Abstract

This paper describes a new method for determining corneal surface detail utilizing a modified Zeiss photo slit lamp. This system projects a grid onto the cornea through a cobalt blue filter. The tear film is stained with fluorescein, causing the projected grid pattern to be visible on the corneal surface. A video image of the grid is then digitized by an image processor which calculates surface detail by evaluating the distortion of the grid lines. Information on curvature and surface detail is obtained across the full corneal surface, both the central optical axis and peripherally beyond the limbus.

© 1988 Optical Society of America

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  1. J. J. Rowsey, H. Gelinder, J. Krachmer, P. Laibson et al., “PERK Corneal Topography Predicts Refractive Results in Radial Keratometry,” Ophthalmology 93 (8) (Suppl.), 94 (1986).
  2. L. J. Maguire, S. D. Klyce, D. E. Singer et al., “Corneal Topography in Myopic Patients Undergoing Epikeratophakia,” Am. J. Ophthalmol. 103, 404 (1987).
    [PubMed]
  3. J. J. Rowsey, A. E. Reynold, R. Brown, “Corneal Topography,” Arch. Ophthalmol. 99, 1093 (1981).
    [CrossRef] [PubMed]
  4. P. S. Binder, “Selective Suture Removal Can Reduce Postkeratoplasty Astigmatism,” Ophthalmology 92, 1412 (1985).
    [PubMed]
  5. B. A. J. Clark, “Autocollimating Photokeratoscope,” J. Opt. Soc. Am. 62, 169 (1972).
    [CrossRef] [PubMed]
  6. Stewart Duke-Elder, D. Abrams, “Chapter III The Dioptic Imagry of the Eye,” Syst. Ophthalmol. Ophthal. Opt. Refraction 5, 128 (1970).
  7. J. D. Doss, R. L. Hutson, J. J. Rowsey, D. R. Brown, “Method for Calculation of Corneal Profile and Power Distribution,” Arch. Ophthalmol. 99, 1261 (1981).
    [CrossRef] [PubMed]
  8. S. D. Klyce, “Computer-Assisted Corneal Topography. High Resolution Graphic Presentation and Analysis of Keratoscopy,” Invest. Ophthalmol. Vision Sci. 25, 1426 (1984).
  9. W. Frobin, E. Hierholzer, “Rasterstereography: A Photogrammetric Method for Measurement of Body Surfaces,” J. Biol. Photogr. 51, 11 (1Jan.1983).
    [PubMed]
  10. J. W. Koepfler, “Moire Topography in Medicine,” J. Biol. Photogr. 51, (1Jan.1983).
    [PubMed]
  11. R. Bonnett, “New Method of Topographical Ophthalmometry—Its Theoretical and Clinical Applications,” Am. J. Opt. 39, 227 (1962).
    [CrossRef]
  12. M. R. Nelson, J. L. Cambier, S. I. Brown, P. G. Rehkopf, J. W. Warnicki, “System for Acquisition, Analysis, and Archiving of Ophthalmic Images (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 12, 72 (1984).
  13. P. G. Rehkopf, J. W. Warnicki, “Clinical Experience with the Ophthalmic Image Processing System (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 13, 282 (1985).
  14. P. G Rehkopf, J. W. Warnicki, M. R. Nelson, J. Cambier, S. I. Brown, “Image Processing in Opthalmology. A New Clinical Noninvasive Diagnostic Modality,” in Technical Digest, Noninvasive Assessment of the Visual System (Optical Society of America, Washington, DC, (1985), paper WA2.
  15. J. W. Warnicki, P. G. Rehkopf, J. L. Cambier, M. R. Nelson, “Development of an Imaging System for Ophthalmic Photography,” J. Biol. Photog. 53, 9 (1985).
  16. Grid lines were projected onto a calibration object with a flat surface. The spacing between the lines has been measured and the distortions occurring from off-axis projection analyzed and quantified. Images are then normalized using this analysis.
  17. M. S. Caceci, W. P. Cacheris, “Fitting Curves to Data,” Byte (May1984).
  18. J. D. Foley, A. Van Dam, Fundamentals of Interactive Computer Graphics (Addison-Wesley, Reading, PA, 1982).

1987 (1)

L. J. Maguire, S. D. Klyce, D. E. Singer et al., “Corneal Topography in Myopic Patients Undergoing Epikeratophakia,” Am. J. Ophthalmol. 103, 404 (1987).
[PubMed]

1986 (1)

J. J. Rowsey, H. Gelinder, J. Krachmer, P. Laibson et al., “PERK Corneal Topography Predicts Refractive Results in Radial Keratometry,” Ophthalmology 93 (8) (Suppl.), 94 (1986).

1985 (3)

P. S. Binder, “Selective Suture Removal Can Reduce Postkeratoplasty Astigmatism,” Ophthalmology 92, 1412 (1985).
[PubMed]

P. G. Rehkopf, J. W. Warnicki, “Clinical Experience with the Ophthalmic Image Processing System (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 13, 282 (1985).

J. W. Warnicki, P. G. Rehkopf, J. L. Cambier, M. R. Nelson, “Development of an Imaging System for Ophthalmic Photography,” J. Biol. Photog. 53, 9 (1985).

1984 (2)

S. D. Klyce, “Computer-Assisted Corneal Topography. High Resolution Graphic Presentation and Analysis of Keratoscopy,” Invest. Ophthalmol. Vision Sci. 25, 1426 (1984).

M. R. Nelson, J. L. Cambier, S. I. Brown, P. G. Rehkopf, J. W. Warnicki, “System for Acquisition, Analysis, and Archiving of Ophthalmic Images (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 12, 72 (1984).

1983 (2)

W. Frobin, E. Hierholzer, “Rasterstereography: A Photogrammetric Method for Measurement of Body Surfaces,” J. Biol. Photogr. 51, 11 (1Jan.1983).
[PubMed]

J. W. Koepfler, “Moire Topography in Medicine,” J. Biol. Photogr. 51, (1Jan.1983).
[PubMed]

1981 (2)

J. D. Doss, R. L. Hutson, J. J. Rowsey, D. R. Brown, “Method for Calculation of Corneal Profile and Power Distribution,” Arch. Ophthalmol. 99, 1261 (1981).
[CrossRef] [PubMed]

J. J. Rowsey, A. E. Reynold, R. Brown, “Corneal Topography,” Arch. Ophthalmol. 99, 1093 (1981).
[CrossRef] [PubMed]

1972 (1)

1970 (1)

Stewart Duke-Elder, D. Abrams, “Chapter III The Dioptic Imagry of the Eye,” Syst. Ophthalmol. Ophthal. Opt. Refraction 5, 128 (1970).

1962 (1)

R. Bonnett, “New Method of Topographical Ophthalmometry—Its Theoretical and Clinical Applications,” Am. J. Opt. 39, 227 (1962).
[CrossRef]

Abrams, D.

Stewart Duke-Elder, D. Abrams, “Chapter III The Dioptic Imagry of the Eye,” Syst. Ophthalmol. Ophthal. Opt. Refraction 5, 128 (1970).

Binder, P. S.

P. S. Binder, “Selective Suture Removal Can Reduce Postkeratoplasty Astigmatism,” Ophthalmology 92, 1412 (1985).
[PubMed]

Bonnett, R.

R. Bonnett, “New Method of Topographical Ophthalmometry—Its Theoretical and Clinical Applications,” Am. J. Opt. 39, 227 (1962).
[CrossRef]

Brown, D. R.

J. D. Doss, R. L. Hutson, J. J. Rowsey, D. R. Brown, “Method for Calculation of Corneal Profile and Power Distribution,” Arch. Ophthalmol. 99, 1261 (1981).
[CrossRef] [PubMed]

Brown, R.

J. J. Rowsey, A. E. Reynold, R. Brown, “Corneal Topography,” Arch. Ophthalmol. 99, 1093 (1981).
[CrossRef] [PubMed]

Brown, S. I.

M. R. Nelson, J. L. Cambier, S. I. Brown, P. G. Rehkopf, J. W. Warnicki, “System for Acquisition, Analysis, and Archiving of Ophthalmic Images (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 12, 72 (1984).

P. G Rehkopf, J. W. Warnicki, M. R. Nelson, J. Cambier, S. I. Brown, “Image Processing in Opthalmology. A New Clinical Noninvasive Diagnostic Modality,” in Technical Digest, Noninvasive Assessment of the Visual System (Optical Society of America, Washington, DC, (1985), paper WA2.

Caceci, M. S.

M. S. Caceci, W. P. Cacheris, “Fitting Curves to Data,” Byte (May1984).

Cacheris, W. P.

M. S. Caceci, W. P. Cacheris, “Fitting Curves to Data,” Byte (May1984).

Cambier, J.

P. G Rehkopf, J. W. Warnicki, M. R. Nelson, J. Cambier, S. I. Brown, “Image Processing in Opthalmology. A New Clinical Noninvasive Diagnostic Modality,” in Technical Digest, Noninvasive Assessment of the Visual System (Optical Society of America, Washington, DC, (1985), paper WA2.

Cambier, J. L.

J. W. Warnicki, P. G. Rehkopf, J. L. Cambier, M. R. Nelson, “Development of an Imaging System for Ophthalmic Photography,” J. Biol. Photog. 53, 9 (1985).

M. R. Nelson, J. L. Cambier, S. I. Brown, P. G. Rehkopf, J. W. Warnicki, “System for Acquisition, Analysis, and Archiving of Ophthalmic Images (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 12, 72 (1984).

Clark, B. A. J.

Doss, J. D.

J. D. Doss, R. L. Hutson, J. J. Rowsey, D. R. Brown, “Method for Calculation of Corneal Profile and Power Distribution,” Arch. Ophthalmol. 99, 1261 (1981).
[CrossRef] [PubMed]

Duke-Elder, Stewart

Stewart Duke-Elder, D. Abrams, “Chapter III The Dioptic Imagry of the Eye,” Syst. Ophthalmol. Ophthal. Opt. Refraction 5, 128 (1970).

Foley, J. D.

J. D. Foley, A. Van Dam, Fundamentals of Interactive Computer Graphics (Addison-Wesley, Reading, PA, 1982).

Frobin, W.

W. Frobin, E. Hierholzer, “Rasterstereography: A Photogrammetric Method for Measurement of Body Surfaces,” J. Biol. Photogr. 51, 11 (1Jan.1983).
[PubMed]

Gelinder, H.

J. J. Rowsey, H. Gelinder, J. Krachmer, P. Laibson et al., “PERK Corneal Topography Predicts Refractive Results in Radial Keratometry,” Ophthalmology 93 (8) (Suppl.), 94 (1986).

Hierholzer, E.

W. Frobin, E. Hierholzer, “Rasterstereography: A Photogrammetric Method for Measurement of Body Surfaces,” J. Biol. Photogr. 51, 11 (1Jan.1983).
[PubMed]

Hutson, R. L.

J. D. Doss, R. L. Hutson, J. J. Rowsey, D. R. Brown, “Method for Calculation of Corneal Profile and Power Distribution,” Arch. Ophthalmol. 99, 1261 (1981).
[CrossRef] [PubMed]

Klyce, S. D.

L. J. Maguire, S. D. Klyce, D. E. Singer et al., “Corneal Topography in Myopic Patients Undergoing Epikeratophakia,” Am. J. Ophthalmol. 103, 404 (1987).
[PubMed]

S. D. Klyce, “Computer-Assisted Corneal Topography. High Resolution Graphic Presentation and Analysis of Keratoscopy,” Invest. Ophthalmol. Vision Sci. 25, 1426 (1984).

Koepfler, J. W.

J. W. Koepfler, “Moire Topography in Medicine,” J. Biol. Photogr. 51, (1Jan.1983).
[PubMed]

Krachmer, J.

J. J. Rowsey, H. Gelinder, J. Krachmer, P. Laibson et al., “PERK Corneal Topography Predicts Refractive Results in Radial Keratometry,” Ophthalmology 93 (8) (Suppl.), 94 (1986).

Laibson, P.

J. J. Rowsey, H. Gelinder, J. Krachmer, P. Laibson et al., “PERK Corneal Topography Predicts Refractive Results in Radial Keratometry,” Ophthalmology 93 (8) (Suppl.), 94 (1986).

Maguire, L. J.

L. J. Maguire, S. D. Klyce, D. E. Singer et al., “Corneal Topography in Myopic Patients Undergoing Epikeratophakia,” Am. J. Ophthalmol. 103, 404 (1987).
[PubMed]

Nelson, M. R.

J. W. Warnicki, P. G. Rehkopf, J. L. Cambier, M. R. Nelson, “Development of an Imaging System for Ophthalmic Photography,” J. Biol. Photog. 53, 9 (1985).

M. R. Nelson, J. L. Cambier, S. I. Brown, P. G. Rehkopf, J. W. Warnicki, “System for Acquisition, Analysis, and Archiving of Ophthalmic Images (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 12, 72 (1984).

P. G Rehkopf, J. W. Warnicki, M. R. Nelson, J. Cambier, S. I. Brown, “Image Processing in Opthalmology. A New Clinical Noninvasive Diagnostic Modality,” in Technical Digest, Noninvasive Assessment of the Visual System (Optical Society of America, Washington, DC, (1985), paper WA2.

Rehkopf, P. G

P. G Rehkopf, J. W. Warnicki, M. R. Nelson, J. Cambier, S. I. Brown, “Image Processing in Opthalmology. A New Clinical Noninvasive Diagnostic Modality,” in Technical Digest, Noninvasive Assessment of the Visual System (Optical Society of America, Washington, DC, (1985), paper WA2.

Rehkopf, P. G.

P. G. Rehkopf, J. W. Warnicki, “Clinical Experience with the Ophthalmic Image Processing System (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 13, 282 (1985).

J. W. Warnicki, P. G. Rehkopf, J. L. Cambier, M. R. Nelson, “Development of an Imaging System for Ophthalmic Photography,” J. Biol. Photog. 53, 9 (1985).

M. R. Nelson, J. L. Cambier, S. I. Brown, P. G. Rehkopf, J. W. Warnicki, “System for Acquisition, Analysis, and Archiving of Ophthalmic Images (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 12, 72 (1984).

Reynold, A. E.

J. J. Rowsey, A. E. Reynold, R. Brown, “Corneal Topography,” Arch. Ophthalmol. 99, 1093 (1981).
[CrossRef] [PubMed]

Rowsey, J. J.

J. J. Rowsey, H. Gelinder, J. Krachmer, P. Laibson et al., “PERK Corneal Topography Predicts Refractive Results in Radial Keratometry,” Ophthalmology 93 (8) (Suppl.), 94 (1986).

J. J. Rowsey, A. E. Reynold, R. Brown, “Corneal Topography,” Arch. Ophthalmol. 99, 1093 (1981).
[CrossRef] [PubMed]

J. D. Doss, R. L. Hutson, J. J. Rowsey, D. R. Brown, “Method for Calculation of Corneal Profile and Power Distribution,” Arch. Ophthalmol. 99, 1261 (1981).
[CrossRef] [PubMed]

Singer, D. E.

L. J. Maguire, S. D. Klyce, D. E. Singer et al., “Corneal Topography in Myopic Patients Undergoing Epikeratophakia,” Am. J. Ophthalmol. 103, 404 (1987).
[PubMed]

Van Dam, A.

J. D. Foley, A. Van Dam, Fundamentals of Interactive Computer Graphics (Addison-Wesley, Reading, PA, 1982).

Warnicki, J. W.

J. W. Warnicki, P. G. Rehkopf, J. L. Cambier, M. R. Nelson, “Development of an Imaging System for Ophthalmic Photography,” J. Biol. Photog. 53, 9 (1985).

P. G. Rehkopf, J. W. Warnicki, “Clinical Experience with the Ophthalmic Image Processing System (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 13, 282 (1985).

M. R. Nelson, J. L. Cambier, S. I. Brown, P. G. Rehkopf, J. W. Warnicki, “System for Acquisition, Analysis, and Archiving of Ophthalmic Images (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 12, 72 (1984).

P. G Rehkopf, J. W. Warnicki, M. R. Nelson, J. Cambier, S. I. Brown, “Image Processing in Opthalmology. A New Clinical Noninvasive Diagnostic Modality,” in Technical Digest, Noninvasive Assessment of the Visual System (Optical Society of America, Washington, DC, (1985), paper WA2.

Am. J. Ophthalmol. (1)

L. J. Maguire, S. D. Klyce, D. E. Singer et al., “Corneal Topography in Myopic Patients Undergoing Epikeratophakia,” Am. J. Ophthalmol. 103, 404 (1987).
[PubMed]

Am. J. Opt. (1)

R. Bonnett, “New Method of Topographical Ophthalmometry—Its Theoretical and Clinical Applications,” Am. J. Opt. 39, 227 (1962).
[CrossRef]

Arch. Ophthalmol. (2)

J. D. Doss, R. L. Hutson, J. J. Rowsey, D. R. Brown, “Method for Calculation of Corneal Profile and Power Distribution,” Arch. Ophthalmol. 99, 1261 (1981).
[CrossRef] [PubMed]

J. J. Rowsey, A. E. Reynold, R. Brown, “Corneal Topography,” Arch. Ophthalmol. 99, 1093 (1981).
[CrossRef] [PubMed]

Invest. Ophthalmol. Vision Sci. (1)

S. D. Klyce, “Computer-Assisted Corneal Topography. High Resolution Graphic Presentation and Analysis of Keratoscopy,” Invest. Ophthalmol. Vision Sci. 25, 1426 (1984).

J. Biol. Photog. (1)

J. W. Warnicki, P. G. Rehkopf, J. L. Cambier, M. R. Nelson, “Development of an Imaging System for Ophthalmic Photography,” J. Biol. Photog. 53, 9 (1985).

J. Biol. Photogr. (2)

W. Frobin, E. Hierholzer, “Rasterstereography: A Photogrammetric Method for Measurement of Body Surfaces,” J. Biol. Photogr. 51, 11 (1Jan.1983).
[PubMed]

J. W. Koepfler, “Moire Topography in Medicine,” J. Biol. Photogr. 51, (1Jan.1983).
[PubMed]

J. Opt. Soc. Am. (1)

Ophthalmology (2)

P. S. Binder, “Selective Suture Removal Can Reduce Postkeratoplasty Astigmatism,” Ophthalmology 92, 1412 (1985).
[PubMed]

J. J. Rowsey, H. Gelinder, J. Krachmer, P. Laibson et al., “PERK Corneal Topography Predicts Refractive Results in Radial Keratometry,” Ophthalmology 93 (8) (Suppl.), 94 (1986).

Proc. Soc. Photo-Opt. Instrum. Eng. (2)

M. R. Nelson, J. L. Cambier, S. I. Brown, P. G. Rehkopf, J. W. Warnicki, “System for Acquisition, Analysis, and Archiving of Ophthalmic Images (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 12, 72 (1984).

P. G. Rehkopf, J. W. Warnicki, “Clinical Experience with the Ophthalmic Image Processing System (IS 2000),” Proc. Soc. Photo-Opt. Instrum. Eng. 13, 282 (1985).

Syst. Ophthalmol. Ophthal. Opt. Refraction (1)

Stewart Duke-Elder, D. Abrams, “Chapter III The Dioptic Imagry of the Eye,” Syst. Ophthalmol. Ophthal. Opt. Refraction 5, 128 (1970).

Other (4)

Grid lines were projected onto a calibration object with a flat surface. The spacing between the lines has been measured and the distortions occurring from off-axis projection analyzed and quantified. Images are then normalized using this analysis.

M. S. Caceci, W. P. Cacheris, “Fitting Curves to Data,” Byte (May1984).

J. D. Foley, A. Van Dam, Fundamentals of Interactive Computer Graphics (Addison-Wesley, Reading, PA, 1982).

P. G Rehkopf, J. W. Warnicki, M. R. Nelson, J. Cambier, S. I. Brown, “Image Processing in Opthalmology. A New Clinical Noninvasive Diagnostic Modality,” in Technical Digest, Noninvasive Assessment of the Visual System (Optical Society of America, Washington, DC, (1985), paper WA2.

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Figures (10)

Fig. 1
Fig. 1

(a) Placido disk photograph of a normal spherical cornea photographed with the sun photokeratoscope model PKS-1000. (b) Corneal transplant patient with astigmatic central cornea.

Fig. 2
Fig. 2

Vertical grid projected on eye. Horizontal lines of black dots are an artifact from a bad memory chip in the image processor.

Fig. 3
Fig. 3

Schematic diagram of Zeiss microscope with beam splitter and projection system attached.

Fig. 4
Fig. 4

Intensity plot of center line across cornea on top, normalized below.

Fig. 5
Fig. 5

Schematic diagram showing grid lines displaced on cornea from assumed normal position and trigonometric solution for elevation.

Fig. 6
Fig. 6

Orthogonal view of normal cornea on left; same cornea with common curve removed on right.

Fig. 7
Fig. 7

Contour plot of cornea. Each line represents an elevation change of 0.1 mm.

Fig. 8
Fig. 8

2.5× optical magnification of the center of the cornea before processing. Each contour line represents 0.0125 mm in elevation.

Fig. 9
Fig. 9

Contour plot of a cornea with astigmatism.

Fig. 10
Fig. 10

Graph comparing grid curvature measurements with micrometer readings; four points plotted for each steel ball.

Equations (3)

Equations on this page are rendered with MathJax. Learn more.

new value = ( L prev L min ) × ( 256 / L max L min ) ,
deviation of grid = ( lines shifted × SP ) horizontal distance ,
elevation = [ ( deviation of grid / sine α ) × cos β ] / magnification ratio ,

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