Smartphone Software Accurately Measures Intraocular Pressure

The COMSOL Multiphysics mobile software may be effective in accurately measuring intraocular pressure (IOP), according to findings published in Engineering Reports. The app is designed to offer in-home monitoring techniques to patients with glaucoma or suspected glaucoma.

Researchers created a computational model to show a relationship between the internal pressure of an object and its acoustic reflection coefficient. The study explains that the model was constructed using computational geometry to simulate an average human eye, including a precorneal tear film layer of 5 μm with artificial boundary layers. Sound waves at a high frequency (>2000 Hz) were produced from a local source modeled as a Gaussian pulse and were reflected off of the center of the cornea to simulate a constant cornea thickness. Frequency domain was established to indicate the IOP value, since IOP could not be explicitly input as a parameter in the software. This simulation led to the creation of a model that allowed a sweep of frequency and porosity and was used to assess the relationship in question.

The results of the simulation confirmed a relationship between IOP and reflection coefficient, showing a positive correlation between the reflection coefficient and the material’s porosity, and thus, its pressure, at driving frequencies of less than 6000 Hz.

The researchers explain that the replica eye used was a latex balloon housed in plastic tubing because of the setup’s ability to retain its geometry with varying levels of pressure, and the sound waves were generated using an iPhone 8 application. The replica eye’s resonant frequency was 11,000 Hz, while the optimal frequency for maximizing reflection was 8000 Hz.

“The results confirm the theoretical pattern, where there is a frequency (11,000 Hz) which represents the resonant frequency of the material and absorption increases to a much higher value than at surrounding frequencies,” the study concludes. “There is also a frequency (8000 Hz) where reflection is maximum, matching theoretical expectations. For these reasons, the results from the initial frequency sweep can be assumed as accurate.” 

Study limitations include the preliminary nature of the findings, suggesting that more experimentation should be done to confirm whether a relationship exists between acoustic reflection coefficient and central corneal thickness, which would allow this method to stand out among competitors. 

Reference

Soanes M, Essa K, Butt H. Testing the viability of measuring intraocular pressure using soundwaves from a smartphone. Engineering Reports. Published online January 20, 2021. doi:10.1002/eng2.12355