Video Abstract
Quantitative OCT-based corneal topography in keratoconus with intracorneal ring segments

Abstract

Custom high-resolution high-speed anterior segment spectral domain Optical Coherence Tomography (OCT) was used to characterize three-dimensionally (3-D) corneal topography in keratoconus before and after implantation of intracorneal ring segments (ICRS). Previously described acquisition protocols were followed to minimize the impact of the motions of the eye. The collected set of images was corrected from distortions: fan (scanning) and optical (refraction). Custom algorithms were developed for automatic detection and classification of volumes in the anterior segment of the eye, in particular for the detection and classification of the implanted ICRS. Surfaces were automatically detected for quantitative analysis of the corneal elevation maps (fitted by biconicoids and Zernike polynomials) and pachymetry. Automatic tools were developed for the estimation of the 3-D positioning of the ICRS. The pupil center reference was estimated from the segmented iris volume. The developed algorithms are illustrated in a keratoconic eye (grade III) pre- and 30 days post-operatively after implantation of two triangular-section, 0.3-mm thick Ferrara ring segments. Quantitative corneal topographies reveal that the ICRS produced a flattening of the anterior surface, a steepening of the posterior surface, meridional differences in the changes in curvature and asphericity, and increased symmetry of the anterior topography. Optical distortion correction through the ICRS (of a different refractive index from the cornea) allowed accurate pachymetric estimates, which showed increased thickness in the ectatic area as well as in peripheral corneal areas. Automatic tools allowed estimation of the depth of the implanted ICRS ring, as well as its rotation with respect to the pupil plane. Anterior segment sOCT provided with fan and optical distortion correction and analysis tools is an excellent instrument for evaluating and monitoring keratoconic eyes and for the quantification of the changes produced by ICRS treatment.

© 2012 OSA

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2011 (4)

H. L. Rao, A. U. Kumar, A. Kumar, S. Chary, S. Senthil, P. K. Vaddavalli, and C. S. Garudadri, “Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects,” Cornea30(2), 121–126 (2011).
[CrossRef] [PubMed]

A. Ishibazawa, S. Igarashi, K. Hanada, T. Nagaoka, S. Ishiko, H. Ito, and A. Yoshida, “Central corneal thickness measurements with Fourier-domain optical coherence tomography versus ultrasonic pachymetry and rotating Scheimpflug camera,” Cornea30(6), 615–619 (2011).
[CrossRef] [PubMed]

S. Ortiz, D. Siedlecki, P. Pérez-Merino, N. Chia, A. de Castro, M. Szkulmowski, M. Wojtkowski, and S. Marcos, “Corneal topography from spectral optical coherence tomography (sOCT),” Biomed. Opt. Express2(12), 3232–3247 (2011).
[CrossRef] [PubMed]

K. Karnowski, B. J. Kaluzny, M. Szkulmowski, M. Gora, and M. Wojtkowski, “Corneal topography with high-speed swept source OCT in clinical examination,” Biomed. Opt. Express2(9), 2709–2720 (2011).
[CrossRef] [PubMed]

2010 (5)

2009 (7)

C. Dauwe, D. Touboul, C. J. Roberts, A. M. Mahmoud, J. Kérautret, P. Fournier, F. Malecaze, and J. Colin, “Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus,” J. Cataract Refract. Surg.35(10), 1761–1767 (2009).
[CrossRef] [PubMed]

G. Kamburoglu, A. Ertan, and O. Saraçbasi, “Measurement of depth of Intacs implanted via femtosecond laser using Pentacam,” J. Refract. Surg.25(4), 377–382 (2009).
[CrossRef] [PubMed]

S. Ortiz, D. Siedlecki, L. Remon, and S. Marcos, “Optical coherence tomography for quantitative surface topography,” Appl. Opt.48(35), 6708–6715 (2009).
[CrossRef] [PubMed]

S. Ortiz, D. Siedlecki, L. Remon, and S. Marcos, “Three-dimensional ray tracing on Delaunay-based reconstructed surfaces,” Appl. Opt.48(20), 3886–3893 (2009).
[CrossRef] [PubMed]

S. A. Read, M. J. Collins, D. R. Iskander, and B. A. Davis, “Corneal topography with Scheimpflug imaging and videokeratography: comparative study of normal eyes,” J. Cataract Refract. Surg.35(6), 1072–1081 (2009).
[CrossRef] [PubMed]

A. Pérez-Escudero, C. Dorronsoro, L. Sawides, L. Remón, J. Merayo-Lloves, and S. Marcos, “Minor influence of myopic laser in situ keratomileusis on the posterior corneal surface,” Invest. Ophthalmol. Vis. Sci.50(9), 4146–4154 (2009).
[CrossRef] [PubMed]

I. Grulkowski, M. Gora, M. Szkulmowski, I. Gorczynska, D. Szlag, S. Marcos, A. Kowalczyk, and M. Wojtkowski, “Anterior segment imaging with Spectral OCT system using a high-speed CMOS camera,” Opt. Express17(6), 4842–4858 (2009).
[CrossRef] [PubMed]

2008 (3)

Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
[CrossRef] [PubMed]

H. Shankar, D. Taranath, C. T. Santhirathelagan, and K. Pesudovs, “Repeatability of corneal first-surface wavefront aberrations measured with Pentacam corneal topography,” J. Cataract Refract. Surg.34(5), 727–734 (2008).
[CrossRef] [PubMed]

S. M. Kymes, J. J. Walline, K. Zadnik, J. Sterling, M. O. Gordon, and Collaborative Longitudinal Evaluation of Keratoconus Study Group, “Changes in the quality-of-life of people with keratoconus,” Am. J. Ophthalmol.145(4), 611–617.e1 (2008).
[CrossRef] [PubMed]

2007 (1)

U. de Sanctis, A. Missolungi, B. Mutani, L. Richiardi, and F. M. Grignolo, “Reproducibility and repeatability of central corneal thickness measurement in keratoconus using the rotating Scheimpflug camera and ultrasound pachymetry,” Am. J. Ophthalmol.144(5), 712–718.e1 (2007).
[CrossRef] [PubMed]

2006 (1)

M. M. Lai, M. Tang, E. M. Andrade, Y. Li, R. N. Khurana, J. C. Song, and D. Huang, “Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes,” J. Cataract Refract. Surg.32(11), 1860–1865 (2006).
[CrossRef] [PubMed]

2005 (2)

K. Kawana, K. Miyata, T. Tokunaga, T. Kiuchi, T. Hiraoka, and T. Oshika, “Central corneal thickness measurements using Orbscan II scanning slit topography, noncontact specular microscopy, and ultrasonic pachymetry in eyes with keratoconus,” Cornea24(8), 967–971 (2005).
[CrossRef] [PubMed]

M. A. Javadi, B. F. Motlagh, M. R. Jafarinasab, Z. Rabbanikhah, A. Anissian, H. Souri, and S. Yazdani, “Outcomes of penetrating keratoplasty in keratoconus,” Cornea24(8), 941–946 (2005).
[CrossRef] [PubMed]

2003 (1)

G. Wollensak, E. Spoerl, and T. Seiler, “Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus,” Am. J. Ophthalmol.135(5), 620–627 (2003).
[CrossRef] [PubMed]

2002 (4)

D. Siganos, P. Ferrara, K. Chatzinikolas, N. Bessis, and G. Papastergiou, “Ferrara intrastromal corneal rings for the correction of keratoconus,” J. Cataract Refract. Surg.28(11), 1947–1951 (2002).
[CrossRef] [PubMed]

J. L. Alió, T. F. Salem, A. Artola, and A. A. Osman, “Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis,” J. Cataract Refract. Surg.28(9), 1568–1574 (2002).
[CrossRef] [PubMed]

S. Barbero, S. Marcos, J. Merayo-Lloves, and E. Moreno-Barriuso, “Validation of the estimation of corneal aberrations from videokeratography in keratoconus,” J. Refract. Surg.18(3), 263–270 (2002).
[PubMed]

Y. Yang, K. Thompson, and S. A. Burns, “Pupil location under mesopic, photopic, and pharmacologically dilated conditions,” Invest. Ophthalmol. Vis. Sci.43(7), 2508–2512 (2002).
[PubMed]

2001 (1)

D. Z. Reinstein, S. Srivannaboon, and S. P. Holland, “Epithelial and stromal changes induced by intacs examined by three-dimensional very high-frequency digital ultrasound,” J. Refract. Surg.17(3), 310–318 (2001).
[PubMed]

2000 (2)

J. Colin, B. Cochener, G. Savary, and F. Malet, “Correcting keratoconus with intracorneal rings,” J. Cataract Refract. Surg.26(8), 1117–1122 (2000).
[CrossRef] [PubMed]

A. Tomidokoro, T. Oshika, S. Amano, S. Higaki, N. Maeda, and K. Miyata, “Changes in anterior and posterior corneal curvatures in keratoconus,” Ophthalmology107(7), 1328–1332 (2000).
[CrossRef] [PubMed]

1998 (2)

Y. S. Rabinowitz, “Keratoconus,” Surv. Ophthalmol.42(4), 297–319 (1998).
[CrossRef] [PubMed]

T. E. Burris, “Intrastromal corneal ring technology: results and indications,” Curr. Opin. Ophthalmol.9(4), 9–14 (1998).
[CrossRef] [PubMed]

1997 (1)

L. T. Nordan, “Keratoconus: diagnosis and treatment,” Int. Ophthalmol. Clin.37(1), 51–63 (1997).
[CrossRef] [PubMed]

1994 (1)

N. Maeda, S. D. Klyce, M. K. Smolek, and H. W. Thompson, “Automated keratoconus screening with corneal topography analysis,” Invest. Ophthalmol. Vis. Sci.35(6), 2749–2757 (1994).
[PubMed]

1993 (1)

T. E. Burris, P. C. Baker, C. T. Ayer, B. E. Loomas, M. L. Mathis, and T. A. Silvestrini, “Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study,” J. Cataract Refract. Surg.19(Suppl), 182–187 (1993).
[PubMed]

1992 (1)

N. Mamalis, C. W. Anderson, K. R. Kreisler, M. K. Lundergan, and R. J. Olson, “Changing trends in the indications for penetrating keratoplasty,” Arch. Ophthalmol.110(10), 1409–1411 (1992).
[CrossRef] [PubMed]

1989 (2)

L. J. Maguire and W. M. Bourne, “Corneal topography of early keratoconus,” Am. J. Ophthalmol.108(2), 107–112 (1989).
[PubMed]

Y. S. Rabinowitz and P. J. McDonnell, “Computer-assisted corneal topography in keratoconus,” Refract. Corneal Surg.5(6), 400–408 (1989).
[PubMed]

1988 (1)

1968 (1)

E. D. Blavatskaya, “Intralamellar homoplasty for the purpose of relaxation of refraction of the eye,” Arch. Soc. Am. Ophthalmol. Optom.6, 311–325 (1968).

1966 (1)

J. I. Barraquer, “Modification of refraction by means of intracorneal inclusions,” Int. Ophthalmol. Clin.6(1), 53–78 (1966).
[PubMed]

Alio, J. L.

D. P. Piñero, J. L. Alio, M. A. Teus, R. I. Barraquer, and A. Uceda-Montañés, “Modeling the intracorneal ring segment effect in keratoconus using refractive, keratometric, and corneal aberrometric data,” Invest. Ophthalmol. Vis. Sci.51(11), 5583–5591 (2010).
[CrossRef] [PubMed]

Alió, J. L.

J. L. Alió, T. F. Salem, A. Artola, and A. A. Osman, “Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis,” J. Cataract Refract. Surg.28(9), 1568–1574 (2002).
[CrossRef] [PubMed]

Amano, S.

A. Tomidokoro, T. Oshika, S. Amano, S. Higaki, N. Maeda, and K. Miyata, “Changes in anterior and posterior corneal curvatures in keratoconus,” Ophthalmology107(7), 1328–1332 (2000).
[CrossRef] [PubMed]

Anderson, C. W.

N. Mamalis, C. W. Anderson, K. R. Kreisler, M. K. Lundergan, and R. J. Olson, “Changing trends in the indications for penetrating keratoplasty,” Arch. Ophthalmol.110(10), 1409–1411 (1992).
[CrossRef] [PubMed]

Andrade, E. M.

M. M. Lai, M. Tang, E. M. Andrade, Y. Li, R. N. Khurana, J. C. Song, and D. Huang, “Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes,” J. Cataract Refract. Surg.32(11), 1860–1865 (2006).
[CrossRef] [PubMed]

Anissian, A.

M. A. Javadi, B. F. Motlagh, M. R. Jafarinasab, Z. Rabbanikhah, A. Anissian, H. Souri, and S. Yazdani, “Outcomes of penetrating keratoplasty in keratoconus,” Cornea24(8), 941–946 (2005).
[CrossRef] [PubMed]

Arffa, R. C.

Artola, A.

J. L. Alió, T. F. Salem, A. Artola, and A. A. Osman, “Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis,” J. Cataract Refract. Surg.28(9), 1568–1574 (2002).
[CrossRef] [PubMed]

Ayer, C. T.

T. E. Burris, P. C. Baker, C. T. Ayer, B. E. Loomas, M. L. Mathis, and T. A. Silvestrini, “Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study,” J. Cataract Refract. Surg.19(Suppl), 182–187 (1993).
[PubMed]

Baker, P. C.

T. E. Burris, P. C. Baker, C. T. Ayer, B. E. Loomas, M. L. Mathis, and T. A. Silvestrini, “Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study,” J. Cataract Refract. Surg.19(Suppl), 182–187 (1993).
[PubMed]

Barbero, S.

S. Barbero, S. Marcos, J. Merayo-Lloves, and E. Moreno-Barriuso, “Validation of the estimation of corneal aberrations from videokeratography in keratoconus,” J. Refract. Surg.18(3), 263–270 (2002).
[PubMed]

Barraquer, J. I.

J. I. Barraquer, “Modification of refraction by means of intracorneal inclusions,” Int. Ophthalmol. Clin.6(1), 53–78 (1966).
[PubMed]

Barraquer, R. I.

D. P. Piñero, J. L. Alio, M. A. Teus, R. I. Barraquer, and A. Uceda-Montañés, “Modeling the intracorneal ring segment effect in keratoconus using refractive, keratometric, and corneal aberrometric data,” Invest. Ophthalmol. Vis. Sci.51(11), 5583–5591 (2010).
[CrossRef] [PubMed]

Bessis, N.

D. Siganos, P. Ferrara, K. Chatzinikolas, N. Bessis, and G. Papastergiou, “Ferrara intrastromal corneal rings for the correction of keratoconus,” J. Cataract Refract. Surg.28(11), 1947–1951 (2002).
[CrossRef] [PubMed]

Blavatskaya, E. D.

E. D. Blavatskaya, “Intralamellar homoplasty for the purpose of relaxation of refraction of the eye,” Arch. Soc. Am. Ophthalmol. Optom.6, 311–325 (1968).

Bourne, W. M.

L. J. Maguire and W. M. Bourne, “Corneal topography of early keratoconus,” Am. J. Ophthalmol.108(2), 107–112 (1989).
[PubMed]

Burns, S. A.

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A. Pérez-Escudero, C. Dorronsoro, and S. Marcos, “Correlation between radius and asphericity in surfaces fitted by conics,” J. Opt. Soc. Am. A27(7), 1541–1548 (2010).
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A. Pérez-Escudero, C. Dorronsoro, L. Sawides, L. Remón, J. Merayo-Lloves, and S. Marcos, “Minor influence of myopic laser in situ keratomileusis on the posterior corneal surface,” Invest. Ophthalmol. Vis. Sci.50(9), 4146–4154 (2009).
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G. Kamburoglu, A. Ertan, and O. Saraçbasi, “Measurement of depth of Intacs implanted via femtosecond laser using Pentacam,” J. Refract. Surg.25(4), 377–382 (2009).
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Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
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S. A. Read, M. J. Collins, D. R. Iskander, and B. A. Davis, “Corneal topography with Scheimpflug imaging and videokeratography: comparative study of normal eyes,” J. Cataract Refract. Surg.35(6), 1072–1081 (2009).
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Jafarinasab, M. R.

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Kaluzny, B. J.

Kamburoglu, G.

G. Kamburoglu, A. Ertan, and O. Saraçbasi, “Measurement of depth of Intacs implanted via femtosecond laser using Pentacam,” J. Refract. Surg.25(4), 377–382 (2009).
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K. Kawana, K. Miyata, T. Tokunaga, T. Kiuchi, T. Hiraoka, and T. Oshika, “Central corneal thickness measurements using Orbscan II scanning slit topography, noncontact specular microscopy, and ultrasonic pachymetry in eyes with keratoconus,” Cornea24(8), 967–971 (2005).
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C. Dauwe, D. Touboul, C. J. Roberts, A. M. Mahmoud, J. Kérautret, P. Fournier, F. Malecaze, and J. Colin, “Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus,” J. Cataract Refract. Surg.35(10), 1761–1767 (2009).
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M. M. Lai, M. Tang, E. M. Andrade, Y. Li, R. N. Khurana, J. C. Song, and D. Huang, “Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes,” J. Cataract Refract. Surg.32(11), 1860–1865 (2006).
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H. L. Rao, A. U. Kumar, A. Kumar, S. Chary, S. Senthil, P. K. Vaddavalli, and C. S. Garudadri, “Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects,” Cornea30(2), 121–126 (2011).
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H. L. Rao, A. U. Kumar, A. Kumar, S. Chary, S. Senthil, P. K. Vaddavalli, and C. S. Garudadri, “Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects,” Cornea30(2), 121–126 (2011).
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M. M. Lai, M. Tang, E. M. Andrade, Y. Li, R. N. Khurana, J. C. Song, and D. Huang, “Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes,” J. Cataract Refract. Surg.32(11), 1860–1865 (2006).
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Y. Li, M. Tang, X. Zhang, C. H. Salaroli, J. L. Ramos, and D. Huang, “Pachymetric mapping with Fourier-domain optical coherence tomography,” J. Cataract Refract. Surg.36(5), 826–831 (2010).
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Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
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M. M. Lai, M. Tang, E. M. Andrade, Y. Li, R. N. Khurana, J. C. Song, and D. Huang, “Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes,” J. Cataract Refract. Surg.32(11), 1860–1865 (2006).
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T. E. Burris, P. C. Baker, C. T. Ayer, B. E. Loomas, M. L. Mathis, and T. A. Silvestrini, “Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study,” J. Cataract Refract. Surg.19(Suppl), 182–187 (1993).
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Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
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N. Mamalis, C. W. Anderson, K. R. Kreisler, M. K. Lundergan, and R. J. Olson, “Changing trends in the indications for penetrating keratoplasty,” Arch. Ophthalmol.110(10), 1409–1411 (1992).
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A. Tomidokoro, T. Oshika, S. Amano, S. Higaki, N. Maeda, and K. Miyata, “Changes in anterior and posterior corneal curvatures in keratoconus,” Ophthalmology107(7), 1328–1332 (2000).
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N. Maeda, S. D. Klyce, M. K. Smolek, and H. W. Thompson, “Automated keratoconus screening with corneal topography analysis,” Invest. Ophthalmol. Vis. Sci.35(6), 2749–2757 (1994).
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C. Dauwe, D. Touboul, C. J. Roberts, A. M. Mahmoud, J. Kérautret, P. Fournier, F. Malecaze, and J. Colin, “Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus,” J. Cataract Refract. Surg.35(10), 1761–1767 (2009).
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C. Dauwe, D. Touboul, C. J. Roberts, A. M. Mahmoud, J. Kérautret, P. Fournier, F. Malecaze, and J. Colin, “Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus,” J. Cataract Refract. Surg.35(10), 1761–1767 (2009).
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J. Colin, B. Cochener, G. Savary, and F. Malet, “Correcting keratoconus with intracorneal rings,” J. Cataract Refract. Surg.26(8), 1117–1122 (2000).
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N. Mamalis, C. W. Anderson, K. R. Kreisler, M. K. Lundergan, and R. J. Olson, “Changing trends in the indications for penetrating keratoplasty,” Arch. Ophthalmol.110(10), 1409–1411 (1992).
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A. Pérez-Escudero, C. Dorronsoro, and S. Marcos, “Correlation between radius and asphericity in surfaces fitted by conics,” J. Opt. Soc. Am. A27(7), 1541–1548 (2010).
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S. Ortiz, D. Siedlecki, I. Grulkowski, L. Remon, D. Pascual, M. Wojtkowski, and S. Marcos, “Optical distortion correction in optical coherence tomography for quantitative ocular anterior segment by three-dimensional imaging,” Opt. Express18(3), 2782–2796 (2010).
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I. Grulkowski, M. Gora, M. Szkulmowski, I. Gorczynska, D. Szlag, S. Marcos, A. Kowalczyk, and M. Wojtkowski, “Anterior segment imaging with Spectral OCT system using a high-speed CMOS camera,” Opt. Express17(6), 4842–4858 (2009).
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S. Ortiz, D. Siedlecki, L. Remon, and S. Marcos, “Optical coherence tomography for quantitative surface topography,” Appl. Opt.48(35), 6708–6715 (2009).
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A. Pérez-Escudero, C. Dorronsoro, L. Sawides, L. Remón, J. Merayo-Lloves, and S. Marcos, “Minor influence of myopic laser in situ keratomileusis on the posterior corneal surface,” Invest. Ophthalmol. Vis. Sci.50(9), 4146–4154 (2009).
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S. Barbero, S. Marcos, J. Merayo-Lloves, and E. Moreno-Barriuso, “Validation of the estimation of corneal aberrations from videokeratography in keratoconus,” J. Refract. Surg.18(3), 263–270 (2002).
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Mathis, M. L.

T. E. Burris, P. C. Baker, C. T. Ayer, B. E. Loomas, M. L. Mathis, and T. A. Silvestrini, “Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study,” J. Cataract Refract. Surg.19(Suppl), 182–187 (1993).
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Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
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Merayo-Lloves, J.

A. Pérez-Escudero, C. Dorronsoro, L. Sawides, L. Remón, J. Merayo-Lloves, and S. Marcos, “Minor influence of myopic laser in situ keratomileusis on the posterior corneal surface,” Invest. Ophthalmol. Vis. Sci.50(9), 4146–4154 (2009).
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S. Barbero, S. Marcos, J. Merayo-Lloves, and E. Moreno-Barriuso, “Validation of the estimation of corneal aberrations from videokeratography in keratoconus,” J. Refract. Surg.18(3), 263–270 (2002).
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U. de Sanctis, A. Missolungi, B. Mutani, L. Richiardi, and F. M. Grignolo, “Reproducibility and repeatability of central corneal thickness measurement in keratoconus using the rotating Scheimpflug camera and ultrasound pachymetry,” Am. J. Ophthalmol.144(5), 712–718.e1 (2007).
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K. Kawana, K. Miyata, T. Tokunaga, T. Kiuchi, T. Hiraoka, and T. Oshika, “Central corneal thickness measurements using Orbscan II scanning slit topography, noncontact specular microscopy, and ultrasonic pachymetry in eyes with keratoconus,” Cornea24(8), 967–971 (2005).
[CrossRef] [PubMed]

A. Tomidokoro, T. Oshika, S. Amano, S. Higaki, N. Maeda, and K. Miyata, “Changes in anterior and posterior corneal curvatures in keratoconus,” Ophthalmology107(7), 1328–1332 (2000).
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Moreno-Barriuso, E.

S. Barbero, S. Marcos, J. Merayo-Lloves, and E. Moreno-Barriuso, “Validation of the estimation of corneal aberrations from videokeratography in keratoconus,” J. Refract. Surg.18(3), 263–270 (2002).
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M. A. Javadi, B. F. Motlagh, M. R. Jafarinasab, Z. Rabbanikhah, A. Anissian, H. Souri, and S. Yazdani, “Outcomes of penetrating keratoplasty in keratoconus,” Cornea24(8), 941–946 (2005).
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U. de Sanctis, A. Missolungi, B. Mutani, L. Richiardi, and F. M. Grignolo, “Reproducibility and repeatability of central corneal thickness measurement in keratoconus using the rotating Scheimpflug camera and ultrasound pachymetry,” Am. J. Ophthalmol.144(5), 712–718.e1 (2007).
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A. Ishibazawa, S. Igarashi, K. Hanada, T. Nagaoka, S. Ishiko, H. Ito, and A. Yoshida, “Central corneal thickness measurements with Fourier-domain optical coherence tomography versus ultrasonic pachymetry and rotating Scheimpflug camera,” Cornea30(6), 615–619 (2011).
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N. Mamalis, C. W. Anderson, K. R. Kreisler, M. K. Lundergan, and R. J. Olson, “Changing trends in the indications for penetrating keratoplasty,” Arch. Ophthalmol.110(10), 1409–1411 (1992).
[CrossRef] [PubMed]

Ortiz, S.

Oshika, T.

K. Kawana, K. Miyata, T. Tokunaga, T. Kiuchi, T. Hiraoka, and T. Oshika, “Central corneal thickness measurements using Orbscan II scanning slit topography, noncontact specular microscopy, and ultrasonic pachymetry in eyes with keratoconus,” Cornea24(8), 967–971 (2005).
[CrossRef] [PubMed]

A. Tomidokoro, T. Oshika, S. Amano, S. Higaki, N. Maeda, and K. Miyata, “Changes in anterior and posterior corneal curvatures in keratoconus,” Ophthalmology107(7), 1328–1332 (2000).
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D. Siganos, P. Ferrara, K. Chatzinikolas, N. Bessis, and G. Papastergiou, “Ferrara intrastromal corneal rings for the correction of keratoconus,” J. Cataract Refract. Surg.28(11), 1947–1951 (2002).
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Pascual, D.

Pérez-Escudero, A.

A. Pérez-Escudero, C. Dorronsoro, and S. Marcos, “Correlation between radius and asphericity in surfaces fitted by conics,” J. Opt. Soc. Am. A27(7), 1541–1548 (2010).
[CrossRef] [PubMed]

A. Pérez-Escudero, C. Dorronsoro, L. Sawides, L. Remón, J. Merayo-Lloves, and S. Marcos, “Minor influence of myopic laser in situ keratomileusis on the posterior corneal surface,” Invest. Ophthalmol. Vis. Sci.50(9), 4146–4154 (2009).
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Pérez-Merino, P.

Pesudovs, K.

H. Shankar, D. Taranath, C. T. Santhirathelagan, and K. Pesudovs, “Repeatability of corneal first-surface wavefront aberrations measured with Pentacam corneal topography,” J. Cataract Refract. Surg.34(5), 727–734 (2008).
[CrossRef] [PubMed]

Piñero, D. P.

D. P. Piñero, J. L. Alio, M. A. Teus, R. I. Barraquer, and A. Uceda-Montañés, “Modeling the intracorneal ring segment effect in keratoconus using refractive, keratometric, and corneal aberrometric data,” Invest. Ophthalmol. Vis. Sci.51(11), 5583–5591 (2010).
[CrossRef] [PubMed]

Rabbanikhah, Z.

M. A. Javadi, B. F. Motlagh, M. R. Jafarinasab, Z. Rabbanikhah, A. Anissian, H. Souri, and S. Yazdani, “Outcomes of penetrating keratoplasty in keratoconus,” Cornea24(8), 941–946 (2005).
[CrossRef] [PubMed]

Rabinowitz, Y. S.

Y. S. Rabinowitz, “Keratoconus,” Surv. Ophthalmol.42(4), 297–319 (1998).
[CrossRef] [PubMed]

Y. S. Rabinowitz and P. J. McDonnell, “Computer-assisted corneal topography in keratoconus,” Refract. Corneal Surg.5(6), 400–408 (1989).
[PubMed]

Ramos, J. L.

Y. Li, M. Tang, X. Zhang, C. H. Salaroli, J. L. Ramos, and D. Huang, “Pachymetric mapping with Fourier-domain optical coherence tomography,” J. Cataract Refract. Surg.36(5), 826–831 (2010).
[CrossRef] [PubMed]

Rao, H. L.

H. L. Rao, A. U. Kumar, A. Kumar, S. Chary, S. Senthil, P. K. Vaddavalli, and C. S. Garudadri, “Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects,” Cornea30(2), 121–126 (2011).
[CrossRef] [PubMed]

Read, S. A.

S. A. Read, M. J. Collins, D. R. Iskander, and B. A. Davis, “Corneal topography with Scheimpflug imaging and videokeratography: comparative study of normal eyes,” J. Cataract Refract. Surg.35(6), 1072–1081 (2009).
[CrossRef] [PubMed]

Rehkopf, P. G.

Reinstein, D. Z.

D. Z. Reinstein, S. Srivannaboon, and S. P. Holland, “Epithelial and stromal changes induced by intacs examined by three-dimensional very high-frequency digital ultrasound,” J. Refract. Surg.17(3), 310–318 (2001).
[PubMed]

Reiser, B. J.

Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
[CrossRef] [PubMed]

Remon, L.

Remón, L.

A. Pérez-Escudero, C. Dorronsoro, L. Sawides, L. Remón, J. Merayo-Lloves, and S. Marcos, “Minor influence of myopic laser in situ keratomileusis on the posterior corneal surface,” Invest. Ophthalmol. Vis. Sci.50(9), 4146–4154 (2009).
[CrossRef] [PubMed]

Richiardi, L.

U. de Sanctis, A. Missolungi, B. Mutani, L. Richiardi, and F. M. Grignolo, “Reproducibility and repeatability of central corneal thickness measurement in keratoconus using the rotating Scheimpflug camera and ultrasound pachymetry,” Am. J. Ophthalmol.144(5), 712–718.e1 (2007).
[CrossRef] [PubMed]

Roberts, C. J.

C. Dauwe, D. Touboul, C. J. Roberts, A. M. Mahmoud, J. Kérautret, P. Fournier, F. Malecaze, and J. Colin, “Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus,” J. Cataract Refract. Surg.35(10), 1761–1767 (2009).
[CrossRef] [PubMed]

Salaroli, C. H.

Y. Li, M. Tang, X. Zhang, C. H. Salaroli, J. L. Ramos, and D. Huang, “Pachymetric mapping with Fourier-domain optical coherence tomography,” J. Cataract Refract. Surg.36(5), 826–831 (2010).
[CrossRef] [PubMed]

Salem, T. F.

J. L. Alió, T. F. Salem, A. Artola, and A. A. Osman, “Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis,” J. Cataract Refract. Surg.28(9), 1568–1574 (2002).
[CrossRef] [PubMed]

Santhirathelagan, C. T.

H. Shankar, D. Taranath, C. T. Santhirathelagan, and K. Pesudovs, “Repeatability of corneal first-surface wavefront aberrations measured with Pentacam corneal topography,” J. Cataract Refract. Surg.34(5), 727–734 (2008).
[CrossRef] [PubMed]

Saraçbasi, O.

G. Kamburoglu, A. Ertan, and O. Saraçbasi, “Measurement of depth of Intacs implanted via femtosecond laser using Pentacam,” J. Refract. Surg.25(4), 377–382 (2009).
[CrossRef] [PubMed]

Savary, G.

J. Colin, B. Cochener, G. Savary, and F. Malet, “Correcting keratoconus with intracorneal rings,” J. Cataract Refract. Surg.26(8), 1117–1122 (2000).
[CrossRef] [PubMed]

Sawides, L.

A. Pérez-Escudero, C. Dorronsoro, L. Sawides, L. Remón, J. Merayo-Lloves, and S. Marcos, “Minor influence of myopic laser in situ keratomileusis on the posterior corneal surface,” Invest. Ophthalmol. Vis. Sci.50(9), 4146–4154 (2009).
[CrossRef] [PubMed]

Seiler, T.

G. Wollensak, E. Spoerl, and T. Seiler, “Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus,” Am. J. Ophthalmol.135(5), 620–627 (2003).
[CrossRef] [PubMed]

Senthil, S.

H. L. Rao, A. U. Kumar, A. Kumar, S. Chary, S. Senthil, P. K. Vaddavalli, and C. S. Garudadri, “Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects,” Cornea30(2), 121–126 (2011).
[CrossRef] [PubMed]

Shankar, H.

H. Shankar, D. Taranath, C. T. Santhirathelagan, and K. Pesudovs, “Repeatability of corneal first-surface wavefront aberrations measured with Pentacam corneal topography,” J. Cataract Refract. Surg.34(5), 727–734 (2008).
[CrossRef] [PubMed]

Siedlecki, D.

Siganos, D.

D. Siganos, P. Ferrara, K. Chatzinikolas, N. Bessis, and G. Papastergiou, “Ferrara intrastromal corneal rings for the correction of keratoconus,” J. Cataract Refract. Surg.28(11), 1947–1951 (2002).
[CrossRef] [PubMed]

Silvestrini, T. A.

T. E. Burris, P. C. Baker, C. T. Ayer, B. E. Loomas, M. L. Mathis, and T. A. Silvestrini, “Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study,” J. Cataract Refract. Surg.19(Suppl), 182–187 (1993).
[PubMed]

Smolek, M. K.

N. Maeda, S. D. Klyce, M. K. Smolek, and H. W. Thompson, “Automated keratoconus screening with corneal topography analysis,” Invest. Ophthalmol. Vis. Sci.35(6), 2749–2757 (1994).
[PubMed]

Song, J. C.

M. M. Lai, M. Tang, E. M. Andrade, Y. Li, R. N. Khurana, J. C. Song, and D. Huang, “Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes,” J. Cataract Refract. Surg.32(11), 1860–1865 (2006).
[CrossRef] [PubMed]

Souri, H.

M. A. Javadi, B. F. Motlagh, M. R. Jafarinasab, Z. Rabbanikhah, A. Anissian, H. Souri, and S. Yazdani, “Outcomes of penetrating keratoplasty in keratoconus,” Cornea24(8), 941–946 (2005).
[CrossRef] [PubMed]

Spoerl, E.

G. Wollensak, E. Spoerl, and T. Seiler, “Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus,” Am. J. Ophthalmol.135(5), 620–627 (2003).
[CrossRef] [PubMed]

Srivannaboon, S.

D. Z. Reinstein, S. Srivannaboon, and S. P. Holland, “Epithelial and stromal changes induced by intacs examined by three-dimensional very high-frequency digital ultrasound,” J. Refract. Surg.17(3), 310–318 (2001).
[PubMed]

Sterling, J.

S. M. Kymes, J. J. Walline, K. Zadnik, J. Sterling, M. O. Gordon, and Collaborative Longitudinal Evaluation of Keratoconus Study Group, “Changes in the quality-of-life of people with keratoconus,” Am. J. Ophthalmol.145(4), 611–617.e1 (2008).
[CrossRef] [PubMed]

Stuart, J. C.

Szkulmowski, M.

Szlag, D.

Tang, M.

Y. Li, M. Tang, X. Zhang, C. H. Salaroli, J. L. Ramos, and D. Huang, “Pachymetric mapping with Fourier-domain optical coherence tomography,” J. Cataract Refract. Surg.36(5), 826–831 (2010).
[CrossRef] [PubMed]

Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
[CrossRef] [PubMed]

M. M. Lai, M. Tang, E. M. Andrade, Y. Li, R. N. Khurana, J. C. Song, and D. Huang, “Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes,” J. Cataract Refract. Surg.32(11), 1860–1865 (2006).
[CrossRef] [PubMed]

Taranath, D.

H. Shankar, D. Taranath, C. T. Santhirathelagan, and K. Pesudovs, “Repeatability of corneal first-surface wavefront aberrations measured with Pentacam corneal topography,” J. Cataract Refract. Surg.34(5), 727–734 (2008).
[CrossRef] [PubMed]

Teus, M. A.

D. P. Piñero, J. L. Alio, M. A. Teus, R. I. Barraquer, and A. Uceda-Montañés, “Modeling the intracorneal ring segment effect in keratoconus using refractive, keratometric, and corneal aberrometric data,” Invest. Ophthalmol. Vis. Sci.51(11), 5583–5591 (2010).
[CrossRef] [PubMed]

Thakrar, V.

Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
[CrossRef] [PubMed]

Thompson, H. W.

N. Maeda, S. D. Klyce, M. K. Smolek, and H. W. Thompson, “Automated keratoconus screening with corneal topography analysis,” Invest. Ophthalmol. Vis. Sci.35(6), 2749–2757 (1994).
[PubMed]

Thompson, K.

Y. Yang, K. Thompson, and S. A. Burns, “Pupil location under mesopic, photopic, and pharmacologically dilated conditions,” Invest. Ophthalmol. Vis. Sci.43(7), 2508–2512 (2002).
[PubMed]

Tokunaga, T.

K. Kawana, K. Miyata, T. Tokunaga, T. Kiuchi, T. Hiraoka, and T. Oshika, “Central corneal thickness measurements using Orbscan II scanning slit topography, noncontact specular microscopy, and ultrasonic pachymetry in eyes with keratoconus,” Cornea24(8), 967–971 (2005).
[CrossRef] [PubMed]

Tomidokoro, A.

A. Tomidokoro, T. Oshika, S. Amano, S. Higaki, N. Maeda, and K. Miyata, “Changes in anterior and posterior corneal curvatures in keratoconus,” Ophthalmology107(7), 1328–1332 (2000).
[CrossRef] [PubMed]

Touboul, D.

C. Dauwe, D. Touboul, C. J. Roberts, A. M. Mahmoud, J. Kérautret, P. Fournier, F. Malecaze, and J. Colin, “Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus,” J. Cataract Refract. Surg.35(10), 1761–1767 (2009).
[CrossRef] [PubMed]

Uceda-Montañés, A.

D. P. Piñero, J. L. Alio, M. A. Teus, R. I. Barraquer, and A. Uceda-Montañés, “Modeling the intracorneal ring segment effect in keratoconus using refractive, keratometric, and corneal aberrometric data,” Invest. Ophthalmol. Vis. Sci.51(11), 5583–5591 (2010).
[CrossRef] [PubMed]

Vaddavalli, P. K.

H. L. Rao, A. U. Kumar, A. Kumar, S. Chary, S. Senthil, P. K. Vaddavalli, and C. S. Garudadri, “Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects,” Cornea30(2), 121–126 (2011).
[CrossRef] [PubMed]

Walline, J. J.

S. M. Kymes, J. J. Walline, K. Zadnik, J. Sterling, M. O. Gordon, and Collaborative Longitudinal Evaluation of Keratoconus Study Group, “Changes in the quality-of-life of people with keratoconus,” Am. J. Ophthalmol.145(4), 611–617.e1 (2008).
[CrossRef] [PubMed]

Warnicki, J. W.

Wojtkowski, M.

Wollensak, G.

G. Wollensak, E. Spoerl, and T. Seiler, “Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus,” Am. J. Ophthalmol.135(5), 620–627 (2003).
[CrossRef] [PubMed]

Yang, Y.

Y. Yang, K. Thompson, and S. A. Burns, “Pupil location under mesopic, photopic, and pharmacologically dilated conditions,” Invest. Ophthalmol. Vis. Sci.43(7), 2508–2512 (2002).
[PubMed]

Yazdani, S.

M. A. Javadi, B. F. Motlagh, M. R. Jafarinasab, Z. Rabbanikhah, A. Anissian, H. Souri, and S. Yazdani, “Outcomes of penetrating keratoplasty in keratoconus,” Cornea24(8), 941–946 (2005).
[CrossRef] [PubMed]

Yoshida, A.

A. Ishibazawa, S. Igarashi, K. Hanada, T. Nagaoka, S. Ishiko, H. Ito, and A. Yoshida, “Central corneal thickness measurements with Fourier-domain optical coherence tomography versus ultrasonic pachymetry and rotating Scheimpflug camera,” Cornea30(6), 615–619 (2011).
[CrossRef] [PubMed]

Zadnik, K.

S. M. Kymes, J. J. Walline, K. Zadnik, J. Sterling, M. O. Gordon, and Collaborative Longitudinal Evaluation of Keratoconus Study Group, “Changes in the quality-of-life of people with keratoconus,” Am. J. Ophthalmol.145(4), 611–617.e1 (2008).
[CrossRef] [PubMed]

Zhang, X.

Y. Li, M. Tang, X. Zhang, C. H. Salaroli, J. L. Ramos, and D. Huang, “Pachymetric mapping with Fourier-domain optical coherence tomography,” J. Cataract Refract. Surg.36(5), 826–831 (2010).
[CrossRef] [PubMed]

Zhao, M.

Am. J. Ophthalmol. (4)

S. M. Kymes, J. J. Walline, K. Zadnik, J. Sterling, M. O. Gordon, and Collaborative Longitudinal Evaluation of Keratoconus Study Group, “Changes in the quality-of-life of people with keratoconus,” Am. J. Ophthalmol.145(4), 611–617.e1 (2008).
[CrossRef] [PubMed]

G. Wollensak, E. Spoerl, and T. Seiler, “Riboflavin/ultraviolet-a-induced collagen crosslinking for the treatment of keratoconus,” Am. J. Ophthalmol.135(5), 620–627 (2003).
[CrossRef] [PubMed]

L. J. Maguire and W. M. Bourne, “Corneal topography of early keratoconus,” Am. J. Ophthalmol.108(2), 107–112 (1989).
[PubMed]

U. de Sanctis, A. Missolungi, B. Mutani, L. Richiardi, and F. M. Grignolo, “Reproducibility and repeatability of central corneal thickness measurement in keratoconus using the rotating Scheimpflug camera and ultrasound pachymetry,” Am. J. Ophthalmol.144(5), 712–718.e1 (2007).
[CrossRef] [PubMed]

Appl. Opt. (3)

Arch. Ophthalmol. (1)

N. Mamalis, C. W. Anderson, K. R. Kreisler, M. K. Lundergan, and R. J. Olson, “Changing trends in the indications for penetrating keratoplasty,” Arch. Ophthalmol.110(10), 1409–1411 (1992).
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Arch. Soc. Am. Ophthalmol. Optom. (1)

E. D. Blavatskaya, “Intralamellar homoplasty for the purpose of relaxation of refraction of the eye,” Arch. Soc. Am. Ophthalmol. Optom.6, 311–325 (1968).

Biomed. Opt. Express (2)

Cornea (4)

H. L. Rao, A. U. Kumar, A. Kumar, S. Chary, S. Senthil, P. K. Vaddavalli, and C. S. Garudadri, “Evaluation of central corneal thickness measurement with RTVue spectral domain optical coherence tomography in normal subjects,” Cornea30(2), 121–126 (2011).
[CrossRef] [PubMed]

A. Ishibazawa, S. Igarashi, K. Hanada, T. Nagaoka, S. Ishiko, H. Ito, and A. Yoshida, “Central corneal thickness measurements with Fourier-domain optical coherence tomography versus ultrasonic pachymetry and rotating Scheimpflug camera,” Cornea30(6), 615–619 (2011).
[CrossRef] [PubMed]

K. Kawana, K. Miyata, T. Tokunaga, T. Kiuchi, T. Hiraoka, and T. Oshika, “Central corneal thickness measurements using Orbscan II scanning slit topography, noncontact specular microscopy, and ultrasonic pachymetry in eyes with keratoconus,” Cornea24(8), 967–971 (2005).
[CrossRef] [PubMed]

M. A. Javadi, B. F. Motlagh, M. R. Jafarinasab, Z. Rabbanikhah, A. Anissian, H. Souri, and S. Yazdani, “Outcomes of penetrating keratoplasty in keratoconus,” Cornea24(8), 941–946 (2005).
[CrossRef] [PubMed]

Curr. Opin. Ophthalmol. (1)

T. E. Burris, “Intrastromal corneal ring technology: results and indications,” Curr. Opin. Ophthalmol.9(4), 9–14 (1998).
[CrossRef] [PubMed]

Int. Ophthalmol. Clin. (2)

L. T. Nordan, “Keratoconus: diagnosis and treatment,” Int. Ophthalmol. Clin.37(1), 51–63 (1997).
[CrossRef] [PubMed]

J. I. Barraquer, “Modification of refraction by means of intracorneal inclusions,” Int. Ophthalmol. Clin.6(1), 53–78 (1966).
[PubMed]

Invest. Ophthalmol. Vis. Sci. (4)

N. Maeda, S. D. Klyce, M. K. Smolek, and H. W. Thompson, “Automated keratoconus screening with corneal topography analysis,” Invest. Ophthalmol. Vis. Sci.35(6), 2749–2757 (1994).
[PubMed]

A. Pérez-Escudero, C. Dorronsoro, L. Sawides, L. Remón, J. Merayo-Lloves, and S. Marcos, “Minor influence of myopic laser in situ keratomileusis on the posterior corneal surface,” Invest. Ophthalmol. Vis. Sci.50(9), 4146–4154 (2009).
[CrossRef] [PubMed]

D. P. Piñero, J. L. Alio, M. A. Teus, R. I. Barraquer, and A. Uceda-Montañés, “Modeling the intracorneal ring segment effect in keratoconus using refractive, keratometric, and corneal aberrometric data,” Invest. Ophthalmol. Vis. Sci.51(11), 5583–5591 (2010).
[CrossRef] [PubMed]

Y. Yang, K. Thompson, and S. A. Burns, “Pupil location under mesopic, photopic, and pharmacologically dilated conditions,” Invest. Ophthalmol. Vis. Sci.43(7), 2508–2512 (2002).
[PubMed]

J. Cataract Refract. Surg. (9)

M. M. Lai, M. Tang, E. M. Andrade, Y. Li, R. N. Khurana, J. C. Song, and D. Huang, “Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes,” J. Cataract Refract. Surg.32(11), 1860–1865 (2006).
[CrossRef] [PubMed]

T. E. Burris, P. C. Baker, C. T. Ayer, B. E. Loomas, M. L. Mathis, and T. A. Silvestrini, “Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: an eye-bank eye study,” J. Cataract Refract. Surg.19(Suppl), 182–187 (1993).
[PubMed]

J. Colin, B. Cochener, G. Savary, and F. Malet, “Correcting keratoconus with intracorneal rings,” J. Cataract Refract. Surg.26(8), 1117–1122 (2000).
[CrossRef] [PubMed]

D. Siganos, P. Ferrara, K. Chatzinikolas, N. Bessis, and G. Papastergiou, “Ferrara intrastromal corneal rings for the correction of keratoconus,” J. Cataract Refract. Surg.28(11), 1947–1951 (2002).
[CrossRef] [PubMed]

J. L. Alió, T. F. Salem, A. Artola, and A. A. Osman, “Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis,” J. Cataract Refract. Surg.28(9), 1568–1574 (2002).
[CrossRef] [PubMed]

Y. Li, M. Tang, X. Zhang, C. H. Salaroli, J. L. Ramos, and D. Huang, “Pachymetric mapping with Fourier-domain optical coherence tomography,” J. Cataract Refract. Surg.36(5), 826–831 (2010).
[CrossRef] [PubMed]

C. Dauwe, D. Touboul, C. J. Roberts, A. M. Mahmoud, J. Kérautret, P. Fournier, F. Malecaze, and J. Colin, “Biomechanical and morphological corneal response to placement of intrastromal corneal ring segments for keratoconus,” J. Cataract Refract. Surg.35(10), 1761–1767 (2009).
[CrossRef] [PubMed]

H. Shankar, D. Taranath, C. T. Santhirathelagan, and K. Pesudovs, “Repeatability of corneal first-surface wavefront aberrations measured with Pentacam corneal topography,” J. Cataract Refract. Surg.34(5), 727–734 (2008).
[CrossRef] [PubMed]

S. A. Read, M. J. Collins, D. R. Iskander, and B. A. Davis, “Corneal topography with Scheimpflug imaging and videokeratography: comparative study of normal eyes,” J. Cataract Refract. Surg.35(6), 1072–1081 (2009).
[CrossRef] [PubMed]

J. Opt. Soc. Am. A (1)

J. Refract. Surg. (3)

G. Kamburoglu, A. Ertan, and O. Saraçbasi, “Measurement of depth of Intacs implanted via femtosecond laser using Pentacam,” J. Refract. Surg.25(4), 377–382 (2009).
[CrossRef] [PubMed]

D. Z. Reinstein, S. Srivannaboon, and S. P. Holland, “Epithelial and stromal changes induced by intacs examined by three-dimensional very high-frequency digital ultrasound,” J. Refract. Surg.17(3), 310–318 (2001).
[PubMed]

S. Barbero, S. Marcos, J. Merayo-Lloves, and E. Moreno-Barriuso, “Validation of the estimation of corneal aberrations from videokeratography in keratoconus,” J. Refract. Surg.18(3), 263–270 (2002).
[PubMed]

Ophthalmology (2)

A. Tomidokoro, T. Oshika, S. Amano, S. Higaki, N. Maeda, and K. Miyata, “Changes in anterior and posterior corneal curvatures in keratoconus,” Ophthalmology107(7), 1328–1332 (2000).
[CrossRef] [PubMed]

Y. Li, D. M. Meisler, M. Tang, A. T. H. Lu, V. Thakrar, B. J. Reiser, and D. Huang, “Keratoconus diagnosis with optical coherence tomography pachymetry mapping,” Ophthalmology115(12), 2159–2166 (2008).
[CrossRef] [PubMed]

Opt. Express (3)

Refract. Corneal Surg. (1)

Y. S. Rabinowitz and P. J. McDonnell, “Computer-assisted corneal topography in keratoconus,” Refract. Corneal Surg.5(6), 400–408 (1989).
[PubMed]

Surv. Ophthalmol. (1)

Y. S. Rabinowitz, “Keratoconus,” Surv. Ophthalmol.42(4), 297–319 (1998).
[CrossRef] [PubMed]

Supplementary Material (3)

» Media 1: AVI (5973 KB)     
» Media 2: AVI (1922 KB)     
» Media 3: AVI (4198 KB)     

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Figures (9)

Fig. 1
Fig. 1

(a) Example of B-Scan from a keratoconic patient. (b) Same B-scan after the application of the denoising algorithm.

Fig. 2
Fig. 2

(a) Semi-logarithmic representation of the 3-D image histogram using normalized intensity (blue points) and fitted data provided by the statistics of the Otsu’s statistical thresholding method (red points). (b) Result of the multi-modal fitting in red (9 different number of classes were found). In (a) and (b) classes are represented by dash black lines (c) Result of the application of the Otsu’s algorithm on a cross sectional image. (d) Result of the application of the multimodal algorithm on the same cross sectional image.

Fig. 3
Fig. 3

(a) (Media 1) Data processed applying the Otsu’s method, and therefore only considering the signal composed by only two classes (noise and signal). (b) (Media 2) Volumetric clustering of the data after denoising (cornea is represented in red and the iris is represented in green).

Fig. 4
Fig. 4

(Media 3). Illustration of the multilayer segmentation in a keratoconic cornea implanted with an ICRS, showing the posterior corneal surface (white), ICRS (yellow) and the anterior corneal surface (orange, movie only).

Fig. 5
Fig. 5

(a) Segmented (green). (b) Pupil edge fitting (detected edge in yellow and ellipse fitting in green). (c) ICRS inner diameter edge fit in the post-operative cornea (red line, and center as a red asterisk) and pupil center (green cross) (d) Evaluation of the same optical zone (in red) in the pre-operative cornea, using the pupil center as a reference.

Fig. 6
Fig. 6

Effect of the ICRS distortion on the corneal posterior surface. Left: Non-corrected image (red). Right: image after optical distortion correction of the ICRS (green).

Fig. 7
Fig. 7

(a) Quantitative anterior and posterior corneal elevation maps of a keratoconic cornea. (b) Quantitative post-ICRS anterior and posterior corneal elevation map. All data are after refraction distortion correction, and for a 6-mm zone.

Fig. 8
Fig. 8

Quantitative pachymetry map of keratoconic cornea (a) before and (b) after ICRS implantation. Data are for a 6-mm zone.

Fig. 9
Fig. 9

3-D analysis of the orientation (with respect to the pupil plane) and average depth (with respect to the anterior cornea) of the left and right ICRS. The red arrows are normal to the plane of the ICRS, and the yellow arrows are normal to the pupil.

Tables (2)

Tables Icon

Table 1 Radii of the cornea before and after ICRS surgery

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Table 2 Asphericities of the cornea before and after ICRS surgery

Metrics