Distinguishing Keratoconic Eyes and Healthy Eyes Using Ultrahigh-Resolution Optical Coherence Tomography-Based Corneal Epithelium Thickness Mapping.

PURPOSE To find differences in epithelial thickness (ET) maps of eyes with keratoconus (KC) and healthy eyes. DESIGN Institutional cross-sectional study. METHODS In this study 40 keratoconic eyes and 76 healthy eyes were scanned using a custom-built ultrahigh-resolution optical coherence tomography system. Automated segmentation ET maps with 17 subsectors were calculated (central, temporal inferior, temporal superior, nasal inferior, and nasal superior area). The thinnest point of the epithelium (minET), the thickest point of the epithelium (maxET), and the thinnest point diagonally opposing the thickest point (ETmax/op) were additional parameters. Ratios were calculated as follows: minET/diagonally opposing point (R1), maxET/diagonally opposing point (R2), inferior temporal area/superior nasal area (RTI/NS), and inferior/superior hemisphere (RI/S). Furthermore, collected parameters were analyzed regarding their diagnostic accuracy (area under the curve; AUC). RESULTS Statistically significant differences were as follows: central ET, 46.25 ± 2.56/50.91 ± 1.66; minET, 38.50 ± 2.10/46.79 ± 1.27; ETmax/op, 47.14 ± 2.45/49.60 ± 1.57; temporal inferior area: 43.93 ± 2.95/51.04 ± 1.51 (all mean ± standard deviation, μm); R1, 0.76 ± 0.09/0.93 ± 0.04; R2, 1.08 ± 0.04/1.21 ± 0.16; RTI/NS, 0.85 ± 0.08/1.02 ± 0.04; RI/S: 0.92 ± 0.07/0.99 ± 0.02. AUC values were R1: 0.979 (confidence interval [CI]: 0.957-1.000), RTI/NS: 0.977 (CI: 0.951-1.000), and minET: 0.928 (CI: 0.880-0.977). CONCLUSIONS Epithelial thickness maps could clearly visualize different ET patterns. Parameters with the highest potential of diagnostic discrimination between eyes with KC and healthy eyes were, in descending order, R1, RTI/NS, and minET. Consequently, epithelial thickness irregularity and asymmetry seem to be the most promising diagnostic factor in terms of discriminating between keratoconic eyes and healthy eyes.

[1]  Sander R. Dubovy,et al.  Topographic thickness of Bowman's layer determined by ultra-high resolution spectral domain-optical coherence tomography. , 2011, Investigative ophthalmology & visual science.

[2]  Yan Li,et al.  Corneal epithelial thickness mapping by Fourier-domain optical coherence tomography in normal and keratoconic eyes. , 2012, Ophthalmology.

[3]  Vincent Borderie,et al.  Fourier-domain optical coherence tomography imaging in keratoconus: a corneal structural classification. , 2013 .

[4]  A. Kanellopoulos,et al.  OCT corneal epithelial topographic asymmetry as a sensitive diagnostic tool for early and advancing keratoconus , 2014, Clinical ophthalmology.

[5]  Angelika Unterhuber,et al.  Effect of hyaluronic acid on tear film thickness as assessed with ultra‐high resolution optical coherence tomography , 2015, Acta ophthalmologica.

[6]  M. López,et al.  Assessment of Corneal Epithelial Thickness in Asymmetric Keratoconic Eyes and Normal Eyes Using Fourier Domain Optical Coherence Tomography , 2016, Journal of ophthalmology.

[7]  R. D. Stulting,et al.  Risk factors and prognosis for corneal ectasia after LASIK. , 2002, Ophthalmology.

[8]  Leopold Schmetterer,et al.  Effect of a Matrix Therapy Agent on Corneal Epithelial Healing After Standard Collagen Cross-linking in Patients With Keratoconus: A Randomized Clinical Trial. , 2016, JAMA ophthalmology.

[9]  Yan Li,et al.  Subclinical keratoconus detection by pattern analysis of corneal and epithelial thickness maps with optical coherence tomography , 2016, Journal of cataract and refractive surgery.

[10]  S. Klyce,et al.  Automated topographic screening for keratoconus in refractive surgery candidates. , 1996, The CLAO journal : official publication of the Contact Lens Association of Ophthalmologists, Inc.

[11]  Marine Gobbe,et al.  Corneal epithelial thickness profile in the diagnosis of keratoconus. , 2009, Journal of refractive surgery.

[12]  A. Roychoudhury,et al.  Epithelial remodeling as basis for machine-based identification of keratoconus. , 2014, Investigative ophthalmology & visual science.

[13]  Ronald H. Silverman,et al.  Epithelial Thickness in the Normal Cornea: Three-dimensional Display With Very High Frequency Ultrasound , 2008 .

[14]  Ronald H Silverman,et al.  Epithelial, stromal, and total corneal thickness in keratoconus: three-dimensional display with artemis very-high frequency digital ultrasound. , 2010, Journal of refractive surgery.

[15]  S. Priglinger,et al.  Corneal Epithelial Remodeling Induced by Small Incision Lenticule Extraction (SMILE). , 2016, Investigative ophthalmology & visual science.

[16]  Y. Rabinowitz.  Videokeratographic indices to aid in screening for keratoconus. , 1995, Journal of refractive surgery.

[17]  Hong Jiang,et al.  Vertical and Horizontal Corneal Epithelial Thickness Profile Using Ultra-High Resolution and Long Scan Depth Optical Coherence Tomography , 2014, PloS one.

[18]  O. Sandali,et al.  Corneal epithelial thickness mapping using Fourier‐domain optical coherence tomography for detection of form fruste keratoconus , 2015, Journal of cataract and refractive surgery.

[19]  R. Silverman,et al.  Comparison of very‐high‐frequency ultrasound and spectral‐domain optical coherence tomography corneal and epithelial thickness maps , 2016, Journal of cataract and refractive surgery.

[20]  Jianhua Wang,et al.  Topographical thickness of the epithelium and total cornea after hydrogel and PMMA contact lens wear with eye closure. , 2003 .

[21]  Jianhua Wang,et al.  Entire Thickness Profiles of the Epithelium and Contact Lens In Vivo Imaged With High-Speed and High-Resolution Optical Coherence Tomography , 2013, Eye & contact lens.

[22]  Angelika Unterhuber,et al.  Measurement of tear film thickness using ultrahigh-resolution optical coherence tomography. , 2013, Investigative ophthalmology & visual science.

[23]  M. Deist,et al.  Iatrogenic keratectasia after laser in situ keratomileusis for less than -4.0 to -7.0 diopters of myopia. , 2000, Journal of cataract and refractive surgery.

[24]  L. Schmetterer,et al.  Ultrahigh-resolution OCT imaging of the human cornea. , 2017, Biomedical optics express.

[25]  Jianhua Wang,et al.  Vertical and horizontal thickness profiles of the corneal epithelium and Bowman's layer after orthokeratology. , 2013, Investigative ophthalmology & visual science.