Design and development of a noninvasive ocular pressure estimator

Abstract

Significance: A snapshot intraocular pressure (IOP) is ineffective in identifying the IOP peak and fluctuation, especially during sleep. Since IOP variability play a significant role in the progression of glaucoma, 34 monitoring the IOP, especially during sleep is essential to capture the dynamic nature of IOP. Purpose: We aimed to design an ocular pressure estimator (OPE) that can reliably and accurately measure the IOP non-invasively over closed eyelid condition. Methods: OPE works on the principle that the external pressure applied by raising the intraocular pressure of the eyeball is transmitted through a compressible septum to the pressure sensor, thus recording the IOP. A fluid-filled pouch with a pressure sensor was placed over a rubber glove mimicking the eyelid (septum), covering the cornea of enucleated goat eyeballs. A pressure controlled setup was connected to a goat cadaver eye which was validated by a rebound tonometer. Cannulation of eyeballs through the lower limbus had the least difference from the control setup values documented using rebound tonometer, compared to cannulation through the optic nerve. Intraocular pressures ranging from 3–30 mmHg was induced, and the outputs recorded using OPE were amplified and recorded for 10 minutes (n=10 eyes). We stratified the randomization of the number of times and the induced pressures. Results: The measurements recorded were found to be linear when measured against an intraocular pressure range of 3–30 mmHg. The device has excellent reliability (Intraclass correlation coefficient 0.998). The repeatability coefficient and coefficient of variations were 4.24 (3.60–4.87) and 8.61% (7.33–9.90), respectively. The overall mean difference ±SD between induced IOP and the OPE was 0.22 ± 3.50 (95% confidence interval: -0.35, 0.79) mmHg across all IOP ranges. Conclusion: OPE offers a promising approach for reliably and accurately measuring IOP and its fluctuation non invasively under condition mimicking closed eye.