角膜加振型眼圧計における加振方向に起因した角膜振動形態の変化

<p>In this study, the influence of the direction of the excitation force on the vibration of the cornea is studied by measuring the corneal vibration by changing the installation position of the vibration source of the cornea excitation type tonometer. A cornea excitation type tonometer has been proposed in order to reduce the stress given to a subject. It is a characteristic of this tonometer that the cornea is excited at a frequency below the audible range without contact and the intraocular pressure is estimated from the low-frequency component of the vibration. A point concentration type parametric speaker in which ultrasonic elements are arranged in a curved manner is used as a vibration source, and lowfrequency excitation force is obtained by modulating the carrier wave with a frequency below the audible range. In the results of the previous study, there were some time history response results that the cornea oscillated to pulsate and did not become a steady state. This problem seems to be occurring because the vibration source is installed diagonally with respect to the cornea. Therefore, in this study, we first improved the experimental equipment so that the vibration source and the displacement meter can be placed in front of the cornea. This was realized by performing displacement measurement by OCT. Next, an excitation experiment was carried out when the vibration source was placed in front of the cornea and when the vibration source was arranged diagonally. Experimental results reveal that adequate vibrations cannot be obtained when the vibration source is installed obliquely to the cornea, but good vibration can be obtained when the vibration source is placed in front of the cornea. The results of this study are expected to be useful for improving the accuracy of intraocular pressure estimation of the cornea excitation type tonometer.</p>