The present study aimed to identify vibroacoustic properties associated with intraocular pressure (IOP) changes and to suggest a new way to measure the IOP based on these properties. Ten ex vivo porcine eyeballs were used in this study. Each eyeball was fixated in a central hole of a Styrofoam block, and vibration applied to the Styrofoam block was transmitted to the eyeball. An accelerometer directly attached to the eyeball measured the vibration response. Excitations and measurements were performed for 1 s, and the excitation magnitude was varied for the same signal in repeat measurements. A 30-gauge needle was inserted into the anterior chamber of the eyeball to inject a balanced salt solution, and the height of the bottle was adjusted to adjust the IOP. A tonometer was used under identical conditions to measure the IOP five times, and the mean value was determined for further analyses. The measurements showed that the parameters resonance frequency and change in the magnitude of the vibration response (CMVR) increased with rising IOP values. The CMVR was highly correlated with the IOP (p-value < 0.0001). A linear mixed effects model (LMM) was used as a statistical analysis method. We confirmed that vibroacoustic properties of the eyeball are correlated with IOP changes. It is expected that the CMVR will serve as a new parameter for IOP measurements. Thus, in the future, continuous IOP measurements would be easily performed using the CMVR.
Sound generated by impacts between raindrops and roof panels of vehicles is an important factor on automotive qualities when driving in rainy conditions. Therefore, analytical method to control this phenomenon is necessary. In this research, a theoretical model for predicting characteristics of sound radiation by droplet impacts was proposed. An experiment for measuring forces generated by falling droplets was conducted. The characteristics of the measured forces were investigated in the frequency domain. A measurement on a plate was performed to understand sound radiation formed by droplet impacts. Correlations between acoustic characteristics and properties of the plate were identified. A vibro-acoustic model was developed to analyze the experimental results. Assuming generation of sound sources at each location due to the vibrating plate, radiation of sound fields was theoretically calculated and verified by comparing with the measured results. Under single and multi-layered conditions, influence factors on acoustic properties were investigated based on the model. As a result, by using the proposed model, it is possible to predict acoustic mechanisms of vehicles due to raindrops and make them suitable for specific designs.
Intraocular pressure (IOP) measurement is one of the basic tests performed in ophthalmology and is known to be an important risk factor for the development and progression of glaucoma. Measurement of IOP is important for assessing response to treatment and monitoring the progression
of the disease in glaucoma. In this study, we investigate a method for measuring IOP using the characteristics of vibration propagation generated when the structure is in contact with the eyeball. The response was measured using an accelerometer and a force sensitive resistor to determine
the correlation between the IOP. Experiment was performed using ex-vivo porcine eyes. To control the IOP, a needle of the infusion line connected with the water bottle was inserted into the porcine eyes through the limbus. A cross correlation analysis between the accelerometer and the force
sensitive resistor was performed to derive a vibration factor that indicate the change in IOP. In order to analyze the degree of influence of biological tissues such as the eyelid, silicon was placed between the structure and the eyeball. The Long Short-Term Memory (LSTM) deep learning algorithm
was used to predict IOP based on the vibration factor.
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