Intraocular Pressure Study in Ex Vivo Pig Eyes by the Laser-Induced Cavitation Technique: Toward a Non-Contact Intraocular Pressure Sensor

Abstract

Traditional applanation tonometry techniques lack the necessary accuracy and reliability for measuring the intraocular pressure (IOP), and there is still a need for a reliable technique for in vivo diagnosis. A single laser-induced cavitation bubble event was optically monitored in order to precisely measure the first collapse time of the cavitation bubble, which presents a direct dependence on the liquid pressure. This can certainly be done within the IOP range. We now extend the partial transmittance modulation (STM) technique to determine its feasibility for directly measuring the IOP by studying the nanosecond (ns) pulsed laser-induced cavitation bubble dynamics for an externally pressurized fresh ex vivo porcine eye. The results demonstrate that it is possible to monitor the IOP by detecting the light of a continuous-wave (CW) laser beam which is intensity modulated by the bubble itself. This technique currently presents a measurement resolution of about 4 mmHg in the 5 to 50 mmHg pressure range, indicating the feasibility of this approach for measuring IOP. This technique provides a direct measurement within the anterior eye chamber, avoiding common pitfalls in IOP diagnosis, such as errors due to patient movement, varying physical properties of the eye globe, or central cornea thickness (CCT) effects.

Remote and low-cost intraocular pressure monitoring by deep learning of speckle patterns

“…The device can be made compact, is potentially mobile, and is highly accurate even without preliminary calibration or preliminary information on the tested eye. We succeeded in IOP biomonitoring of 24 eyes of a living creature having characteristics that are closest to the human eye 51,52 , demonstrating high IOP measurement accuracy and potential clinical utility.…”

“…This methodology was tested on artificial eyes as well as on fisheyes. We chose a set of 24 pig eyes for testing for two reasons: they represent a suitable animal model for glaucoma research due to the similarities between the pig eye and the human eye when subjected to chronically increased intraocular pressure; and there is a greater availability of pig eyes compared to nonhuman primate eyes 51,52 .…”

“…For the purpose of demonstrating the feasibility of our method, pig eyes, which are remarkably similar to human eyes, were employed to provide a reliable data collection process with accurate ground truth, and to simulate clinically significant human glaucoma 51,52 .…”

“…The pig eye has become a popular research model due to the ethical and financial constraints involved in employing eyes of other species 51,52 . Pig eyes are very similar to human eyes, having holangiotic retinal vasculature, no tapetum, cone photoreceptors in the outer retina, and similar scleral thickness 53 .…”

“…The method was successfully tested on 24 pig eyeball samples, given their similarity to the human eye 51,52 .…”