Assessment of intraocular pressure sensing using an implanted reflective flexible membrane

Abstract

Glaucoma is a neurodegenerative condition that is the leading cause of irreversible blindness worldwide. Elevated intraocular pressure (IOP) is the main cause for the development of the disease. The symptoms of this form, such as deterioration of vision and scotomas (loss of visual fields), appear in the latter stages of the disease. Therefore, an IOP monitoring device is needed for better, simpler, and faster diagnosis, and to enable a fast treatment response. We present a theoretical assessment as well as preliminary experimental results of a simple approach for easy, optical, IOP self-monitoring. It is based on a polydimethylsiloxane membrane coated with a reflective layer and a Hartmann–Shack wavefront sensor. Nearly linear correlation is found between membrane deformation and Zernike coefficients representing defocus primary spherical aberration, with high sensitivity and negligible dependence on the measurement distance. The proposed device is expected to provide an accurate IOP measurement resolution of less than ± 0.2 ?? mm ? Hg with a pressure dependence on working distances < 0.7 ?? mm ? Hg / cm for a thick membrane; the corresponding values for a thin membrane are ± 0.45 ?? mm ? Hg and < 0.6 ?? mm ? Hg / cm , respectively, at typical IOP values—up to 40 mm Hg.

Biocompatible Nanotransfer Printing Based on Water Bridge Formation in Hyaluronic Acid and Its Application to Smart Contact Lenses

“…Previous studies related to smart contact lenses employed various methods, e.g., fabrication of a pattern on a transparent film and its incorporation onto a soft lens, − pattern transfer after photolithography, − laser interference patterning, , and near-field subdiffraction photolithography . The smart lenses resulting from these processes are used for glucose-level measurement, ,,− intraocular pressure measurement, − ,− dry eye prevention, , and color blindness correction. , The process developed in this study was employed to transfer an HA film, nanopatterned with an Al nanoline array, onto a hydrogel-based soft contact lens made of narafilcon A with a water content of 46 wt %. , …”

Effect of optical aberrations on intraocular pressure measurements using a microscale optical implant in ex vivo rabbit eyes

“…The IOP sensor introduced extra aberration due to its flexible surface geometry. 43 The native aberration of the sensors (0.168 AE 0.014 μm) accounts for the increase in the average aberration in Fig. 3(b) (0.514 μm) when compared with that in Fig.…”

“…This trend is consistent with the previous study that showed that the second-order rms-wavefront error originating from a deflected membrane was more sensitive to IOP than the fourth-and higher-order rms-wavefront errors. 43 When the sensors were implanted at three different radial distances from the pupil center in the anterior chamber [Figs. 4(a) and 4(b)], however, the first-order Zernike coefficients became the dominant factor that increased the total rms-wavefront error [ Fig.…”

“…Recently, researchers have developed radio-frequency (RF)-based contact-lens IOP sensors for 24-h monitoring and implantable RF-based sensors for direct IOP and other physiological pressure measurements. In addition, an increasing number of optics-based IOP and other biological pressure monitoring have been demonstrated based on flexible photonic crystal, 34 interferometry, [35][36][37][38][39][40][41][42] aberrometry, 43 microfluidic or micromechanical implants, 44,45 and laser-excited fluorescence. 46 To provide more accurate and frequent IOP monitoring and to improve treatment outcomes, researchers recently demonstrated implantable IOP sensors with remote optical readout in long-term in vivo studies.…”

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

“…However, accurate IOP measurements are highly dependent on patient cooperation and corneal characteristics, such as central corneal thickness (CCT), corneal curvature, hydration, elasticity, hysteresis, and rigidity [5,[9][10][11][12], requiring real-time systems to know the biomechanical properties of the cornea to then compensate in the IOP measurement, such as with the ocular response analyzer (ORA; Reichert Ophthalmic Instruments, Depew).…”