Abstract

We present measurements of water absorption in human cornea in vitro with a differential absorption optical coherence tomography (DAOCT) technique. This technique uses two OCT images recorded simultaneously with two different light sources, one centered within (1488nm) and one centered outside (1312nm) of a water absorption band. We investigated the cornea under different conditions: First, a series of OCT images were recorded at different hydration states of the cornea, starting from a normally hydrated cornea to an almost completely dehydrated cornea. To investigate the influence of scattering on our measurements, the dehydrated cornea was re-hydrated with Deuterium oxide, which shows similar optical properties like water, but negligible absorption in the used wavelength region, and a similar series of OCT images was recorded. For a quantitative analysis, we averaged the OCT signals over adjacent A-Scans and performed a linear regression analysis of the logarithmic OCT signals versus imaging depth in the cornea for each wavelength. The difference of the slopes corresponds to the difference in the absorption coefficient, if the difference in the scattering coefficient is negligible. With the known difference in the absorption cross section it is possible to calculate the mean water concentration of the cornea.

© 2003 Optical Society of America

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References

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  1. D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, �??Optical coherence tomography�?? Science 254, 1178-1181 (1991).
    [CrossRef] [PubMed]
  2. A. F. Fercher, C. K. Hitzenberger, W. Drexler, G. Kamp, H. Sattman, �??In vivo optical coherence tomography�?? Am. J. Ophthalmology 116, 113-114 (1993).
  3. W. Drexler, U. Morgner, R. K. Ghanta, F. X. Kaertner,J. S. Schuman, J. G. Fujimoto, �??Ultrahigh-resolution ophthalmic optical coherence tomography�?? Nature Med. 7, 502-507 (2001).
    [CrossRef] [PubMed]
  4. B. E. Bouma, G. J. Tearney, Handbook of Optical Coherence Tomography, (Marcel Dekker, New York 2002).
  5. A. F. Fercher, C. K. Hitzenberger, �??Optical coherence tomography, �??Chapter 4 in Progress in Optics 44, Elsevier Science B.V. (2002)
  6. A. F. Fercher, W. Drexler, C. K. Hitzenberger and T. Lasser, �??Optical coherence tomography- principles and application�?? Rep. Prog. Phys. 66. 239-303 (2003)
    [CrossRef]
  7. J. F. de Boer, T. E. Milner, M. J. C. van Gemert, J. S. Nelson, "Two-dimensional birefringence imaging in biological tissue by polarization sensitive optical coherence tomography" Opt. Lett. 22, 934-936 (1997).
    [CrossRef] [PubMed]
  8. S. Yazdanfar, A. M. Rollins, J. A. Izatt, �??Imaging and velocimetry of the human retinal circulation with color Doppler optical coherence tomography�?? Opt. Lett. 25, 1448-1450 (2000).
    [CrossRef]
  9. U. Morgner, W. Drexler, F. X. Kaertner, X. D. Li, C. Pitris, E. P. Ippen, J. G. Fujimoto, �??Spectroscopic optical coherence tomography�?? Opt. Lett. 25, 111-113 (2000)
    [CrossRef]
  10. G. M. Hale, M.R. Querry: �??Optical Constants of Water in the 200nm to 200m Wavelength Region�?? Appl. Opt. 12, 555-563 (1973)
    [CrossRef] [PubMed]
  11. J. M. Schmitt, S. H. Xiang, K. M. Yung �??Differential absorption imaging with optical coherence tomography�?? JOSA A, 15, 2288-2296 (1998)
    [CrossRef]
  12. U. S. Sathyam, B. W. Colston, Jr., L. B. Da Silva, and M. J. Everett �??Evaluation of optical coherence quantitation of analytes in turbid media by use of two wavelengths�?? Appl. Opt. 38, 2097-2104 (1999)
    [CrossRef]
  13. Y. Feng, J. Varikooty, T.L. Simpson: �??Diurnal Variation of Corneal and Corneal Epithelial Thickness Measured Using Optical Coherence Tomography�?? Cornea 20, 480-483 (2001)
    [CrossRef] [PubMed]
  14. J. M. Schmitt, S. L. Lee, K. M. Yung: �??An optical coherence microscope with enhanced resolving power in thick tissue�?? Opt. Commun. 142, 203-207 (1997)
    [CrossRef]
  15. H.E. Kaufmann, B.A. Barron, M.B. McDonald, "The Cornea" (Butterworth-Heinemann 1998)
  16. J. W. Goodman, "Statistical Optics" (John Wiley & Sons, Inc, New York 1985).
  17. M. Pircher, E. Götzinger, R. Leitgeb, A. F. Fercher and C. K. Hitzenberger, �??Speckle reduction in optical coherence tomography by frequency compounding�?? J. Biomed. Opt. 8 (3) (2003).
    [CrossRef] [PubMed]

Am. J. Ophthalmology

A. F. Fercher, C. K. Hitzenberger, W. Drexler, G. Kamp, H. Sattman, �??In vivo optical coherence tomography�?? Am. J. Ophthalmology 116, 113-114 (1993).

Appl. Opt.

Cornea

Y. Feng, J. Varikooty, T.L. Simpson: �??Diurnal Variation of Corneal and Corneal Epithelial Thickness Measured Using Optical Coherence Tomography�?? Cornea 20, 480-483 (2001)
[CrossRef] [PubMed]

J. Biomed. Opt.

M. Pircher, E. Götzinger, R. Leitgeb, A. F. Fercher and C. K. Hitzenberger, �??Speckle reduction in optical coherence tomography by frequency compounding�?? J. Biomed. Opt. 8 (3) (2003).
[CrossRef] [PubMed]

JOSA A

J. M. Schmitt, S. H. Xiang, K. M. Yung �??Differential absorption imaging with optical coherence tomography�?? JOSA A, 15, 2288-2296 (1998)
[CrossRef]

Nature Med.

W. Drexler, U. Morgner, R. K. Ghanta, F. X. Kaertner,J. S. Schuman, J. G. Fujimoto, �??Ultrahigh-resolution ophthalmic optical coherence tomography�?? Nature Med. 7, 502-507 (2001).
[CrossRef] [PubMed]

Opt. Commun.

J. M. Schmitt, S. L. Lee, K. M. Yung: �??An optical coherence microscope with enhanced resolving power in thick tissue�?? Opt. Commun. 142, 203-207 (1997)
[CrossRef]

Opt. Lett.

Progress in Optics

A. F. Fercher, C. K. Hitzenberger, �??Optical coherence tomography, �??Chapter 4 in Progress in Optics 44, Elsevier Science B.V. (2002)

Rep. Prog. Phys.

A. F. Fercher, W. Drexler, C. K. Hitzenberger and T. Lasser, �??Optical coherence tomography- principles and application�?? Rep. Prog. Phys. 66. 239-303 (2003)
[CrossRef]

Other

B. E. Bouma, G. J. Tearney, Handbook of Optical Coherence Tomography, (Marcel Dekker, New York 2002).

H.E. Kaufmann, B.A. Barron, M.B. McDonald, "The Cornea" (Butterworth-Heinemann 1998)

J. W. Goodman, "Statistical Optics" (John Wiley & Sons, Inc, New York 1985).

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, �??Optical coherence tomography�?? Science 254, 1178-1181 (1991).
[CrossRef] [PubMed]

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Figures (7)

Fig. 1.
Fig. 1.

Experimental setup of the differential absorption OCT technique. SLD…Superluminescent diodes, WDM…wavelength division multiplexer, NPBS…non polarizing beam splitter, BS beam splitter, D1, D2, D3…detectors.

Fig. 2.
Fig. 2.

OCT images of a human cornea in vitro a) intensity image recorded at 1312nm; b) intensity image recorded at 1488nm; c) Floating average of the difference between a) and b) (differential intensity image).

Fig. 3.
Fig. 3.

OCT images of a human cornea in vitro after swelling with Deuterium oxide a) intensity image recorded at 1312nm; b) intensity image recorded at 1488nm; c) calculated differential intensity image.

Fig. 4.
Fig. 4.

(676kB) Movie of time series (80 min.) of the calculated differential intensity image of the cornea containing H2O (upper image) and the cornea containing D2O (lower image).

Fig. 5.
Fig. 5.

Plot of the averaged logarithmic intensities with depth: a) cornea containing water, b) cornea containing Deuterium oxide, black… 1312nm, red… 1488nm.

Fig. 6.
Fig. 6.

Variation of water concentration (hydration) of a human cornea in vitro with time. Solid line…hydration calculated from the thickness of the cornea, dots…measured hydration with the differential absorption OCT technique.

Fig. 7.
Fig. 7.

Error analysis of the differential absorption OCT technique. Solid line…hydration calculated from the thickness of the cornea, dots…measured hydration with the differential absorption OCT technique.

Equations (11)

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

I ( λ , d ) = I 0 ( λ ) e ( μ a ( λ ) + μ s ( λ ) ) d ,
S OCT ( z ) = K I r I s ( z ) .
ln ( S OCT ( z ) ) = ln ( K I r I 0 ) ( μ a + μ s ) z ,
ln ( S OCT ( z , λ 1 ) ) ln ( S OCT ( z , λ 2 ) ) = ln ( I r ( λ 1 ) I 0 ( λ 1 ) I r ( λ 2 ) I 0 ( λ 2 ) ) ( Δ μ a + Δ μ s ) z ,
ln ( S OCT ( z , λ 1 ) S OCT ( z , λ 2 ) ) = Const . ( Δ μ a + Δ μ s ) z .
k = ( Δ μ a + Δ μ s ) .
c = Δ μ a Δ σ a .
K = σ A ¯ ,
S k 2 = S y 2 N N x i 2 ( x i ) 2 ,
N = x tot l c ,
S c c = S k Δ μ a ,

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