Mapping age-related elasticity changes in porcine lenses using bubble-based acoustic radiation force.

Bubble-based acoustic radiation force aims to measure highly localized tissue viscoelastic properties. In the current investigation, acoustic radiation force was applied to laser-induced bubbles to measure age-related changes in the spatial distribution of elastic properties within in vitro porcine lenses. A potential in vivo technique to map lens elasticity is crucial to understanding the onset of presbyopia and develop new treatment options. Bubble-based acoustic radiation force was investigated as a technique to measure the spatial elasticity distribution of the lens in its natural state without disrupting the lens capsule. Laser-induced optical breakdown (LIOB) generated microbubbles in a straight line across the equatorial plane of explanted porcine lenses with 1mm lateral spacing. Optical breakdown occurs when sufficiently high threshold fluence is attained at the focus of femtosecond pulsed lasers, inducing plasma formation and bubble generation. A two-element confocal ultrasonic transducer applied 6.5 ms acoustic radiation force-chirp bursts with the 1.5 MHz outer element while monitoring bubble position within the lens using pulse-echoes with the 7.44 MHz inner element. A cross-correlation method was used to measure bubble displacements and determine exponential time constants of the temporal responses. Maximum bubble displacements are inversely proportional to the local Young's modulus, while time constants are indicative of viscoelastic properties. The apparent spatial elasticity distributions in 41 porcine lenses, ranging from 4 months to 5 years in age, were measured using bubble-based acoustic radiation force. Bubble displacements decrease closer to the porcine lens center, suggesting that the nucleus is stiffer than the cortex. Bubble displacements decrease with increasing lens age, suggesting that porcine lenses become stiffer with age. Bubble-based acoustic radiation force may be well-suited as a potential in vivo technique to spatially map elastic properties of the lens and guide therapeutic procedures aimed at restoring accommodation.

[1]  F JANSSON,et al.  DETERMINATION OF THE VELOCITY OF ULTRASOUND IN THE HUMAN LENS AND VITREOUS , 1962, Acta ophthalmologica.

[2]  E. Mazur,et al.  Minimally disruptive laser-induced breakdown in water. , 1997 .

[3]  B K Pierscionek,et al.  In vitro alteration of human lens curvatures by radial stretching. , 1993, Experimental eye research.

[4]  R F Fisher,et al.  Presbyopia and the changes with age in the human crystalline lens , 1973, The Journal of physiology.

[5]  Gregg E Trahey,et al.  Acoustic radiation force impulse imaging of the mechanical properties of arteries: in vivo and ex vivo results. , 2004, Ultrasound in medicine & biology.

[6]  Matthew O'Donnell,et al.  Bubble-based acoustic radiation force using chirp insonation to reduce standing wave effects. , 2007, Ultrasound in medicine & biology.

[7]  W F Walker,et al.  Internal deformation of a uniform elastic solid by acoustic radiation force. , 1999, The Journal of the Acoustical Society of America.

[8]  Y KIKKAWA,et al.  Elastic properties of the lens. , 1963, Experimental eye research.

[9]  Timothy G. Leighton,et al.  Comparison of the abilities of eight acoustic techniques to detect and size a single bubble , 1996 .

[10]  R. Truscott,et al.  Presbyopia: The First Stage of Nuclear Cataract? , 2006, Ophthalmic Research.

[11]  A. S. Vilupuru,et al.  Optical and biometric relationships of the isolated pig crystalline lens , 2001, Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians.

[12]  R. Fisher.  The elastic constants of the human lens , 1971, Journal of Physiology.

[13]  C Hartung,et al.  Mechanical testing of isolated senile human eye lens nuclei. , 1996, Medical engineering & physics.

[14]  R. Truscott,et al.  Massive increase in the stiffness of the human lens nucleus with age: the basis for presbyopia? , 2004, Molecular vision.

[15]  Holger Lubatschowski,et al.  First safety study of femtosecond laser photodisruption in animal lenses: Tissue morphology and cataractogenesis , 2003, Journal of cataract and refractive surgery.

[16]  R F Fisher,et al.  The force of contraction of the human ciliary muscle during accommodation , 1977, The Journal of physiology.

[17]  Ultrasonic determination of laser manipulated changes in the elastic property of the intraocular lens , 2003, IEEE Symposium on Ultrasonics, 2003.

[18]  Gregg Trahey,et al.  Acoustic radiation force impulse imaging: in vivo demonstration of clinical feasibility. , 2002, Ultrasound in medicine & biology.

[19]  M. O’Donnell,et al.  Spatially mapping the elastic properties of the lens using bubble-based acoustic radiation force , 2005, IEEE Ultrasonics Symposium, 2005..

[20]  W. P. Graebel,et al.  Elasticity of tissues involved in accommodation , 1991, Vision Research.

[21]  J M Thijssen,et al.  Relation between local acoustic parameters and protein distribution in human and porcine eye lenses. , 1994, Experimental eye research.

[22]  R R Krueger,et al.  Experimental increase in accommodative potential after neodymium: yttrium-aluminum-garnet laser photodisruption of paired cadaver lenses. , 2001, Ophthalmology.

[23]  D. Nassiri,et al.  Hardness and ultrasonic characteristics of the human crystalline lens , 2000, Journal of cataract and refractive surgery.

[24]  H. Pau,et al.  The increasing sclerosis of the human lens with age and its relevance to accommodation and presbyopia , 2004, Graefe's Archive for Clinical and Experimental Ophthalmology.

[25]  M. O'Donnell,et al.  Bubble-based acoustic radiation force elasticity imaging , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[26]  W F Walker,et al.  A method of imaging viscoelastic parameters with acoustic radiation force. , 2000, Physics in medicine and biology.

[27]  Holger Lubatschowski,et al.  fs-Laser induced elasticity changes to improve presbyopic lens accommodation , 2005, SPIE BiOS.

[28]  A. Vogel,et al.  Mechanisms of pulsed laser ablation of biological tissues. , 2003, Chemical reviews.

[29]  M. O’Donnell,et al.  Bubble-based acoustic radiation force for monitoring intraocular lens elasticity , 2004, IEEE Ultrasonics Symposium, 2004.

[30]  H. J. Burd,et al.  Can reliable values of Young’s modulus be deduced from Fisher’s (1971) spinning lens measurements? , 2006, Vision Research.

[31]  Henk A Weeber,et al.  Dynamic mechanical properties of human lenses. , 2005, Experimental eye research.

[32]  M. O'Donnell,et al.  Acoustic detection of controlled laser-induced microbubble creation in gelatin , 2005, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[33]  B K Pierscionek,et al.  Age-related response of human lenses to stretching forces. , 1995, Experimental eye research.

[34]  S. Emelianov,et al.  Shear wave elasticity imaging: a new ultrasonic technology of medical diagnostics. , 1998, Ultrasound in medicine & biology.

[35]  J. Longtin,et al.  Modeling optical breakdown in dielectrics during ultrafast laser processing. , 2001, Applied optics.

[36]  G. van der Heijde,et al.  Presbyopia and Velocity of Sound in the Lens , 1994, Optometry and vision science : official publication of the American Academy of Optometry.

[37]  M. Campbell,et al.  Biometric, optical and physical changes in the isolated human crystalline lens with age in relation to presbyopia , 1999, Vision Research.

[38]  G. L. Van Der Heijde,et al.  In vivo determination of the biomechanical properties of the component elements of the accommodation mechanism , 1994, Vision Research.