Cornea - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group - Corneanonlinear signal presented a maximum close to the Bowman’s layerand a uniform decrease with depth typical of a non-irradiated cornea.On the opposite, fs-CXL corneas exhibited a marked increase innonlinear signal at the treated volume with no effect on nearbycorneal layers, presumably indicative of localized changes incollagen distribution. This was revealed by means of the regular XYmultiphoton images at different depth positions throughout the entirestroma.Conclusions: This study demonstrates the feasibility of usinginfrared fs-laser pulses to perform well-localized 3-dimensional CXLtreatments within the cornea. The technique has been proven to beprecise with surrounded regions hardly affected and no thermaleffects. The combination of both surgical and monitoring functionsinto a unique fs-laser system has the potential to be a tool in clinicalenvironments and could be the basis to establish a new techniquecapable of monitoring CXL procedures in real-time.Commercial Relationships: Juan M. Bueno, None; Harilaos S.Ginis, Universidad de Murcia (P); Raquel Palacios, None;Alexandros Pennos, None; Pablo Artal, AMO (C), Voptica SL (P),Voptica SL (I), AMO (F), Calhoun Vision (F), Calhoun Vision (C),AcuFocus (C)Support: Ministerio de Educación y Ciencia, Spain (grants FIS2010-14926 and CSD2007-00013) and Fundación Séneca, Región deMurcia, Spain (grant 4524/GERM/06).Program Number: 5288 Poster Board Number: C0207Presentation Time: 2:45 PM - 4:30 PMAccelerated corneal cross-linking with pulsed lightPavel Kamaev, William A. Eddington, Sara Rood-Ojalvo, Marc D.Friedman, David Muller. Research, Avedro, Waltham, MA.Purpose: Corneal collagen cross-linking (CXL) with riboflavin (RF)strengthens corneas affected by keratoconus. This treatment involvesirradiation with continuous ultraviolet-A (UVA) which deoxygenatesthe cornea and makes keratocytes more susceptible to theaction of light. In order to avoid this self-limiting factor of CXL, wepropose to apply pulsed UVA to allow the tissue to re-oxygenate andto increase efficiency of CXL.Methods: Porcine eye globes were shipped overnight on ice from anabattoir (SiouxPreme, Sioux City, IA). The corneas were then deepithelializedand 0.1% riboflavin-5’-phosphate solution was appliedtopically during 20 min at 37°C. Eyes were placed in a beaker filledwith oxygen and irradiated for 3 min continuously or for 6 minuteswith pulsed UVA light (365 nm, 1.5 sec on / 1.5 sec off) at 30mW/cm2 using a shutter (Sutter Instrument, Novato, CA). Cornealflaps (200 µm thick) were excised from the eyes using an Intralasefemtosecond laser (Abbot Medical Optics, Santa Ana, CA). The flapswere placed into a biaxial extensometer (CellScale Biotester 5000,Waterloo, ON), using biorake attachments with 5 tines spanning awidth of 3mm. Each sample was stretched at a constant rate of 4µm/s in saline at 37°C until sample failure. The flaps were thenwashed with distilled water, dried in a vacuum and digested at 65°Cwith 2.5 units/ml of papain in 1x PBS (pH 7.4) containing 2 mM L-cysteine and 2 mM EDTA. Fluorescence of the papain digests wasrecorded at 450 nm in a QM-40 Spectrofluorometer (PhotonTechnology Int., London, Ontario, Canada) using excitation of 360nm.Results: Continuous irradiation of the corneal tissue in presence ofRF resulted in a quick depletion of dissolved oxygen. This happensvia the process of generation of reactive oxygen species (includingsinglet oxygen) and following cross-linking, mediated by freeradicals. With pulsed fractionation of UVA radiation, cross-linkingefficiency is improved by allowing the re-diffusion of oxygen duringpauses in exposure.Conclusions: Our work confirmed that re-oxygenation of corneaduring UVA pulsation increases efficiency of the CXL. From aclinical perspective, accelerated CXL with pulsed light would lead toa reduced dose for the same amount of corneal stiffening andtherefore a better safety profile.Commercial Relationships: Pavel Kamaev, Avedro (E); WilliamA. Eddington, Avedro Inc. (E); Sara Rood-Ojalvo, Avedro Inc. (E);Marc D. Friedman, Avedro Inc (E); David Muller, Avedro Inc (E)Program Number: 5289 Poster Board Number: C0208Presentation Time: 2:45 PM - 4:30 PMLong term follow-up of stiffening of rabbit corneas by WST11using near infrared lightArie L. Marcovich 1, 2 , Alexander Brandis 1 , Ilan Feine 3 , Iddo Pinkas 1 ,Ruth Goldschmidt 1 , Vyacheslav Kalchenko 4 , Daniel H. Wagner 5 ,Yoram Salomon 3 , Avigdor Scherz 1 . 1 Plant Sciences, WeizmannInstitute of Science, Rehovot, Israel; 2 Ophthalmology, KaplanMedical Center, Rehovot, Israel; 3 Biological Regulation, WeizmannInstitute of Science, Rehovot, Israel; 4 Veterinary Resources,Weizmann Institute of Science, Rehovot, Israel; 5 Materials andInterfaces, Weizmann Institue of Science, Los Angeles, CA.Purpose: To evaluate the efficacy and safety of photochemicalcorneal stiffening by Pd- bacteriochlorin 13’-(2-sulfoethyl)-amidedipotassium salt (WST11) and near infrared (NIR) illumination,using rabbit eye models.Methods: Corneas of living rabbits were pretreated topically with 2.5mg/ml WST11 in saline or in 20% dextran T-500 for 20 minutes, andilluminated with a NIR diode laser (755 nm, 10 mW/cm2) for 30minutes. Corneas of untreated fellow eyes served as controls. Therabbits were sacrificed after one month and 4 months. Corneal stripsof 4 mm width were excised. Ultimate stress and Young’s modulusmeasurements were performed using a biomechanical tester.Comparative studies were performed with standardriboflavin/ultraviolet-A light (UVA) treatment. Histology, electronspin resonance, fluorescence microscopy and optical coherencetomography (OCT) were used to evaluate treatment effects.Results: WST11/NIR treatment significantly increased cornealstiffness following treatment, compared to untreated contralateraleyes. After 1 month the ultimate stress and Young’s modulus oftreated corneas increased by 113%, and 80% respectively. WST11 in20% dextran T-500/NIR had similar stiffening results, but markedlyreduced post-treatment edema and time of epithelial healingcompared to WST11 without dextran. After 4 months, treated corneasmaintained biomechanical stiffness values measured at 1 month posttreatment. OCT demonstrated a demarcation line in the anterior thirdof the corneal stroma. Histology showed a reduction in the keratocytepopulation in the anterior half of the corneal stroma, without damageto the endothelium. Electron spin resonance demonstrated thatWST11/NIR generates hydroxyl and superoxide radicals but nosinglet oxygen in the cornea. These results, in particular whencombined with additional optical spectroscopy techniques, suggest anovel mechanism for corneal stiffening that has not been so faranticipated in connection with current stiffening approaches.Conclusions: Treatment of rabbit corneas, with thebacteriochlorophyll derivative WST11 and NIR illumination,increased their biomechanical strength through mechanism that doesnot involve singlet oxygen. WST11 in 20% dextran T-500/NIRtreatment showed less adverse effects. This treatment may have apotential for clinical use in keratoconus and corneal ectasia.Commercial Relationships: Arie L. Marcovich, Yeda Researchand Development Company, Weizmann Institute of Science (P);Alexander Brandis, Yeda Research and Development CompanyLtd., Weizmann Institute of Science (P); Ilan Feine, None; Iddo©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.