. A. Applegate, H. C. Howland, M. A. ElDanasoury, “Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis,” Am. J. Ophthalmol. 127, 1–7 (1999).
[CrossRef] [PubMed]

Artal, P.

Atchison, D.

R. Applegate, L. Thibos, A. Bradley, S. Marcos, A. Roorda, T. Salmon, D. Atchison, “Reference axis selection: a subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye,” in Vision Science and Its Applications, V. Lakshminaranayan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington D.C., 2000), pp. 147–149.

Berny, F.

Berrio, E.

P. Artal, A. Guirao, E. Berrio, D. Williams, “Compensation of corneal aberrations by the internal optics in the human eye,” J. Vision 1, 1–8 (2001).
[CrossRef]

Berrio, M.

M. Berrio, A. Guirao, M. Redondo, P. Piers, P. Artal, “The contribution of the cornea and internal ocular surfaces to the changes in the aberrations of the eye with age,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

Bille, J. F.

Blunt, R.

G. Hilmantel, R. Blunt, B. Garret, H. Howland, R. Applegate, “Accuracy of the Tomey topographic modeling system in measuring surface elevations of asymmetric objects,” Optom. Vision Sci. 76, 108–114 (1999).
[CrossRef]

Bradley, A.

L. N. Thibos, Y. Ming, X. Zhang, A. Bradley, “Spherical aberration of the reduced schematic eye with elliptical refracting surface,” Optom. Vision Sci. 74, 548–565 (1997).
[CrossRef]

R. Applegate, L. Thibos, A. Bradley, S. Marcos, A. Roorda, T. Salmon, D. Atchison, “Reference axis selection: a subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye,” in Vision Science and Its Applications, V. Lakshminaranayan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington D.C., 2000), pp. 147–149.

Buettner, J.

R. Applegate, R. Nunez, J. Buettner, H. Howland, “How accurately can videokeratographic systems measure surface elevation?” Optom. Vision Sci. 72, 785–792 (1995).
[CrossRef]

H. Howland, J. Buettner, R. Applegate, “Computation of the shapes of normal corneas and their monochromatic aberrations from videokeratometric measurements,” in Vision Science and Its Applications, Vol. 2 of 1994 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1994), pp. 54–57.

Chiang, C.

R. Mandell, C. Chiang, S. Klein, “Location of the major corneal reference points,” Optom. Vision Sci. 72, 776–784 (1995).
[CrossRef]

Coggins, J. M.

K. L. Cohen, N. K. Tripoli, D. E. Holmgren, J. M. Coggins, “Assessment of the power and height of radial aspheres reported by a computer-assisted keratoscope,” Am. J. Ophthalmol. 119, 723–732 (1995).
[PubMed]

Cohen, K. L.

K. L. Cohen, N. K. Tripoli, D. E. Holmgren, J. M. Coggins, “Assessment of the power and height of radial aspheres reported by a computer-assisted keratoscope,” Am. J. Ophthalmol. 119, 723–732 (1995).
[PubMed]

Corbett, M.

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

Douthwaite, W. A.

W. A. Douthwaite, “EyeSys corneal topography measurement applied to calibrated ellipsoidal convex surfaces,” Br. J. Ophthamol. 79, 797–801 (1995).
[CrossRef]

El Hage, S.

ElDanasoury, M. A.

T. Oshika, S. D. Klyce, R. A. Applegate, H. C. Howland, M. A. ElDanasoury, “Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis,” Am. J. Ophthalmol. 127, 1–7 (1999).
[CrossRef] [PubMed]

Garret, B.

G. Hilmantel, R. Blunt, B. Garret, H. Howland, R. Applegate, “Accuracy of the Tomey topographic modeling system in measuring surface elevations of asymmetric objects,” Optom. Vision Sci. 76, 108–114 (1999).
[CrossRef]

Garriott, R.

A. Tomlinson, R. Hemenger, R. Garriott, “Method for estimating the spherical aberration of the human crystalline lens in vivo,” Invest. Ophthalmol. Visual Sci. 34, 621–629 (1993).

Goelz, S.

Greivenkamp, J.

J. Greivenkamp, M. Mellinger, R. Snyder, J. Schwiegerling, A. Lowman, J. Miller, “Comparison of three videokeratoscopes in measurement of toric test surfaces,” J. Refract. Surg. 12, 229–239 (1996).
[PubMed]

Grimm, B.

Gudmundsdottir, E.

E. Gudmundsdottir, F. Jonasson, E. Stefansson, H. Sasaki, K. Sasaki, “Corneal and total astigmatism by age. Does the lens compensate for corneal astigmatism? Reykjavik eye study,” Invest. Ophthalmol. Visual Sci. 41, S303 (2000).

Guirao, A.

P. Artal, A. Guirao, E. Berrio, D. Williams, “Compensation of corneal aberrations by the internal optics in the human eye,” J. Vision 1, 1–8 (2001).
[CrossRef]

A. Guirao, M. Redondo, P. Artal, “Optical aberrations of the human cornea as a function of age,” J. Opt. Soc. Am. A 17, 1697–1702 (2000).
[CrossRef]

M. Berrio, A. Guirao, M. Redondo, P. Piers, P. Artal, “The contribution of the cornea and internal ocular surfaces to the changes in the aberrations of the eye with age,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

A. Guirao, P. Artal, “Corneal wave aberration from videokeratoscopy: accuracy and limitations of the procedure,” J. Opt. Soc. Am. A 17, 955–965 (2000).
[CrossRef]

P. Artal, A. Guirao, “Contribution of the cornea and lens to the aberrations of the human eye,” Opt. Lett. 23, 1713–1715 (1998).
[CrossRef]

Gwiazda, J.

J. He, E. Ong, J. Gwiazda, R. Held, F. Thorn, “Wave-front aberrations in the cornea and the whole eye,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

He, J.

J. He, E. Ong, J. Gwiazda, R. Held, F. Thorn, “Wave-front aberrations in the cornea and the whole eye,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

Held, R.

J. He, E. Ong, J. Gwiazda, R. Held, F. Thorn, “Wave-front aberrations in the cornea and the whole eye,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

Hemenger, R.

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

R. Hemenger, A. Tomlinson, K. Oliver, “Corneal optics from videokeratographs,” Ophthalmic Physiol. Opt. 15, 63–68 (1994).
[CrossRef]

A. Tomlinson, R. Hemenger, R. Garriott, “Method for estimating the spherical aberration of the human crystalline lens in vivo,” Invest. Ophthalmol. Visual Sci. 34, 621–629 (1993).

Hilmantel, G.

G. Hilmantel, R. Blunt, B. Garret, H. Howland, R. Applegate, “Accuracy of the Tomey topographic modeling system in measuring surface elevations of asymmetric objects,” Optom. Vision Sci. 76, 108–114 (1999).
[CrossRef]

Holmgren, D. E.

K. L. Cohen, N. K. Tripoli, D. E. Holmgren, J. M. Coggins, “Assessment of the power and height of radial aspheres reported by a computer-assisted keratoscope,” Am. J. Ophthalmol. 119, 723–732 (1995).
[PubMed]

Hong, X.

L. Thibos, X. Hong, “Clinical application of the Shack–Hartmann aberrometer,” Optom. Vision Sci. 76, 817–825 (1999).
[CrossRef]

Horner, D.

D. Horner, T. Salmon, “Accuracy of the EyeSys 2000 in measuring surface elevation of calibrated aspheres,” Int. Contact Lens Clin. 25, 171–177 (1998).
[CrossRef]

L. Thibos, W. Wheeler, D. Horner, “Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error,” Optom. Vision Sci. 74, 367–375 (1997).
[CrossRef]

R. Mandell, D. Horner, “Alignment of videokeratoscopes,” in An Atlas of Corneal Topography, D. Sanders, D. Kock, eds. (SLACK Inc., Thorofare, N.J., 1993), pp. 197–204.

Howland, H.

T. Oshika, S. Klyce, R. Applegate, H. Howland, “Changes in corneal wavefront aberrations with aging,” Invest. Ophthalmol. Visual Sci. 40, 1351–1355 (1999).

G. Hilmantel, R. Blunt, B. Garret, H. Howland, R. Applegate, “Accuracy of the Tomey topographic modeling system in measuring surface elevations of asymmetric objects,” Optom. Vision Sci. 76, 108–114 (1999).
[CrossRef]

C. Martinez, R. Applegate, S. Klyce, M. McDonald, J. Medina, H. Howland, “Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy,” Arch. Ophthalmol. 116, 1053–1062 (1998).
[CrossRef] [PubMed]

R. Applegate, R. Nunez, J. Buettner, H. Howland, “How accurately can videokeratographic systems measure surface elevation?” Optom. Vision Sci. 72, 785–792 (1995).
[CrossRef]

H. Howland, J. Buettner, R. Applegate, “Computation of the shapes of normal corneas and their monochromatic aberrations from videokeratometric measurements,” in Vision Science and Its Applications, Vol. 2 of 1994 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1994), pp. 54–57.

Howland, H. C.

T. Oshika, S. D. Klyce, R. A. Applegate, H. C. Howland, M. A. ElDanasoury, “Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis,” Am. J. Ophthalmol. 127, 1–7 (1999).
[CrossRef] [PubMed]

Jonasson, F.

E. Gudmundsdottir, F. Jonasson, E. Stefansson, H. Sasaki, K. Sasaki, “Corneal and total astigmatism by age. Does the lens compensate for corneal astigmatism? Reykjavik eye study,” Invest. Ophthalmol. Visual Sci. 41, S303 (2000).

Jones, N.

T. Salmon, C. van de Pol, N. Jones, “ORBSCAN accuracy in measuring corneal surface elevation,” (U.S. Army Aeromedical Research Laboratory, Fort Rucker, Ala., 2000).

Klein, S.

S. Klein, “Optimal corneal ablation for eyes with arbitrary Hartmann–Shack aberrations,” J. Opt. Soc. Am. A 15, 2580–2588 (1998).
[CrossRef]

R. Mandell, C. Chiang, S. Klein, “Location of the major corneal reference points,” Optom. Vision Sci. 72, 776–784 (1995).
[CrossRef]

Klyce, S.

T. Oshika, S. Klyce, R. Applegate, H. Howland, “Changes in corneal wavefront aberrations with aging,” Invest. Ophthalmol. Visual Sci. 40, 1351–1355 (1999).

C. Martinez, R. Applegate, S. Klyce, M. McDonald, J. Medina, H. Howland, “Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy,” Arch. Ophthalmol. 116, 1053–1062 (1998).
[CrossRef] [PubMed]

Klyce, S. D.

T. Oshika, S. D. Klyce, R. A. Applegate, H. C. Howland, M. A. ElDanasoury, “Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis,” Am. J. Ophthalmol. 127, 1–7 (1999).
[CrossRef] [PubMed]

Liang, J.

Lowman, A.

J. Greivenkamp, M. Mellinger, R. Snyder, J. Schwiegerling, A. Lowman, J. Miller, “Comparison of three videokeratoscopes in measurement of toric test surfaces,” J. Refract. Surg. 12, 229–239 (1996).
[PubMed]

Mandell, R.

R. Mandell, “Locating the corneal sighting center from videokeratography,” J. Refract. Surg. 11, 253–259 (1995).
[PubMed]

R. Mandell, C. Chiang, S. Klein, “Location of the major corneal reference points,” Optom. Vision Sci. 72, 776–784 (1995).
[CrossRef]

R. Mandell, D. Horner, “Alignment of videokeratoscopes,” in An Atlas of Corneal Topography, D. Sanders, D. Kock, eds. (SLACK Inc., Thorofare, N.J., 1993), pp. 197–204.

Mandell, R. B.

R. B. Mandell, “The enigma of the corneal contour,” Contact Lens Assoc. Opthalmol. J. 18, 267–273 (1992).

Marcos, S.

R. Applegate, L. Thibos, A. Bradley, S. Marcos, A. Roorda, T. Salmon, D. Atchison, “Reference axis selection: a subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye,” in Vision Science and Its Applications, V. Lakshminaranayan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington D.C., 2000), pp. 147–149.

Marshall, J.

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

Martinez, C.

C. Martinez, R. Applegate, S. Klyce, M. McDonald, J. Medina, H. Howland, “Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy,” Arch. Ophthalmol. 116, 1053–1062 (1998).
[CrossRef] [PubMed]

McDonald, M.

C. Martinez, R. Applegate, S. Klyce, M. McDonald, J. Medina, H. Howland, “Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy,” Arch. Ophthalmol. 116, 1053–1062 (1998).
[CrossRef] [PubMed]

Medina, J.

C. Martinez, R. Applegate, S. Klyce, M. McDonald, J. Medina, H. Howland, “Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy,” Arch. Ophthalmol. 116, 1053–1062 (1998).
[CrossRef] [PubMed]

Mellinger, M.

J. Greivenkamp, M. Mellinger, R. Snyder, J. Schwiegerling, A. Lowman, J. Miller, “Comparison of three videokeratoscopes in measurement of toric test surfaces,” J. Refract. Surg. 12, 229–239 (1996).
[PubMed]

Miller, D. T.

Miller, J.

J. Greivenkamp, M. Mellinger, R. Snyder, J. Schwiegerling, A. Lowman, J. Miller, “Comparison of three videokeratoscopes in measurement of toric test surfaces,” J. Refract. Surg. 12, 229–239 (1996).
[PubMed]

Millodot, M.

M. Millodot, J. Sivak, “Contribution of the cornea and lens to the spherical aberration of the eye,” Vision Res. 19, 685–687 (1979).
[CrossRef] [PubMed]

Ming, Y.

L. N. Thibos, Y. Ming, X. Zhang, A. Bradley, “Spherical aberration of the reduced schematic eye with elliptical refracting surface,” Optom. Vision Sci. 74, 548–565 (1997).
[CrossRef]

Mora, J.

T. Salmon, C. Rash, J. Mora, “Videokeratoscopic accuracy and its potential use in corneal optics research,” (U.S. Army Aeromedical Research Laboratory, Fort Rucker, Ala., 1998).

Moreno-Barriuso, E.

Mutti, D.

K. Zadnik, D. Mutti, A. Adams, “The repeatability of measurements of the ocular components,” Invest. Ophthalmol. Visual Sci. 33, 2325–2333 (1992).

Navarro, R.

Nunez, R.

R. Applegate, R. Nunez, J. Buettner, H. Howland, “How accurately can videokeratographic systems measure surface elevation?” Optom. Vision Sci. 72, 785–792 (1995).
[CrossRef]

O’Brart, D.

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

Oliver, K.

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

R. Hemenger, A. Tomlinson, K. Oliver, “Corneal optics from videokeratographs,” Ophthalmic Physiol. Opt. 15, 63–68 (1994).
[CrossRef]

Ong, E.

J. He, E. Ong, J. Gwiazda, R. Held, F. Thorn, “Wave-front aberrations in the cornea and the whole eye,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

Oshika, T.

T. Oshika, S. D. Klyce, R. A. Applegate, H. C. Howland, M. A. ElDanasoury, “Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis,” Am. J. Ophthalmol. 127, 1–7 (1999).
[CrossRef] [PubMed]

T. Oshika, S. Klyce, R. Applegate, H. Howland, “Changes in corneal wavefront aberrations with aging,” Invest. Ophthalmol. Visual Sci. 40, 1351–1355 (1999).

Piers, P.

M. Berrio, A. Guirao, M. Redondo, P. Piers, P. Artal, “The contribution of the cornea and internal ocular surfaces to the changes in the aberrations of the eye with age,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

Prieto, P.

Rash, C.

T. Salmon, C. Rash, J. Mora, “Videokeratoscopic accuracy and its potential use in corneal optics research,” (U.S. Army Aeromedical Research Laboratory, Fort Rucker, Ala., 1998).

Redondo, M.

A. Guirao, M. Redondo, P. Artal, “Optical aberrations of the human cornea as a function of age,” J. Opt. Soc. Am. A 17, 1697–1702 (2000).
[CrossRef]

M. Berrio, A. Guirao, M. Redondo, P. Piers, P. Artal, “The contribution of the cornea and internal ocular surfaces to the changes in the aberrations of the eye with age,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

Roorda, A.

R. Applegate, L. Thibos, A. Bradley, S. Marcos, A. Roorda, T. Salmon, D. Atchison, “Reference axis selection: a subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye,” in Vision Science and Its Applications, V. Lakshminaranayan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington D.C., 2000), pp. 147–149.

Salmon, T.

T. Salmon, L. Thibos, “Comparison of the eye’s wave-front aberration measured psychophysically and with the Shack–Hartmann wave-front sensor,” J. Opt. Soc. Am. A 15, 2457–2465 (1998).
[CrossRef]

D. Horner, T. Salmon, “Accuracy of the EyeSys 2000 in measuring surface elevation of calibrated aspheres,” Int. Contact Lens Clin. 25, 171–177 (1998).
[CrossRef]

T. Salmon, L. Thibos, “Relative contribution of the cornea and internal optics to the aberrations of the eye,” Optom. Vision Sci. 75(12s), 235 (1998).

T. Salmon, C. Rash, J. Mora, “Videokeratoscopic accuracy and its potential use in corneal optics research,” (U.S. Army Aeromedical Research Laboratory, Fort Rucker, Ala., 1998).

T. Salmon, L. Thibos, “Relative balance of corneal and internal aberrations in the human eye,” presented at the OSA Annual Meeting, October 4–9, 1998, Baltimore, Maryland.

T. Salmon, C. van de Pol, N. Jones, “ORBSCAN accuracy in measuring corneal surface elevation,” (U.S. Army Aeromedical Research Laboratory, Fort Rucker, Ala., 2000).

T. Salmon, “Corneal contribution to the wavefront aberration of the eye,” Ph.D. thesis (Indiana University, Bloomington, Ind., 1999).

R. Applegate, L. Thibos, A. Bradley, S. Marcos, A. Roorda, T. Salmon, D. Atchison, “Reference axis selection: a subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye,” in Vision Science and Its Applications, V. Lakshminaranayan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington D.C., 2000), pp. 147–149.

Sasaki, H.

E. Gudmundsdottir, F. Jonasson, E. Stefansson, H. Sasaki, K. Sasaki, “Corneal and total astigmatism by age. Does the lens compensate for corneal astigmatism? Reykjavik eye study,” Invest. Ophthalmol. Visual Sci. 41, S303 (2000).

Sasaki, K.

E. Gudmundsdottir, F. Jonasson, E. Stefansson, H. Sasaki, K. Sasaki, “Corneal and total astigmatism by age. Does the lens compensate for corneal astigmatism? Reykjavik eye study,” Invest. Ophthalmol. Visual Sci. 41, S303 (2000).

Schwiegerling, J.

J. Greivenkamp, M. Mellinger, R. Snyder, J. Schwiegerling, A. Lowman, J. Miller, “Comparison of three videokeratoscopes in measurement of toric test surfaces,” J. Refract. Surg. 12, 229–239 (1996).
[PubMed]

L. Thibos, R. Applegate, J. Schwiegerling, R. Webb, and VSIA Standards Taskforce Members, “Standards for reporting the optical aberrations of the eye,” in Vision Science and Its Applications, V. Lakshminarayanan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 2000), pp. 232–244.

Sivak, J.

M. Millodot, J. Sivak, “Contribution of the cornea and lens to the spherical aberration of the eye,” Vision Res. 19, 685–687 (1979).
[CrossRef] [PubMed]

Snyder, R.

J. Greivenkamp, M. Mellinger, R. Snyder, J. Schwiegerling, A. Lowman, J. Miller, “Comparison of three videokeratoscopes in measurement of toric test surfaces,” J. Refract. Surg. 12, 229–239 (1996).
[PubMed]

Stefansson, E.

E. Gudmundsdottir, F. Jonasson, E. Stefansson, H. Sasaki, K. Sasaki, “Corneal and total astigmatism by age. Does the lens compensate for corneal astigmatism? Reykjavik eye study,” Invest. Ophthalmol. Visual Sci. 41, S303 (2000).

Thibos, L.

L. Thibos, “Principles of Hartmann–Shack aberrometry,” J. Refract. Surg. 16, S563–S565 (2000).
[PubMed]

L. Thibos, X. Hong, “Clinical application of the Shack–Hartmann aberrometer,” Optom. Vision Sci. 76, 817–825 (1999).
[CrossRef]

T. Salmon, L. Thibos, “Comparison of the eye’s wave-front aberration measured psychophysically and with the Shack–Hartmann wave-front sensor,” J. Opt. Soc. Am. A 15, 2457–2465 (1998).
[CrossRef]

T. Salmon, L. Thibos, “Relative contribution of the cornea and internal optics to the aberrations of the eye,” Optom. Vision Sci. 75(12s), 235 (1998).

L. Thibos, W. Wheeler, D. Horner, “Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error,” Optom. Vision Sci. 74, 367–375 (1997).
[CrossRef]

L. Thibos, “The chromatic eye: a new reduced-eye model of ocular chromatic aberration in humans,” Appl. Opt. 31, 3594–3600 (1992).
[CrossRef] [PubMed]

L. Thibos, R. Applegate, J. Schwiegerling, R. Webb, and VSIA Standards Taskforce Members, “Standards for reporting the optical aberrations of the eye,” in Vision Science and Its Applications, V. Lakshminarayanan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 2000), pp. 232–244.

T. Salmon, L. Thibos, “Relative balance of corneal and internal aberrations in the human eye,” presented at the OSA Annual Meeting, October 4–9, 1998, Baltimore, Maryland.

R. Applegate, L. Thibos, A. Bradley, S. Marcos, A. Roorda, T. Salmon, D. Atchison, “Reference axis selection: a subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye,” in Vision Science and Its Applications, V. Lakshminaranayan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington D.C., 2000), pp. 147–149.

Thibos, L. N.

L. N. Thibos, Y. Ming, X. Zhang, A. Bradley, “Spherical aberration of the reduced schematic eye with elliptical refracting surface,” Optom. Vision Sci. 74, 548–565 (1997).
[CrossRef]

Thorn, F.

J. He, E. Ong, J. Gwiazda, R. Held, F. Thorn, “Wave-front aberrations in the cornea and the whole eye,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

Tomlinson, A.

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

R. Hemenger, A. Tomlinson, K. Oliver, “Corneal optics from videokeratographs,” Ophthalmic Physiol. Opt. 15, 63–68 (1994).
[CrossRef]

A. Tomlinson, R. Hemenger, R. Garriott, “Method for estimating the spherical aberration of the human crystalline lens in vivo,” Invest. Ophthalmol. Visual Sci. 34, 621–629 (1993).

Tripoli, N. K.

K. L. Cohen, N. K. Tripoli, D. E. Holmgren, J. M. Coggins, “Assessment of the power and height of radial aspheres reported by a computer-assisted keratoscope,” Am. J. Ophthalmol. 119, 723–732 (1995).
[PubMed]

van de Pol, C.

T. Salmon, C. van de Pol, N. Jones, “ORBSCAN accuracy in measuring corneal surface elevation,” (U.S. Army Aeromedical Research Laboratory, Fort Rucker, Ala., 2000).

Vargas-Martin, F.

Verma, S.

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

Webb, R.

L. Thibos, R. Applegate, J. Schwiegerling, R. Webb, and VSIA Standards Taskforce Members, “Standards for reporting the optical aberrations of the eye,” in Vision Science and Its Applications, V. Lakshminarayanan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 2000), pp. 232–244.

Wheeler, W.

L. Thibos, W. Wheeler, D. Horner, “Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error,” Optom. Vision Sci. 74, 367–375 (1997).
[CrossRef]

Williams, D.

P. Artal, A. Guirao, E. Berrio, D. Williams, “Compensation of corneal aberrations by the internal optics in the human eye,” J. Vision 1, 1–8 (2001).
[CrossRef]

Williams, D. R.

Young, T.

T. Young, “On the mechanism of the eye,” Philos. Trans. R. Soc. London 19, 23–88 (1801).
[CrossRef]

Zadnik, K.

K. Zadnik, D. Mutti, A. Adams, “The repeatability of measurements of the ocular components,” Invest. Ophthalmol. Visual Sci. 33, 2325–2333 (1992).

Zhang, X.

L. N. Thibos, Y. Ming, X. Zhang, A. Bradley, “Spherical aberration of the reduced schematic eye with elliptical refracting surface,” Optom. Vision Sci. 74, 548–565 (1997).
[CrossRef]

Am. J. Ophthalmol.

K. L. Cohen, N. K. Tripoli, D. E. Holmgren, J. M. Coggins, “Assessment of the power and height of radial aspheres reported by a computer-assisted keratoscope,” Am. J. Ophthalmol. 119, 723–732 (1995).
[PubMed]

T. Oshika, S. D. Klyce, R. A. Applegate, H. C. Howland, M. A. ElDanasoury, “Comparison of corneal wavefront aberrations after photorefractive keratectomy and laser in situ keratomileusis,” Am. J. Ophthalmol. 127, 1–7 (1999).
[CrossRef] [PubMed]

Appl. Opt.

Arch. Ophthalmol.

C. Martinez, R. Applegate, S. Klyce, M. McDonald, J. Medina, H. Howland, “Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy,” Arch. Ophthalmol. 116, 1053–1062 (1998).
[CrossRef] [PubMed]

Br. J. Ophthamol.

W. A. Douthwaite, “EyeSys corneal topography measurement applied to calibrated ellipsoidal convex surfaces,” Br. J. Ophthamol. 79, 797–801 (1995).
[CrossRef]

Contact Lens Assoc. Opthalmol. J.

R. B. Mandell, “The enigma of the corneal contour,” Contact Lens Assoc. Opthalmol. J. 18, 267–273 (1992).

Int. Contact Lens Clin.

D. Horner, T. Salmon, “Accuracy of the EyeSys 2000 in measuring surface elevation of calibrated aspheres,” Int. Contact Lens Clin. 25, 171–177 (1998).
[CrossRef]

Invest. Ophthalmol. Visual Sci.

A. Tomlinson, R. Hemenger, R. Garriott, “Method for estimating the spherical aberration of the human crystalline lens in vivo,” Invest. Ophthalmol. Visual Sci. 34, 621–629 (1993).

J. He, E. Ong, J. Gwiazda, R. Held, F. Thorn, “Wave-front aberrations in the cornea and the whole eye,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

M. Berrio, A. Guirao, M. Redondo, P. Piers, P. Artal, “The contribution of the cornea and internal ocular surfaces to the changes in the aberrations of the eye with age,” Invest. Ophthalmol. Visual Sci. 41, S105 (2000).

K. Zadnik, D. Mutti, A. Adams, “The repeatability of measurements of the ocular components,” Invest. Ophthalmol. Visual Sci. 33, 2325–2333 (1992).

E. Gudmundsdottir, F. Jonasson, E. Stefansson, H. Sasaki, K. Sasaki, “Corneal and total astigmatism by age. Does the lens compensate for corneal astigmatism? Reykjavik eye study,” Invest. Ophthalmol. Visual Sci. 41, S303 (2000).

T. Oshika, S. Klyce, R. Applegate, H. Howland, “Changes in corneal wavefront aberrations with aging,” Invest. Ophthalmol. Visual Sci. 40, 1351–1355 (1999).

J. Opt. Soc. Am.

J. Opt. Soc. Am. A

P. Prieto, F. Vargas-Martin, S. Goelz, P. Artal, “Analysis of the performance of the Hartmann–Shack sensor in the human eye,” J. Opt. Soc. Am. A 17, 1388–1398 (2000).
[CrossRef]

A. Guirao, M. Redondo, P. Artal, “Optical aberrations of the human cornea as a function of age,” J. Opt. Soc. Am. A 17, 1697–1702 (2000).
[CrossRef]

A. Guirao, P. Artal, “Corneal wave aberration from videokeratoscopy: accuracy and limitations of the procedure,” J. Opt. Soc. Am. A 17, 955–965 (2000).
[CrossRef]

E. Moreno-Barriuso, R. Navarro, “Laser ray tracing versus Hartmann–Shack sensor for measuring optical aberrations in the human eye,” J. Opt. Soc. Am. A 17, 974–985 (2000).
[CrossRef]

J. Liang, B. Grimm, S. Goelz, J. F. Bille, “Objective measurement of wave aberrations of the human eye with the use of a Hartmann–Shack wave-front sensor,” J. Opt. Soc. Am. A 11, 1949–1957 (1994).
[CrossRef]

T. Salmon, L. Thibos, “Comparison of the eye’s wave-front aberration measured psychophysically and with the Shack–Hartmann wave-front sensor,” J. Opt. Soc. Am. A 15, 2457–2465 (1998).
[CrossRef]

S. Klein, “Optimal corneal ablation for eyes with arbitrary Hartmann–Shack aberrations,” J. Opt. Soc. Am. A 15, 2580–2588 (1998).
[CrossRef]

J. Liang, D. R. Williams, “Aberrations and retinal image quality of the normal human eye,” J. Opt. Soc. Am. A 14, 2873–2883 (1997).
[CrossRef]

J. Liang, D. R. Williams, D. T. Miller, “Supernormal vision and high-resolution retinal imaging through adaptive optics,” J. Opt. Soc. Am. A 14, 2884–2892 (1997).
[CrossRef]

J. Refract. Surg.

K. Oliver, R. Hemenger, M. Corbett, D. O’Brart, S. Verma, J. Marshall, A. Tomlinson, “Corneal optical aberrations induced by photorefractive keratectomy,” J. Refract. Surg. 13, 246–254 (1997).
[PubMed]

L. Thibos, “Principles of Hartmann–Shack aberrometry,” J. Refract. Surg. 16, S563–S565 (2000).
[PubMed]

R. Mandell, “Locating the corneal sighting center from videokeratography,” J. Refract. Surg. 11, 253–259 (1995).
[PubMed]

J. Greivenkamp, M. Mellinger, R. Snyder, J. Schwiegerling, A. Lowman, J. Miller, “Comparison of three videokeratoscopes in measurement of toric test surfaces,” J. Refract. Surg. 12, 229–239 (1996).
[PubMed]

J. Vision

P. Artal, A. Guirao, E. Berrio, D. Williams, “Compensation of corneal aberrations by the internal optics in the human eye,” J. Vision 1, 1–8 (2001).
[CrossRef]

Ophthalmic Physiol. Opt.

R. Hemenger, A. Tomlinson, K. Oliver, “Corneal optics from videokeratographs,” Ophthalmic Physiol. Opt. 15, 63–68 (1994).
[CrossRef]

Opt. Lett.

Optom. Vision Sci.

G. Hilmantel, R. Blunt, B. Garret, H. Howland, R. Applegate, “Accuracy of the Tomey topographic modeling system in measuring surface elevations of asymmetric objects,” Optom. Vision Sci. 76, 108–114 (1999).
[CrossRef]

L. Thibos, W. Wheeler, D. Horner, “Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error,” Optom. Vision Sci. 74, 367–375 (1997).
[CrossRef]

L. N. Thibos, Y. Ming, X. Zhang, A. Bradley, “Spherical aberration of the reduced schematic eye with elliptical refracting surface,” Optom. Vision Sci. 74, 548–565 (1997).
[CrossRef]

T. Salmon, L. Thibos, “Relative contribution of the cornea and internal optics to the aberrations of the eye,” Optom. Vision Sci. 75(12s), 235 (1998).

L. Thibos, X. Hong, “Clinical application of the Shack–Hartmann aberrometer,” Optom. Vision Sci. 76, 817–825 (1999).
[CrossRef]

R. Mandell, C. Chiang, S. Klein, “Location of the major corneal reference points,” Optom. Vision Sci. 72, 776–784 (1995).
[CrossRef]

R. Applegate, R. Nunez, J. Buettner, H. Howland, “How accurately can videokeratographic systems measure surface elevation?” Optom. Vision Sci. 72, 785–792 (1995).
[CrossRef]

Philos. Trans. R. Soc. London

T. Young, “On the mechanism of the eye,” Philos. Trans. R. Soc. London 19, 23–88 (1801).
[CrossRef]

Vision Res.

M. Millodot, J. Sivak, “Contribution of the cornea and lens to the spherical aberration of the eye,” Vision Res. 19, 685–687 (1979).
[CrossRef] [PubMed]

Other

T. Salmon, L. Thibos, “Relative balance of corneal and internal aberrations in the human eye,” presented at the OSA Annual Meeting, October 4–9, 1998, Baltimore, Maryland.

T. Salmon, C. Rash, J. Mora, “Videokeratoscopic accuracy and its potential use in corneal optics research,” (U.S. Army Aeromedical Research Laboratory, Fort Rucker, Ala., 1998).

R. Applegate, L. Thibos, A. Bradley, S. Marcos, A. Roorda, T. Salmon, D. Atchison, “Reference axis selection: a subcommittee report of the OSA working group to establish standards for the measurement and reporting of the optical aberration of the eye,” in Vision Science and Its Applications, V. Lakshminaranayan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington D.C., 2000), pp. 147–149.

R. Mandell, D. Horner, “Alignment of videokeratoscopes,” in An Atlas of Corneal Topography, D. Sanders, D. Kock, eds. (SLACK Inc., Thorofare, N.J., 1993), pp. 197–204.

L. Thibos, R. Applegate, J. Schwiegerling, R. Webb, and VSIA Standards Taskforce Members, “Standards for reporting the optical aberrations of the eye,” in Vision Science and Its Applications, V. Lakshminarayanan, ed., Vol. 35 of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 2000), pp. 232–244.

American National Standards Institute, American National Standard for the Safe Use of Lasers (American National Standards Institute–Laser Institute of America, New York, 1993).

H. Howland, J. Buettner, R. Applegate, “Computation of the shapes of normal corneas and their monochromatic aberrations from videokeratometric measurements,” in Vision Science and Its Applications, Vol. 2 of 1994 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1994), pp. 54–57.

T. Salmon, C. van de Pol, N. Jones, “ORBSCAN accuracy in measuring corneal surface elevation,” (U.S. Army Aeromedical Research Laboratory, Fort Rucker, Ala., 2000).

T. Salmon, “Corneal contribution to the wavefront aberration of the eye,” Ph.D. thesis (Indiana University, Bloomington, Ind., 1999).

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Figures (10)

Fig. 1
Fig. 1

The standard videokeratoscope measurement procedure requires the patient to fixate a small light (point F) while the operator aligns the instrument axis (FC) normal to the cornea. The line of sight is defined as the segment connecting the entrance pupil center (E) with the fixation point (F). The pupillary axis (PC) is the line that is orthogonal to the cornea and passes through the entrance pupil (E). Point A represents the intersection of the pupillary axis with the corneal surface. Assuming that the paraxial region of this corneal profile is well approximated by a circle, the keratoscope axis and the pupillary axis intersect at the corneal center of curvature (C). The corneal wave-front aberration and corneal topography measurements should be centered on the line of sight, but if angle lambda (∠λ) between the pupillary axis and the line of sight is not zero, the line of sight will be displaced away from the instrument axis. The point where the line of sight intersects the corneal surface is called the corneal sighting center (S). With normal alignment, as shown here, the corneal topography map will be centered on point V, the corneal apex, which does not coincide with the line of sight, the center of the pupil, or any other standard reference point.

Fig. 2
Fig. 2

A rotationally symmetric mathematical model (apical radius=7.85 mm, p value=0.7, pupil=5.6 mm) was used to compute the change in the corneal wave-front aberration for different values of horizontal angle lambda. For normal angle lambda values (1.4°–9°), significant changes were noted in the Zernike modes labeled tilt, astigmatism, and primary coma. The magnitude of the change in these Zernike coefficients as a function of angle lambda is plotted here.

Fig. 3
Fig. 3

Radially averaged surface elevation (sag) error of the EyeSys videokeratoscope, calibrated against ellipsoidal test surfaces, with apical radii (in millimeters) and p values listed in the insets (radius/p value). Plots show error using the machine default algorithms (top), as a relative proportion of the sag measurement (middle), and after compensation for systematic instrument error (bottom). Negative values indicate that the measurement underestimates the corneal sag.

Fig. 4
Fig. 4

The corneal wave-front aberration function was computed as the difference between the chief ray (OSI) and optical paths traced through each of the corneal surface points (B) sampled by the videokeratoscope. The chief ray was defined to coincide with the line of sight in object space (OS), with object point (O) located 10,000 m away from the eye on the line of sight. After refraction at the corneal surface, we traced the chief ray to the paraxial image point (I). Point S, known as the corneal sighting center, is the intersection of the line of sight with the corneal surface. Point F is the videokeratoscope fixation point. The instrument axis (VK axis) is also shown.

Fig. 5
Fig. 5

Repeatability of EyeSys surface elevation in terms of radially averaged standard errors, in micrometers (left ordinate), or corresponding wave-front error (right ordinate), in wavelengths (λ=633nm), plotted as a function of radial distance from the center in millimeters. Elevation data obtained from 15–19 images were averaged to give mean surface elevations and standard errors at approximately 4000 points. Each ring contained 360 points, all at approximately the same radial distance from the center of the cornea. For each subject, the means of 360 standard errors within each ring are plotted here.The curve shows a second-order polynomial fit to all data points.

Fig. 6
Fig. 6

Contour plots showing the higher-order wave-front aberrations (Zernike orders 3–10, modes 6–65) for the cornea (left column), the internal optics (middle column), and the eye (right column) for three subjects.Contour lines indicate 0.3λ intervals (λ=633nm); dashed lines show negative contour values. Aberrations of the cornea combine with those of the internal optics to make the higher-order aberrations of the eye.As summarized by the wave-front variances in Table 3, AB had partial corneal/internal aberration balancing; DH’s balance was poor, and LT showed the most effective overall balance.Row LT shows the corneal and internal aberration contours that would have resulted if LT’s VK-LOS misalignment had not been corrected. Noncompensation for VK tilt would have made no discernible difference in the corneal and internal wave-front plots for subjects AB and DH.Pupil sizes for subjects AB and LT were 5.6 mm; for DH it was 5.2 mm.

Fig. 7
Fig. 7

Breakdown of corneal higher-order aberrations per Zernike order for each subject, with (black bars) and without (gray bars) compensation for VK-LOS misalignment.Vertical axis units are wave-front variance in wavelengths squared (λ=633nm).

Fig. 8
Fig. 8

Breakdown of ocular higher-order aberrations per Zernike order for each subject, expressed as a percentage of the total higher-order wave-front variance for each eye.

Fig. 9
Fig. 9

Breakdown of internal higher-order aberrations per Zernike order for each subject, with (black bars) and without (gray bars) compensation for VK-LOS misalignment.Vertical axis units are wave-front variance in wavelengths squared (λ=633nm).

Fig. 10
Fig. 10

Mode-by-mode analysis of corneal/internal aberration balancing for modes 6–14 (Zernike orders 3, 4) for AB (top row), DH (middle row), and LT (bottom row).The left column shows results with compensation for VK-LOS misalignment; the right column shows results without compensation.Lengths of the bars indicate the magnitude of corneal (dark bars) and internal (gray bars) coefficients in wavelengths (λ=633nm) for each mode (OSA single-index scheme). Perfect aberration balancing occurs when the corneal and internal coefficients are equal in magnitude but opposite in sign; for example, mode 8 in subject DH. When coefficients have the same sign, bars stack (do not overlap) in the same direction. Higher modes (Zernike orders 5–10) were excluded, since they contribute relatively little to the corneal and internal higher-order wave-front aberrations.

Tables (4)

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Table 1 Parameters Used To Compute the Location of the Corneal Sighting Center for the Right Eye of Each Subjecta

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Table 2 Comparison of Clinically Measured and Wave-front-Derived Values for Corneal, Ocular, and Internal Astigmatism, Expressed in Clinical Minus Cylinder Notationa

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Table 3 Wave-Front Variances in Wavelengths Squared (λ=633 nm) for Corneal, Ocular, and Internal Aberrations and Percent of Corneal Aberrations Corrected by the Internal Optics (Corneal to Ocular Change)a

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Table 4 Summary of Possible Values for J45 and J180a

Equations (22)

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slope=0.0032p-0.00342.
intercept=0.0037p-0.0003,
rse=slope(d)+intercept,
se=sag(1-rse).
ra=(1-p)d2+r0.
SA=SE(λ),
FP=(FS+SE)(λ),
VA=FP(VC/FC),
x=VA-SA.
cornealtoocularchange=(ocular-corneal)/corneal.
J45=(-26/y2)(Z2-2),
M=(-43/y2)(Z20),
J180=(-26/y2)(Z22).
cylinder=-2(J1802+J452)1/2,
sphere=M-cylinder/2,
axis=tan-1(J45/J180)2.
IF(J180=0, IF(J45<0, 135, 45),
IF(J180<0, axis+90,
IF(J450, axis+180, axis))).
IF(J180=0, IF(J45>0, 135, 45),
IF(J180>0, axis+90,
IF(J450, axis+180, axis))).

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