This paper describes a new method to examine the intraocular pressure (IOP) without any contact to the eye. In our new approach the IOP is determined indirectly from the acoustic properties of the eye as the resonance frequencies of the bulbus are shifting with increasing IOP. Simulations with the Finite Element Method were done to explore the coherence between the IOP and the acoustic properties of the bulbus. A three-dimensional model of the eye was developed comprising the elastic cornea and sclera and the vitreous body. The results showed a significant rise of the resonance-frequencies with increasing IOP. This shift is enlarging for higher modes. In parallel measurements were performed on artificial eyes and on enucleated pig eyes to prove this correlation experimentally. A measuring system existing of a transducer to excite the bulbus, a miniaturized laser-vibrometer and PC was built. The eyes were stimulated both contacting the eye with a transducer by a stick and contactless with sonic waves. Several series of measurements were done to examine the pressure dependency of the acoustic behavior. The measurements showed a proportional constant of 1.25 Hz/mmHg in average, which can be detected easily. The standard deviation measuring different pig eyes was 4.5 mmHg.
This paper was published in SPIE Proceedings Vol. 3564