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ARTIGO ORIGINAL99Dynamic ultra high speed Scheimpflug imagingfor assessing corneal biomechanical propertiesAvaliação Dinâmica com fotografia de Scheimpflug de altavelocidade para avaliar as propriedades biomecânicas da córneaRenato Ambrósio Jr 1,2,3 , Isaac Ramos 1,2 , Allan Luz 2,3 , Fernando Correa Faria 1,2 , Andreas Steinmueller 4 ,Matthias Krug 4 , Michael W. Belin 5 , Cynthia Jane Roberts 6ABSTRACTObjective: To describe a novel technique for clinical characterization of corneal biomechanics using non-invasive dynamic imaging.Methods: Corneal deformation response during non contact tonometry (NCT) is monitored by ultra-high-speed (UHS) photography.The Oculus Corvis ST (Scheimpflug Technology; Wetzlar, Germany) has a UHS Scheimpflug camera, taking over 4,300 frames persecond and of a single 8mm horizontal slit, for monitoring corneal deformation response to NCT. The metered collimated air pulse orpuff has a symmetrical configuration and fixed maximal internal pump pressure of 25 kPa. The bidirectional movement of the cornea inresponse to the air puff is monitored. Results: Measurement time is 30ms, with 140 frames acquired. Advanced algorithms for edgedetection of the front and back corneal contours are applied for every frame. IOP is calculated based on the first applanation moment.Deformation amplitude (DA) is determined as the highest displacement of the apex in the highest concavity (HC) moment. Applanationlength (AL) and corneal velocity (CVel) are recorded during ingoing and outgoing phases. Conclusion: Corneal deformation can bemonitored during non contact tonometry. The parameters generated provide clinical in vivo characterization of corneal biomechanicalproperties in two dimensions, which is relevant for different applications in Ophthalmology.Keywords: Biomechanics; Cornea/physiology; Corneal topography/methods; Tonometry, ocular/methodsRESUMOObjetivo: Descrever uma nova técnica para caracterização clínica das propriedades biomecânicas da córnea, usando sistema deimagem dinâmica não invasivo. Métodos: A resposta de deformação da córnea é monitorada durante tonometria de não contatocom fotografia de Scheimpflug de altíssima velocidade. O Oculus Corvis ST (Scheimpflug Technology; Wetzlar, Germany) apresentauma câmera UHS Scheimpflug que adquire mais que 4.300 fotos por segundo com cobertura de 8mm horizontais para monitorar aresposta de deformação durante a tonometria de não contato por sopro de ar. O pulso de ar é muito bem controlado, apresentandouma configuração simétrica em sua pressão, com máxima pressão da bomba fixa de 25 kPa. O movimento bidirecional da córnea emresposta ao jato de ar é monitorado. Resultados: A medida dura 30ms, com 140 fotos adquiridas. Algorítmos avançados identificamos limites anterior e posterior da córnea em cada imagem. A pressão intraocular (PIO) é calculada com base no primeiro momentode aplanação. A amplitude de deformação é determinada pelo maior deslocamento do ápice, durante o momento de maior concavidade.A extensão da aplanação e velocidade da córnea são medidos nas fases de entrada e saída. Conclusão: A deformação da córneadurante a tonometria de sopro por pulso de ar pode ser monitorada em detalhe com sistema de fotografia de altíssima velocidade.Os parâmetros gerados possibilitam caracterização clínica das propriedades biomecâmicas da córnea em duas dimensões. Taisachados têm relavância para diversas áreas da Oftalmologia.Descritores: Biomecânica; Córnea/fisiologia; Topografia da córnea/métodos; Tanometria ocular/métodos1Instituto de Olhos Renato Ambrósio – Rio de Janeiro (RJ), Brazil;2Rio de Janeiro Corneal Tomography and Biomechanics Study Group – Rio de Janeiro (RJ), Brazil;3Department of Ophthalmology, il;4Oculus GmbH - Wetzlar, Germany;5Ophthalmology, University of Arizona – Tucson, AZ, USA;6Ophthalmology, Department of Biomedical Engineering, The Ohio State University – Columbus, OH, USA.Financial Disclosure(s): Mr. Steinmueller, Mr. Krug are employee of Oculus; Dr. Ambrósio, Dr. Belin and Dr. Roberts are consultants for OculusRecebido para publicação em: 11/4/2012 - Aceito para publicação em: 3/12/2012Rev Bras Oftalmol. 2013; 72 (2): 99-102
100Ambrósio Jr R, Ramos I, Luz A, Faria FC, Steinmueller A, Krug M, Belin MW, Roberts CJINTRODUCTIONFrom central keratometry to corneal topography (frontsurface curvature maps), then into 3-D cornealtomography systems, there was a tremendous evolutionon the diagnostic methods for characterizing corneal shape (1,2) .Biological properties, such as wound healing response andbiomechanics, are essential for determining and maintainingcorneal transparency, as well as geometrical and opticalproperties (3) . Corneal biomechanical behavior is well known toinfluence the development of ectatic diseases (4) , and the resultsof surgery (5) . Also, corneal properties influence intraocularpressure measurements (6) , and also may be an independent riskfactor for glaucomatous neuropathy (7-9) .The assessment of corneal biomechanical properties hasbeen limited to laboratory in vitro studies (4,10) , and to virtualmathematical corneal finite element models (6 11,12) . The OcularResponse Analyzer (ORA, Reichert Inc., Depew, NY), amodified non-contact tonometer (NCT) designed to provide amore accurate measurement of IOP through the understandingof compensation for corneal properties, was the first clinical toolfor assessing in vivo biomechanical properties of the cornea (13) .Other nondestructive methodologies have been described,including radial shearing speckle pattern interferometry (14,15) ,Brillouin optical microscopy (16) , OCT (ocular coherencetomography) (17) , and other forms of dynamic cornealimaging (18,19) .We present the Corvis ST (Scheimpflug Technology), anew NCT system integrated with an ultra-high-speed (UHS)Scheimpflug camera that was recently introduced by Oculus(Wetzlar, Germany).Figure 1: Oculus Corvis ST (Wetzlar, Germany)METHODSThe instrument has an ergonomic design (Figure 1), withadjustable head console and chin rest. The patient is comfortablypositioned with proper placement of the chin and forehead. Thepatient is asked to focus at the central red LED (Light EmittingDiodes). A frontal view camera is mounted with a keratometertypeprojection system for focusing and aligning the corneal apex.The exam is programmed for automatic release when alignmentis achieved with the first Purkinje reflex of the cornea. Manualrelease is also possible.The UHS Scheimpflug camera takes over 4,300 frames persecond to monitor corneal response to a metered collimated airpuff with fixed profile that has symmetrical configuration andfixed maximal internal pump pressure of 25 kPa (Figure 2). TheUHS Scheimpflug camera has blue light LED (455 nm, UV free)and covers 8.5mm horizontally of a single slit. Recordingmeasurement time is 30ms, which allows for acquiring 140 digitalframes. Each image has 576 measuring points.This imaging system allows dynamic inspection of the actualdeformation process during NCT. Advanced algorithms for edgedetection of the corneal contours are applied for every frame(Figure 3). The recording starts with the cornea at the naturalconvex shape. The air puff forces the cornea inwards (ingoingphase) through applanation (first or ingoing applanation) into aconcavity phase until it achieves the highest concavity (HC).There is an oscillation period before the outgoing or returningphase. The cornea undergoes a second applanation beforeachieving its natural shape when there is a possible oscillation.The timing and corresponding pressure of the air puff atFigure 2: Graphic presentation of the air pressure (internal) and thecorneal apex signal with detected applanation momentsthe first and second applanations and at the HC moments areidentified. Intraocular pressure (IOP) is calculated based on thetiming of the first applanation event. This initial IOPmeasurement is dependant of corneal resistance. Thedeformation amplitude (DA) is detected as the highestdisplacement of the apex in the HC moment image. The radiusof curvature at highest concavity is recorded. Applanation lengthsRev Bras Oftalmol. 2013; 72 (2): 99-102
Page 1 and 2: Versão impressavol. 72 - nº 2 - M
Page 3 and 4: 80Revista Brasileira de Oftalmologi
Page 5 and 6: 82108 Efeitos de algumas drogas sob
Page 7 and 8: 84Kara-Junior Ninúmeras vezes ante
Page 9 and 10: 86Ambrósio Júnior Raplicação de
Page 11 and 12: 88Monte FQ, Stadtherr NMINTRODUÇÃ
Page 13 and 14: 90Monte FQ, Stadtherr NMFigura 1AFi
Page 15 and 16: 92Monte FQ, Stadtherr NMtempo (3) .
Page 17 and 18: 94Monte FQ, Stadtherr NM11. Höffli
Page 19 and 20: 96Grandinetti AA, Dias J, Trautwein
Page 21: 98Grandinetti AA, Dias J, Trautwein
Page 25 and 26: 102Ambrósio Jr R, Ramos I, Luz A,
Page 27 and 28: 104Caballero JCS, Centurion VINTROD
Page 29 and 30: 106Caballero JCS, Centurion VDISCUS
Page 31 and 32: ARTIGO ORIGINALEfeitos de algumas d
Page 33 and 34: 110Almodin J, Almodin F, Almodin E,
Page 35 and 36: 112 ARTIGO ORIGINALFluência do las
Page 37 and 38: 114Lucena AR, Andrade NL, Lucena DR
Page 39 and 40: 116RELATO DE CASOAsymptomatic ocula
Page 41 and 42: 118Freitas LGA, Gabriel LAR, Isaac
Page 43 and 44: 120Ticly FG, Lira RPC, Fulco EAM, V
Page 45 and 46: 122RELATO DE CASOAssociation of mac
Page 47 and 48: 124Tavares RLP, Novelli FJ, Nóbreg
Page 49 and 50: 126Marback EF, Freitas MS, Spínola
Page 51 and 52: 128RELATO DE CASONeurofibromatose t
Page 53 and 54: 130Moraes FS, Santos WEM, Salomão
Page 55 and 56: 132 ARTIGO DE REVISÃOAntifúngicos
Page 57 and 58: 134Müller GG, Kara-José N, Castro
Page 65 and 66: 142 ARTIGO DE REVISÃOImportância
Page 67 and 68: 144Rehder JRCL, Paulino LV, Paulino
Page 69 and 70: 146Rehder JRCL, Paulino LV, Paulino
Page 71 and 72: 148Instruções aos autoresA Revist
Page 73:
150RevistaBrasileira deOftalmologia
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