Journal of IKEEE (전기전자학회논문지)

Institute of Korean Electrical and Electronics Engineers (한국전기전자학회)
권호 표지
DOI QR코드

DOI QR Code

A Frequency Domain Analysis of Corneal Deformation by Air Puff

Air puff에 의한 각막 변형의 주파수 영역 분석

  • Hwang, Ho-Sik (Dept. of Ophthalmology, Chuncheon Sacred Heart Hospital, Hallym University) ;
  • Lee, Byeong Ha (School of Information & Communications, GIST) ;
  • Lee, Chang Su (Dept. of Electronic Engineering, The University of Suwon)
  • Received : 2014.05.18
  • Accepted : 2014.06.10
  • Published : 2014.06.30
Download PDF
⟨ Previous Next ⟩

Abstract

Intraocular pressure is measured after a cornea air puff by observing biomechanical properties such as thickness or displacement of the cornea. In this paper, we deal with a frequency domain analysis of corneal deformation in the air puff tonometry that is used to diagnose glaucoma or lasik. We distinguish the patient from the normal by measuring the oscillation frequency in the neighborhood of the central cornea section. A binary image was obtained from the video images, and cornea vertical oscillation profile was extracted from the difference between the vertical displacement data and the curve fitting. In terms of Fourier transform, a vibration frequency of 479.2Hz for the patient was obtained as well as more higher 702.8Hz for the normal due to stiffness. Hilbert-Huang transform's empirical mode decomposition generally describes local, nonlinear, and nonstationary data. After the data were decomposed into intrinsic mode functions, a spectrum and power were analysed. Finally, we confirm that the patient has 6 times more higher power ratio for the specific intrinsic mode function between the patient and the normal.

안압의 측정은 각막에 air puff 후 각막의 변형 즉, 각막의 두께나 변위 등 생역학적 성질을 관찰함으로써 이루어진다. 본 논문에서는 녹내장이나 라식의 진단을 위하여 사용되는 안압계의 air puff에 의한 각막의 변형을 주파수 영역에서 분석하였다. Air puff 후 각막의 중심부 주변의 변위에 대한 진동 주파수를 측정함으로써 환자와 정상인을 구별한다. 동영상으로부터 이진 영상을 구하고, 상하 변위 데이터와 곡선 정합의 차를 구하여 시간에 따른 각막 상하 진동 프로파일 데이터를 추출하였다. Fourier 변환으로 비정상인의 진동 주파수는 479.2Hz를 얻었고 정상인의 경우 단단함으로 인하여 702.8Hz의 고주파 성분을 볼 수 있었다. 또한 Hilbert-Huang 변환의 EMD 방법을 이용, 고유 모드 함수로 분해하여 국소적, 비선형, 비정상성을 가지는 데이터를 얻고 주파수와 전력을 분석하였다. 마지막으로 특정 고유 모드 함수에 대한 환자와 정상인의 전력비가 6배 이상 차이가 나는 것을 확인하였다.

Keywords

References

  1. A. Kotecha, "What biomechanical properties of the cornea are relevant for the clinician?" Surv. Ophthalmol. vol. 52, no. 2: pp. 109-114, Nov. 2007. https://doi.org/10.1016/j.survophthal.2007.08.004
  2. S. Kling and S. Marcos, "Contributing factors to corneal deformation in air puff measurements," Ophthalmol. Vis. Sci. vol. 26, no. 54(7) pp. 5078-5085, Jul. 2013. https://doi.org/10.1167/iovs.13-12509
  3. C. Dorronsoro, D. Pascual, P. Perez-Merino, S. Kling, and S. Marcos, "Dynamic OCT measurement of corneal deformation by an air puff in normal and cross-linked corneas," Biomed. Opt. Express. vol. 1, no. 3(3), pp. 473-487 Mar. 2012. https://doi.org/10.1364/BOE.3.000473
  4. Y. Kurita, Y. Iida, R. Kempf, and M. Kaneko, "Dynamic Sensing of Human Eye using a High Speed Camera," Proc. of the 2005 IEEE Internat. Conf. on Information Acquisition pp. 338-343, Jun. 27 - Jul. 3 2005.
  5. K. H. Kim, W. Jang, B. H. Kim, and Y. H. Seo, "Intraocular Pressure Measurement Devices using Micro Reflected Air Pressure Sensor for the Pre-diagnosis of the Glaucoma," Proc. of 10th IEEE Internat. Conf. on Nanotechnology Joint Symposium with Nano Korea KINTEX, Aug. 17-20 2010.
  6. M. R. Bhatt and S. V. Rao, "On Imaging based Non-contact Tonometer for Intraocular Pressure Measurement," 2013 IEEE Point-of-Care Healthcare Technologies (PHT) Bangalore, India, pp. 97-100, Jan. 16-18, 2013.
  7. J. Nishiyama, I. Kao, and M. Kaneko, "IOP Measurement using Air-Puff Tonometry: Dynamic Modeling of Human Eyeball with Experimental Results," Internat. Conf. on Ubiquitous Robots and Ambient Intelligence (URAI), Jeju, pp. 134-139, Oct. 31-Nov. 2 2013.
  8. Y. Yamakoshi, J. Sato, and T. Sato, "Ultrasonic imaging of internal vibration of soft tissue under forced vibration," IEEE Trans. on Ultrasonics, Ferroelectrics and Frequency Control, vol. 37, no. 2, pp. 45-53, 1990. https://doi.org/10.1109/58.46969
  9. W. F. Walker, B. H. Friemel, L. N. Bohs, and G. E. Trahey, "Real-time imaging of tissue vibration using a two-dimensional speckle tracking system," IEEE Proc. on Ultrasonics Symposium, pp. 873-877, 1993.
  10. Z. Xie, E.-H. Kim, and Y. Kim, "Tissue vibration pulsatility for arterial bleeding detection using Doppler ultrasound," IEEE Inter. Conf. on Engineering in Medicine and Biology Society, pp. 2272-2275, 2009.
  11. A. A. Nikooyan, and A. A. Zadpoor, "Effects of Muscle Fatigue on the Ground Reaction Force and Soft-Tissue Vibrations During Running: A Model Study," Biomedical Engineering, IEEE Transactions on vol. 59, no. 3, pp. 797-904, 2012. https://doi.org/10.1109/TBME.2011.2179803
  12. N. E. Huang, and S. S. P. Shen, Hilbert-Huang Transform and its Applications, World Scientific, London, ISBN 978-9812563767, 2005.
  13. R. Ambrosio, "All you have ever wanted to see and measure about Corneal Biomechanics," www.youtube.com/watch?v=lxuOT_23HCA, Apr. 3, 2011.