Cornea - ARVO

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ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group - Corneastudies will be required to elucidate the effectiveness of this noninvasivetechnique.Commercial Relationships: Raksha Urs, None; Harriet Lloyd,None; Ronald H. Silverman, NoneSupport: AIUM EER; NIH Grant EY021529; Research to PreventBlindnessProgram Number: 1617 Poster Board Number: D0252Presentation Time: 8:30 AM - 10:15 AMLong Term Follow-Up of Corneal Topographic Indices FollowingCollagen Crosslinking In Eyes with KeratoconusErick Hernández-Bogantes, Lihteh Wu, David Flikier. Instituto deCirugía Ocular, San José, Costa Rica.Purpose: To compare the pre-treatment and 5 year post-treatmentvisual acuity and corneal topographic indices in eyes withkeratoconus that were treated with corneal collagen crosslinking.Methods: An observational, uncontrolled, retrospective study of 7patients (12 eyes) with keratoconus that were treated with epitheliumoffcorneal collagen crosslinking between March and December of2007 was conducted. Pre-treatment and 5 year post-treatment anteriorcorneal surface (keratoconus index, index of vertical asymmetry,index of surface variance, central keratoconus index, minimum radiusof curvature, index of height asymmetry, index of heightdecentration) and normalized Belin-Ambrosio indices (frontelevation, back elevation, pachymetric progression, corneal thinnestpoint and the total analysis) were obtained by the Pentacamtopographer, Oculus Inc. (Wetzlar, Germany). The uncorrected visualacuity and best corrected visual acuity were also compared.Results: The 5 year follow-up showed that both central keratoconusindex (P= 0.0452) and best corrected visual acuity (P= 0.0313)improved following corneal collagen crosslinking. At 5 years offollow-up, there were no statistically significant differences betweenthe pre-operative and post-operative values of either the otheranterior surface variables or the normalized Berlin-Ambrosio indices.Conclusions: Even though the surface of the cornea does not appearto be dramatically altered after five years of corneal collagencrosslinking, improvement in visual acuity is obtained and remainsconstant.Commercial Relationships: Erick Hernández-Bogantes, None;Lihteh Wu, Heidelberg Engineering (R); David Flikier, NoneProgram Number: 1618 Poster Board Number: D0253Presentation Time: 8:30 AM - 10:15 AMComparison of corneal changes between standard andtransepithelial riboflavin-UVA crosslinking method usingmultiphoton microscopy and second harmonic imagingPraveena Gupta 1 , Best Anyama 2 , Kevin M. Wells 2 , MassoudMotamedi 3, 1 , Bernard F. Godley 1 , Gracie Vargas 3 . 1 Ophthalmology& Visual Sciences, Univ of Texas Medical Branch, Galveston, TX;2 School of Medicine, University of Texas medical Branch,Galveston, TX; 3 Center for Biomedical Engineering, Univ of TexasMedical Branch, Galveston, TX.Purpose: Corneal crosslinking procedures are offered as a treatmentfor keratoconus and corneal ectasic disorders. This study wasundertaken to investigate the comparative stromal changes after theUVA-crosslinking on a riboflavin-debrided and a riboflavintransepithelialtreated porcine cornea using multiphoton microscopyand second harmonic generation signals.Methods: Fifteen fresh pig eyes were treated using either thestandard method of riboflavin-UVA crosslinking or thetransepithelial method (riboflavin TRIS-EDTA) for 30 min atirradiance of 3mW/cm2. All corneas were then stained with a celldeath marker and processed for non-invasive multiphotonmicroscopy and second harmonic signal imaging. Data collectedwere analyzed using image J.Results: Standard CXL treatment resulted in severe loss of theclassic interwoven collagen architecture all the way up to 300 uMdepths, whereas, similar changes were noted only up to 150 uM depthin the TE method of CXL. Significantly higher numbers of deadkeratocytes were counted at all the depths in the standard CXLexposed eyes in contrast to fewer keratocyte deaths that were morepronounced only in the anterior stroma in the TE-CXL treatedcorneas (p
ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group - Corneawill be expanded to include an anisotropic, fiber-dependenthyperelastic material formulation.Figure 1: Corneal flap attached to biaxial extensometer.Commercial Relationships: William A. Eddington, Avedro Inc.(E); Marc D. Friedman, Avedro Inc (E); Evan A. Sherr, Avedro,Inc. (E); David Muller, Avedro Inc (E)Program Number: 1620 Poster Board Number: D0255Presentation Time: 8:30 AM - 10:15 AMFinite Element Analysis of Treatment of Corneal Astigmatismwith Collagen CrosslinkingIBRAHIM SEVEN 1, 2 , Abhijit Sinha Roy 1 , William J. Dupps 1, 2 .1 Ophthalmology, Cleveland Clinic Cole Eye Inst, Cleveland, OH;2 Biomedical Engineering, Cleveland Clinic Lerner Research Institute,Cleveland, OH.Purpose: To test the hypothesis that selective collagen crosslinkingcan alter corneal astigmatism and to assess the effects of treatmentorientation and pattern.Methods: 3D geometry of a patient with corneal astigmatism wasmeasured by a Scheimpflug tomography system (Pentacam v.1.61).Elevation data was fit and extrapolated with 12th order Zernikepolynomials routine which was coded in Python2.7. The extrapolateddata was imported into Solidworks (ver. 2011). The geometry wasmeshed with hexahedral elements by Trugrid (v. 2.3.3). Cornealbiomechanical properties were defined as nonlinear, isotropic andincompressible. The intra-ocular pressure was assumed as 15 mmHg.Finite element analyses were performed using Abaqus (v. 6.11).Since the in vivo (or pre-operation) geometry was pre-stressed byintra-ocular pressure, the geometry was solved for the no-loadcondition and pre-stresses were calculated. We simulated 4 differentcrosslinking treatment patterns with a stiffening factor of 2 andeffective depth of 300 um. The treatment was simulated with a bowtiepattern oriented on the steep astigmatism axis (pattern1), a bow-tiepattern oriented on the flat astigmatism axis (pattern2), a fan pattern(pattern3), and a central ellipse pattern oriented on the flatastigmatism axis (pattern4). The corneal anterior surface coordinateswere extracted at the end of the each simulation and the anteriorsurface axial curvature was calculated. The refractive index was asassumed as 1.3375.Results: Keratometry (Sim K) values in the preoperative eye (invivo) were 44.85/46.22@78. The SimK value changed to44.06/46.62@90, 44.83/45.88@45, 44.76/46.27@84,44.64/45.64@51 with pattern1, pattern2, pattern3, and pattern4treatment, respectively. The astigmatism value was 1.37in the preoperationstage. The value changed to 2.56, 1.05, 1.51, and 1.00 withpattern1, pattern2, pattern3, and pattern4 treatment, respectively.Conclusions: In this pilot study, simulated patterned collagencrosslinking had an effect on corneal astigmatism. Treatments on thesteep axis increased astigmatism, while treatments orthogonal to thesteep axis decreased astigmatism. Additional clinical geometries withregular and irregular astigmatism will be investigated and modelingFigure 1 - Comparison of different treatment patternsCommercial Relationships: IBRAHIM SEVEN, None; AbhijitSinha Roy, Carl Zeiss Meditec (F), Cleveland Clinic Innovations (P),Topcon Inc. (F); William J. Dupps, Zeimer (C), Topcon (F), Avedro(F), Carl Zeiss Meditec (F), Cleveland Clinic Innovations (P)Program Number: 1621 Poster Board Number: D0256Presentation Time: 8:30 AM - 10:15 AMCorneal geometric stress factor to evaluate response to cornealcollagen cross-linking in keratoconusRiccardo Vinciguerra 1, 2 , Cynthia J. Roberts 3 , Ashraf M. Mahmoud 3 ,Claudio Azzolini 2 , Paolo Vinciguerra 1 . 1 Opthalmology, HumanitasClinical and Research Center, Milan, Italy; 2 Dept. of Surgical andMorphological Sciences, University of Insubria, Circolo Hospital,Varese, Italy; 3 Ophthalmology and Biomedical Engineering, TheOhio State University, Columbus, OH.Purpose: To evaluate corneal stress distribution based purely ongeometry without consideration of loading via intraocular pressure,pre and post corneal collagen cross-linking (CXL) with a newtomographic parameter, “Corneal Geometric Stress Factor”.Methods: Tomographic data from four hundred and eighty subjects(323 right eyes and 340 left eyes) were collected retrospectively fromIstituto Clinico Humanitas (Rozzano, Italy) with up to 70 months pre-CXL and 60 months post-CXL. Pentacam U12 files (OculusOptikgerate GmbH, Wetzlar, Germany) were transferred to The OhioState University and processed independently using custom software.Corneal Geometric Stress Factor (CGSF) was calculated atcorresponding points from curvature and pachymetric maps to createa CGSF map. CGSF evaluates the cornea’s contribution to Hoopstress without considering the applied load (intraocular pressure) andit can be expressed as the radius of curvature over twice of thethickness (CGSF=R/2t). Cone Location and Magnitude Index(CLMI) and Flat zone Location and Magnitude Index (FLMI) wereapplied to the CGSF map to obtain maximum stress and minimumstress and to calculate the level of asymmetry in the stress pattern.Pre and post CXL regression analyses were performed.Results: Regression analysis showed a significant (p
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