Abstract

We present an algorithm to process images of reflected Placido rings captured by a commercial videokeratoscope. Raw data are obtained with no Cartesian-to-polar-coordinate conversion, thus avoiding interpolation and associated numerical artifacts. The method provides a characteristic equation for the device and is able to process around 6 times more corneal data than the commercial software. Our proposal allows complete control over the whole process from the capture of corneal images until the computation of curvature radii.

© 2013 Optical Society of America

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References

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  1. T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
    [CrossRef]
  2. D. R. Iskander and M. J. Collins, “Applications of high-speed videokeratoscopy,” Clin. Exp. Optom. 88, 399–407 (2004).
    [CrossRef]
  3. W. Tang, M. J. Collins, L. Carney, and B. Davis, “The accuracy and precision performance of four videokeratoscopes in measuring test surfaces,” Optom. Vis. Sci. 77, 483–491 (2000).
    [CrossRef]
  4. P. Cho, A. K. C. Lam, J. Mountford, and L. Ng, “The performance of four different corneal topographers on normal human corneas and its impact on orthokeratology lens fitting,” Optom. Vis. Sci. 79, 175–183 (2002).
    [CrossRef]
  5. S. A. Read, M. J. Collins, L. G. Carney, and R. J. Franklin, “The topography of the central and peripheral cornea,” Invest. Ophthalmol. Visual Sci. 47, 1404–1415 (2006).
    [CrossRef]
  6. D. Mas, M. A. Kowalska, J. Espinosa, and H. Kasprzak, “Custom design dynamic videokeratometer,” J. Mod. Opt. 57, 94–102 (2010).
    [CrossRef]
  7. J. Serra, Image Analysis and Mathematical Morphology(Academic, 1983).
  8. L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
    [CrossRef]
  9. C. Roberts, “Characterization of the inherent error in a spherically-biased corneal topography system in mapping a radially aspheric surface,” J. Refract. Corneal Surg. 10, 103–111 (1994).
  10. S. A. Klein, “Corneal topography: a review, new ANSI standards and problems to solve,” in Vision Science and its Applications, OSA Technical Digest (Optical Society of America, 2000), paper NW8.
  11. J. Espinosa, J. Pérez, D. Mas, and C. Illueca, “Weighted Zernike polynomial fitting in steep corneas sampled in Cartesian grid,” J. Mod. Opt. 58, 1710–1715 (2011).
    [CrossRef]

2011

J. Espinosa, J. Pérez, D. Mas, and C. Illueca, “Weighted Zernike polynomial fitting in steep corneas sampled in Cartesian grid,” J. Mod. Opt. 58, 1710–1715 (2011).
[CrossRef]

2010

D. Mas, M. A. Kowalska, J. Espinosa, and H. Kasprzak, “Custom design dynamic videokeratometer,” J. Mod. Opt. 57, 94–102 (2010).
[CrossRef]

2006

S. A. Read, M. J. Collins, L. G. Carney, and R. J. Franklin, “The topography of the central and peripheral cornea,” Invest. Ophthalmol. Visual Sci. 47, 1404–1415 (2006).
[CrossRef]

2004

D. R. Iskander and M. J. Collins, “Applications of high-speed videokeratoscopy,” Clin. Exp. Optom. 88, 399–407 (2004).
[CrossRef]

2003

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

2002

P. Cho, A. K. C. Lam, J. Mountford, and L. Ng, “The performance of four different corneal topographers on normal human corneas and its impact on orthokeratology lens fitting,” Optom. Vis. Sci. 79, 175–183 (2002).
[CrossRef]

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

2000

W. Tang, M. J. Collins, L. Carney, and B. Davis, “The accuracy and precision performance of four videokeratoscopes in measuring test surfaces,” Optom. Vis. Sci. 77, 483–491 (2000).
[CrossRef]

1994

C. Roberts, “Characterization of the inherent error in a spherically-biased corneal topography system in mapping a radially aspheric surface,” J. Refract. Corneal Surg. 10, 103–111 (1994).

Bessyo, T.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Carney, L.

W. Tang, M. J. Collins, L. Carney, and B. Davis, “The accuracy and precision performance of four videokeratoscopes in measuring test surfaces,” Optom. Vis. Sci. 77, 483–491 (2000).
[CrossRef]

Carney, L. G.

S. A. Read, M. J. Collins, L. G. Carney, and R. J. Franklin, “The topography of the central and peripheral cornea,” Invest. Ophthalmol. Visual Sci. 47, 1404–1415 (2006).
[CrossRef]

Castro, J. C.

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

Chamon, W.

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

Cho, P.

P. Cho, A. K. C. Lam, J. Mountford, and L. Ng, “The performance of four different corneal topographers on normal human corneas and its impact on orthokeratology lens fitting,” Optom. Vis. Sci. 79, 175–183 (2002).
[CrossRef]

Collins, M. J.

S. A. Read, M. J. Collins, L. G. Carney, and R. J. Franklin, “The topography of the central and peripheral cornea,” Invest. Ophthalmol. Visual Sci. 47, 1404–1415 (2006).
[CrossRef]

D. R. Iskander and M. J. Collins, “Applications of high-speed videokeratoscopy,” Clin. Exp. Optom. 88, 399–407 (2004).
[CrossRef]

W. Tang, M. J. Collins, L. Carney, and B. Davis, “The accuracy and precision performance of four videokeratoscopes in measuring test surfaces,” Optom. Vis. Sci. 77, 483–491 (2000).
[CrossRef]

Davis, B.

W. Tang, M. J. Collins, L. Carney, and B. Davis, “The accuracy and precision performance of four videokeratoscopes in measuring test surfaces,” Optom. Vis. Sci. 77, 483–491 (2000).
[CrossRef]

De Carvalho, L. A. V.

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

Espinosa, J.

J. Espinosa, J. Pérez, D. Mas, and C. Illueca, “Weighted Zernike polynomial fitting in steep corneas sampled in Cartesian grid,” J. Mod. Opt. 58, 1710–1715 (2011).
[CrossRef]

D. Mas, M. A. Kowalska, J. Espinosa, and H. Kasprzak, “Custom design dynamic videokeratometer,” J. Mod. Opt. 57, 94–102 (2010).
[CrossRef]

Franklin, R. J.

S. A. Read, M. J. Collins, L. G. Carney, and R. J. Franklin, “The topography of the central and peripheral cornea,” Invest. Ophthalmol. Visual Sci. 47, 1404–1415 (2006).
[CrossRef]

Goto, T.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Illueca, C.

J. Espinosa, J. Pérez, D. Mas, and C. Illueca, “Weighted Zernike polynomial fitting in steep corneas sampled in Cartesian grid,” J. Mod. Opt. 58, 1710–1715 (2011).
[CrossRef]

Iskander, D. R.

D. R. Iskander and M. J. Collins, “Applications of high-speed videokeratoscopy,” Clin. Exp. Optom. 88, 399–407 (2004).
[CrossRef]

Karon, M.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Kasprzak, H.

D. Mas, M. A. Kowalska, J. Espinosa, and H. Kasprzak, “Custom design dynamic videokeratometer,” J. Mod. Opt. 57, 94–102 (2010).
[CrossRef]

Kataoka, H.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Klein, S. A.

S. A. Klein, “Corneal topography: a review, new ANSI standards and problems to solve,” in Vision Science and its Applications, OSA Technical Digest (Optical Society of America, 2000), paper NW8.

Klyce, S. D.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Kowalska, M. A.

D. Mas, M. A. Kowalska, J. Espinosa, and H. Kasprzak, “Custom design dynamic videokeratometer,” J. Mod. Opt. 57, 94–102 (2010).
[CrossRef]

Lam, A. K. C.

P. Cho, A. K. C. Lam, J. Mountford, and L. Ng, “The performance of four different corneal topographers on normal human corneas and its impact on orthokeratology lens fitting,” Optom. Vis. Sci. 79, 175–183 (2002).
[CrossRef]

Mas, D.

J. Espinosa, J. Pérez, D. Mas, and C. Illueca, “Weighted Zernike polynomial fitting in steep corneas sampled in Cartesian grid,” J. Mod. Opt. 58, 1710–1715 (2011).
[CrossRef]

D. Mas, M. A. Kowalska, J. Espinosa, and H. Kasprzak, “Custom design dynamic videokeratometer,” J. Mod. Opt. 57, 94–102 (2010).
[CrossRef]

Mountford, J.

P. Cho, A. K. C. Lam, J. Mountford, and L. Ng, “The performance of four different corneal topographers on normal human corneas and its impact on orthokeratology lens fitting,” Optom. Vis. Sci. 79, 175–183 (2002).
[CrossRef]

Ng, L.

P. Cho, A. K. C. Lam, J. Mountford, and L. Ng, “The performance of four different corneal topographers on normal human corneas and its impact on orthokeratology lens fitting,” Optom. Vis. Sci. 79, 175–183 (2002).
[CrossRef]

Ohashi, Y.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Pérez, J.

J. Espinosa, J. Pérez, D. Mas, and C. Illueca, “Weighted Zernike polynomial fitting in steep corneas sampled in Cartesian grid,” J. Mod. Opt. 58, 1710–1715 (2011).
[CrossRef]

Read, S. A.

S. A. Read, M. J. Collins, L. G. Carney, and R. J. Franklin, “The topography of the central and peripheral cornea,” Invest. Ophthalmol. Visual Sci. 47, 1404–1415 (2006).
[CrossRef]

Roberts, C.

C. Roberts, “Characterization of the inherent error in a spherically-biased corneal topography system in mapping a radially aspheric surface,” J. Refract. Corneal Surg. 10, 103–111 (1994).

Romao, A. C.

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

Schor, P.

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

Serra, J.

J. Serra, Image Analysis and Mathematical Morphology(Academic, 1983).

Tang, W.

W. Tang, M. J. Collins, L. Carney, and B. Davis, “The accuracy and precision performance of four videokeratoscopes in measuring test surfaces,” Optom. Vis. Sci. 77, 483–491 (2000).
[CrossRef]

Tatematsu, Y.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Tonissi, S.

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

Tsubota, K.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Uno, T.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Yasuoka, F.

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

Zheng, X.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Am. J. Ophthalmol.

T. Goto, X. Zheng, S. D. Klyce, H. Kataoka, T. Uno, M. Karon, Y. Tatematsu, T. Bessyo, K. Tsubota, and Y. Ohashi, “A new method for tear film stability analysis using videokeratography,” Am. J. Ophthalmol. 135, 607–612 (2003).
[CrossRef]

Arq. Bras. Oftalmol.

L. A. V. De Carvalho, A. C. Romao, S. Tonissi, F. Yasuoka, J. C. Castro, P. Schor, and W. Chamon, “Videokeratograph (VKS) for monitoring corneal curvature during surgery,” Arq. Bras. Oftalmol. 65, 37–41 (2002).
[CrossRef]

Clin. Exp. Optom.

D. R. Iskander and M. J. Collins, “Applications of high-speed videokeratoscopy,” Clin. Exp. Optom. 88, 399–407 (2004).
[CrossRef]

Invest. Ophthalmol. Visual Sci.

S. A. Read, M. J. Collins, L. G. Carney, and R. J. Franklin, “The topography of the central and peripheral cornea,” Invest. Ophthalmol. Visual Sci. 47, 1404–1415 (2006).
[CrossRef]

J. Mod. Opt.

D. Mas, M. A. Kowalska, J. Espinosa, and H. Kasprzak, “Custom design dynamic videokeratometer,” J. Mod. Opt. 57, 94–102 (2010).
[CrossRef]

J. Espinosa, J. Pérez, D. Mas, and C. Illueca, “Weighted Zernike polynomial fitting in steep corneas sampled in Cartesian grid,” J. Mod. Opt. 58, 1710–1715 (2011).
[CrossRef]

J. Refract. Corneal Surg.

C. Roberts, “Characterization of the inherent error in a spherically-biased corneal topography system in mapping a radially aspheric surface,” J. Refract. Corneal Surg. 10, 103–111 (1994).

Optom. Vis. Sci.

W. Tang, M. J. Collins, L. Carney, and B. Davis, “The accuracy and precision performance of four videokeratoscopes in measuring test surfaces,” Optom. Vis. Sci. 77, 483–491 (2000).
[CrossRef]

P. Cho, A. K. C. Lam, J. Mountford, and L. Ng, “The performance of four different corneal topographers on normal human corneas and its impact on orthokeratology lens fitting,” Optom. Vis. Sci. 79, 175–183 (2002).
[CrossRef]

Other

S. A. Klein, “Corneal topography: a review, new ANSI standards and problems to solve,” in Vision Science and its Applications, OSA Technical Digest (Optical Society of America, 2000), paper NW8.

J. Serra, Image Analysis and Mathematical Morphology(Academic, 1983).

Supplementary Material (1)

» Media 1: AVI (9235 KB)     

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Figures (8)

Fig. 1.
Fig. 1.

(a) Initial frame. (b) Open minus close top-hat filtered frame.

Fig. 2.
Fig. 2.

(a) Initial binarized frame. (b) Final-frame excerpts from video of the labeling of projected rings through the scanning annulus (Media 1).

Fig. 3.
Fig. 3.

Detected rings and edges obtained from the inner and outer perimeters of those which are not broken.

Fig. 4.
Fig. 4.

Slopes and ordinates at origin as a function of the labels.

Fig. 5.
Fig. 5.

Calibration surface obtained just taking into account the rings.

Fig. 6.
Fig. 6.

Mean curvature radii of the calibration spheres obtained both by our algorithm and Medmont.

Fig. 7.
Fig. 7.

Real samples using the posed method versus radial distance compared with those for a standard Cartesian sampling of 100mm2 and with constant radial sampling density provided by Medmont, in a Cartesian quadrant obtained for a real eye.

Fig. 8.
Fig. 8.

(a) Curvature radii from Medmont. (b) Obtained curvature radii.

Tables (2)

Tables Icon

Table 1. Parameters of the Calibration Surface Obtained from the Fitting to Eq. (4)

Tables Icon

Table 2. Parameter Coefficients for the Fitting Used to Check the Consistency of the Method

Equations (8)

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

FB=(FΘB)B,
F·B=(FB)ΘB,
OTHFB=(FFB),
CTHFB=(F·BF).
R=mlρ+nl,
R=plρ+qlR=pl(ρ+qp)R=pl(ρ+s),
ρ(x,y)=R(x,y)pl(x,y)s,
Δρ(x,y)=R(x,y)p2l(x,y)Δp+Δs.

Metrics