Cornea - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group - Corneavalues parallelto failure of corneal hydration. It was found that duration andmetabolic control ofdiabetes did not change the biomechanical properties of cornea.Commercial Relationships: Faruk Ozturk, None; Serkan Akkaya,None; Ertugrul Can, NoneProgram Number: 1641 Poster Board Number: D0276Presentation Time: 8:30 AM - 10:15 AMCollagen Macrostructure and Corneal Shape: Lessons fromDifferent SpeciesMoritz Winkler 1 , Yilu Xie 2 , Tiffany Yuen 1 , Golroxan Shoa 1 , RobertHueter 3 , Kathy K. Svoboda 4 , Christopher J. Murphy 5 , Donald J.Brown 2 , James V. Jester 2, 1 . 1 Biomedical Engineering, University ofCalifornia, Irvine, Irvine, CA; 2 Gavin Herbert Eye Institute,University of California, Irvine, Irvine, CA; 3 Mote MarineLaboratory, Sarasota, FL; 4 Biomedical Sciences, Texas A&M HealthScience Center, Dallas, TX; 5 Department of Surgical andRadiological Sciences, University of California, Davis, Davis, CA.Purpose: The cornea plays a critical role both as a protective windowto the eye and as a refractive lens. In aquatic vertebrates, it provideslittle refractive power, while in terrestrial vertebrates corneal shapeneeds to be precisely controlled to project a focused image on theretina. Little is known about the changes in the structuralorganization of corneal collagen during evolution. The purpose ofthis study was to begin to characterize the macrostructuralorganization of corneal collagen in divergent species in order touncover basic mechanisms controlling corneal shape.Methods: Eyes from various species (fish, shark, birds, mammals)were fixed under pressure using paraformaldehyde to control postmortemswelling. Serial full-width (limbus to limbus) cross-sections(250μm thick) were cut using a vibratome. Sections were imagedusing nonlinear optical high resolution macroscopy (NLO-HRMac)of second harmonic generated (SHG) signals. 3-D images wererendered using Amira software, and collagen fiber structures werequantified with custom-written ImageJ macros.Results: In aquatic vertebrates stromal collagen macrostructureconsisted of simplified layers (stacks) of fibers that extended fromlimbus to limbus as continuous sheets of collagen, much like‘plywood’ in construction. Adjacent sheets were rotated 87°, formingorthogonal plies, with successive layers showing a continual rotationof over 360°. In birds collagen sheets were organized into distinctfibers with a uniform branching and fusing pattern similar to that ofchicken wire and presented a honeycomb appearance. Fibers in thesame plane appeared to extend from limbus to limbus, and successivelayers showed a 270° rotation through 2/3 stromal depth, very similaryet distinct from fish and shark. By contrast, collagen fiberorganization in mammals was irregular with varying degrees ofbranching depending on the species (human > dog > cat > rabbit).Mammals also lacked orthogonal rotational, nor were fibersconstrained to extend from limbus to limbus within the same plane.Conclusions: We have previously shown in the human cornea thatcollagen fiber branching and interconnectivity is associated withtissue rigidity. In this study, fiber branching was detected in corneasfrom terrestrial vertebrates suggesting that branching and increasedcorneal rigidity may play a role in the evolutionary adaptation of thecornea from a protective window to a refractive lens.Commercial Relationships: Moritz Winkler, None; Yilu Xie,None; Tiffany Yuen, None; Golroxan Shoa, None; Robert Hueter,None; Kathy K. Svoboda, None; Christopher J. Murphy, OcularServices On Demand (I), Ocular Services On Demand (C), PlatypusTechnologies LLC (I), Imbed LLC (I), EyeKor LLC (I), Allergan(C), Genentech (C), Sarcode (C), Covance (C); Donald J. Brown,None; James V. Jester, NoneSupport: NIH Grant EY018665, Research to Prevent Blindness, Inc.,Discovery Eye Foundation, and the Skirball Program in MolecularOphthalmologyProgram Number: 1642 Poster Board Number: D0277Presentation Time: 8:30 AM - 10:15 AMInter- and Intra-Lamellar Slippage of Collagen Fibrils as aPotential Mechanism of Keratoconus ProgressionMichael Koster 1 , Craig Boote 2 , Keith M. Meek 2 , Priscilla G. Fowler 3 ,Christopher A. Girkin 3 , Guenther Meschke 1 , Rafael Grytz 3 . 1 Instituefor Structural Mechanics, Ruhr University Bochum, Bochum,Germany; 2 School of Optometry and Vision Sciences, CardiffUniversity, Cardiff, United Kingdom; 3 Ophthalmology, University ofAlabama at Birmingham, Birmingham, AL.Purpose: To assess if inter- and intra-lamellar slippage of collagenfibrils may lead to progressive cone formation in keratoconus.Methods: A generic finite element model of the human eye wasgenerated that incorporates the micro-architecture of collagen fibrilsin the corneo-scleral shell. Inter- and intra-lamellar slippage wassimulated through residual strains of collagen fibrils using amicrostructure-based constitutive formulation. Progressive inter- andintra-lamellar slippage was imposed to an eccentric, 4-mm-diameterarea of the cornea while the model was subjected to normal IOP (15mmHg). Topographic results were compared to clinical observationof a keratoconus patient with an eccentric cone.Results: Increasing inter- and intra-lamellar slippage led toprogressive cone formation of the cornea. The results were in goodagreement with topographic observation of keratoconus patients witheccentric cone.Conclusions: The numerical results support the assumption thatinter- and intra-lamellar slippage of collagen fibrils may be theunderlying mechanism that leads to progressive cone formation inkeratoconus.Numerical simulation of keratoconus progression showing thedevelopment of an eccentric cone due to inter- and intra-lamellarslippage of corneal collagen fibrils.Commercial Relationships: Michael Koster, None; Craig Boote,None; Keith M. Meek, None; Priscilla G. Fowler, None;Christopher A. Girkin, SOLX (F), Heidelberg Engineering (F);Guenther Meschke, None; Rafael Grytz, NoneSupport: EyeSight Foundation of Alabama; Research to PreventBlindness Physician-Scientist AwardProgram Number: 1643 Poster Board Number: D0278Presentation Time: 8:30 AM - 10:15 AMClear Corneal Incision: Sealability of the Manual Versus LensARlaser generated Full Thickness Incision©2013, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permissionto reproduce any abstract, contact the ARVO Office at arvo@arvo.org.