Measurement of corneal tangent modulus using ultrasound indentation.
Biomechanical properties are potential information for the diagnosis of corneal pathologies. An ultrasound indentation probe consisting of a load cell and a miniature ultrasound transducer as indenter was developed to detect the force-indentation relationship of the cornea. The key idea was to utilize the ultrasound transducer to compress the cornea and to ultrasonically measure the corneal deformation with the eyeball overall displacement compensated. Twelve corneal silicone phantoms were fabricated with different stiffness for the validation of measurement with reference to an extension test. In addition, fifteen fresh porcine eyes were measured by the developed system in vitro. The tangent moduli of the corneal phantoms calculated using the ultrasound indentation data agreed well with the results from the tensile test of the corresponding phantom strips (R(2)=0.96). The mean tangent moduli of the porcine corneas measured by the proposed method were 0.089±0.026MPa at intraocular pressure (IOP) of 15mmHg and 0.220±0.053MPa at IOP of 30mmHg, respectively. The coefficient of variation (CV) and intraclass correlation coefficient (ICC) of tangent modulus were 14.4% and 0.765 at 15mmHg, and 8.6% and 0.870 at 30mmHg, respectively. The preliminary study showed that ultrasound indentation could be applied to the measurement of corneal tangent modulus with good repeatability and improved measurement accuracy compared to conventional surface displacement-based measurement method. The ultrasound indentation can be a potential tool for the corneal biomechanical properties measurement in vivo.
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China.
Li-Ke
LK
Wang
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China.
Yan-Ping
YP
Huang
Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing, China.
Lei
L
Tian
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China; School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China.
Chea-Su
CS
Kee
Interdisciplinary Division of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China. Electronic address: ypzheng@ieee.org.
Yong-Ping
YP
Zheng
D000818:Animals; D001696:Biomechanical Phenomena; D003315:Cornea / Q000000981:diagnostic imaging* / Q000502:physiology*; D055119:Elastic Modulus; D004867:Equipment Design; D007429:Intraocular Pressure; D019047:Phantoms, Imaging; D013552:Swine; D014159:Transducers; D014463:Ultrasonography / Q000379:methods*
Corneal biomechanics; Corneal tangent modulus; Intraocular pressure; Ultrasound indentation