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Eric R. Mikula, Hui Sun, James Jester, Tibor Juhasz; Measurement of Varying Elasticity Between the Anterior and Posterior Human Cornea With Acoustic Radiation Force Elasticity Microscope. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4200.
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The extensive interweaving of collagen lamellae with Bowman’s layer suggests that the anterior cornea will have different mechanical properties that the posterior stroma. Using the newly developed non-invasive acoustic radiation force elastic microscopy (ARFEM) we show that the anterior cornea is more rigid than the underlying posterior stromal bed in cadaver human corneas.
Corneas human cadaver eyes (San Diego Eye Bank, San Diego California) were excised from the globe leaving a 2 mm scleral rim intact. The corneal samples were suspended in collagen gelatin (10% w/w) within a water tank filled with deionized, degassed water. The water tank was attached to a 3-D mechanical stage allowing for precise control of cavitation bubble placement within the cornea. Femtosecond laser pulses induced optical breakdown and produced cavitation in the anterior and posterior cornea. A confocal ultrasonic transducer applied 6.5 ms acoustic radiation force-chirp bursts to the bubble at 1.5 MHz while monitoring bubble position using pulse-echoes at 20 MHz. A cross-correlation method was used to calculate bubble displacements. Maximum bubble displacements are inversely proportional to the Young’s modulus.
Initial results indicate that the anterior cornea in the human eye is stiffer than the posterior stroma. Initial measurements have shown larger bubble displacements in the anterior cornea, with smaller displacements anteriorly. This indicates a larger Young’s modulus in the anterior cornea in the direction orthogonal to the corneal surface.
Our non-invasive ARFEM results that the anterior cornea is stiffer than the posterior cornea in human cadaver eyes.
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