Intraocular pressure measurement using surface acoustic wave optical coherence elastography (SAW-OCE)

IOP is a key parameter in glaucoma progression and is estimated using tonometry. No current tonometer is capable of directly measuring IOP, and very few have been studied against live manometry. Goldmann applanation tonometry is considered the gold standard of tonometry. However, this method is known to have significant inaccuracies notably operator error and variation related to corneal thickness. In addition, it often underestimates high IOP due to its flattening-based measurement method.This study presents an surface acoustic wave optical coherence elastography (SAW-OCE)-based approach for accurately measuring IOP. Corneal geometry and biomechanics were obtained through OCT structural imaging and air-pulse-induced wave imaging. IOP was then calculated using an inversion model. The method was evaluated on in situ porcine eye-globes that were artificially controlled IOPs set at 20, 30, and 40 mmHg. Our findings demonstrated that the OCE-based approach provided IOP measurements of 21.8±3.6 mmHg, 33.4±3.5 mmHg, and 45.0±4.7 mmHg, respectively, which are more closely aligned with the IOPs than those obtained from a conventional tonometer, which recorded 8.5 mmHg, 20.6 mmHg, and 29.0 mmHg. Paired t-tests further confirmed that the OCE method provides highly accurate measurements closely matching the artificial IOPs. The elastography-based system appears to be more accurate at higher pressures and this would make it a clinically safer method of IOP estimation.