Non-invasive Intraocular Pressure Monitoring Research Articles

Effect of variations of corneal physiology on novel non-invasive intraocular pressure monitoring soft contact lens.

Glaucoma is the leading cause of irreversible blindness around the world. With its slow asymptomatic progression, there is an emphasis on early detection and frequent monitoring. A novel microfluidic contact lens has been established as a potential way to track the fluctuations of the intraocular pressure (IOP) which is a key indicator for diagnosing and monitoring glaucoma progression. The purpose of this article is to determine the effect of physiological variations of the eye on the performance of the microfluidic contact lens. Ultrasound biomicroscopy (UBM) was used to measure the central corneal thickness (CCT) and radius of corneal curvature (RCC) for a series of 16 fresh enucleated porcine eyes. The effect of these corneal anatomic features on device performance was then assessed by systematically adjusting intraocular pressure from 10 to 34mmHg and monitoring the device indicator response. The performance of the microfluidic contact lens was determined by finding the amount the indicator fluid shifted in position as a result of 1 mmHg IOP increase. The relationship between IOP and indicator fluid was found to be linear for all eyes. The slope of the indicator fluid movement as a result of the IOP was evaluated against the CCT and RCC of each porcine eye. This yielded low correlation coefficients, 0.057 for CCT and 0.024 for RCC, meaning that these physiological differences showed no systematic impact on the measurements made with the contact lens.

Non-invasive Intraocular pressure monitoring with contact lens

BackgroundGlaucoma is the second leading cause of blindness in the world and the first leading cause of irreversible vision loss. Currently, the primary methodology of testing for the intraocular pressure...

Highly Transparent and Sensitive Graphene Sensors for Continuous and Non-invasive Intraocular Pressure Monitoring.

Intraocular pressure (IOP) is the prime indicator for the diagnosis and treatment of glaucoma. IOP has circadian rhythm changes and is dependent on body gestures; therefore, a single measurement in the clinic can be misleading for diagnosis. Herein, few-layer graphene is utilized to develop non-invasive sensors with high transparency, sensitivity, linearity, and biocompatibility for 24 h continuous IOP monitoring. The graphene Wheatstone bridge consisting of two strain gauges and two compensating resistors is designed to improve the sensitivity and accuracy of IOP measurement. Testing results on a silicone eyeball indicate that the output voltage of the sensor is proportional to the IOP fluctuation. Under the various ranges and speeds of IOP fluctuation, the sensor exhibits excellent performance of dynamic cycles and step responses with an average sensitivity of 150 μV/mmHg. With the linear relationship, the average relative error between the calibrated IOP and the standard pressure is maintained at about 5%. More than 100 cycles and interval time measurements illustrate that the sensor possesses significant stability, durability, and reliability. Furthermore, a wireless system is designed for the sensor to realize IOP monitoring using a mobile phone. This sensor, with the average transparency of 85% and its ease of fabrication, as well as its portability for continuous IOP monitoring, brings new promise to the diagnosis and treatment of glaucoma.

High resolution non-invasive intraocular pressure monitoring by use of graphene woven fabrics on contact lens

Monitoring intracorporal pressures are important for health care and diagnosis. In this work, a contact lens tonometer employing graphene woven fabrics (GWFs), which indicate great sensibility of resistance to strain, flexibility, stretchability, transparency, and biocompatibility, is proposed for real-time monitoring intraocular pressure (IOP) with high resolution. The mechanical properties of the device during the deformation were analyzed, and the sensitivity of the fabricated device was tested on a mimic human eyeball. In vitro experiments on porcine eyes were executed to test the effectiveness of the device. The change rate of resistance under different IOP was tested. Also, the relationship between the current changes and IOP variation when keeping the voltage constant for different devices was obtained. The contact lens tonometers with GWFs as high-resolution sensing element have shown a promising prospective to realize the low-cost disposable sensing contact lens with lower power.

Microfluidic contact lenses for unpowered, continuous and non-invasive intraocular pressure monitoring

Intraocular pressure (IOP) is a crucial physiological indicator of the visual system and play a key role in the diagnosis and treatment of glaucoma. However, the current handheld single measurement tools for IOP sensing cannot meet the future demands for glaucoma management. Thus, here we present the microfluidic contact lens sensors that could provide unpowered, continuous and non-invasive IOP monitoring. The microfluidic contact lens is comprised of a sensing layer of the micropatterned soft-elastomer and a hard plastic reference layer. The devices use the annular sensing chamber filled with the dyed liquid and a sensing microchannel as the IOP transducer. Resulting from the volume variance of the sensing chamber and caused by the deformation of the sensing layer under pressure, the IOP signal is detected as the displacement change of the dyed liquid’s interface in the sensing channel, and in which, the displacement change can be optically observed by using the smart-phone camera. Based on the silicone rubber model eyeball, the sensing mechanism of the devices with different design parameters (the position of the sensing chambers and the dimension of the sensing channels) are explored by using the theoretical analyses and experimental investigations. The characteristics of these microfluidic contact lens sensors are tested, in which, the maximum sensitivity of the device (with the sensing chamber of 8.5 mm in diameter and the sensing channel of 100 × 40 um in size) can be achieved to 0.708 mm/mmHg in a working range of 0˜40 mmHg. Also, cyclical tests were conducted and indicated that the devices had a good reversibility and Long-term stability. Furthermore, the device (with the sensing chamber of 5.0 mm in diameter and the sensing channel of 150 × 40 um in size) was test on the porcine eyes ex vivo, showing a sensitivity of 0.2832 mm/mmHg in a range of 8˜32 mmHg and, the device had a good reproducibility to its IOP change. This work provides a promising approach for unpowered, continuous and non-invasive monitoring of IOP.

Capacitive contact lens sensor for continuous non-invasive intraocular pressure monitoring

Intraocular pressure (IOP) is a primary indicative factor in the diagnosis and treatment monitoring of glaucoma. Measurement of IOP during conventional single office consultation is insufficient for determination of the pressure peak, and IOP profile is needed for peak determination. A capacitive wearable contact lens sensor for monitoring of the IOP is developed in this study. A curvature-sensitive inductor–capacitor sensor is fabricated and embedded inside a silicone rubber contact lens, such that the curvature of the lens is correlated with the resonance frequency of the sensor. The curvature of the lens is mechanically related to the IOP in the underlying eye such that the IOP can be determined from the resonance frequency of the sensor. To fit human eyes, the sensor was designed to have an outer diameter of 14mm, radius of curvature of 8.5mm, and operates in human IOP range between 5 and 40mmHg. The frequency responses and the ability of the sensor to track IOP cycles were tested. Tests on model silicone eyes and enucleated porcine eyes showed that the sensors have a linearity R>0.997 and a sensitivity >200ppm/mmHg for IOP monitoring. Together with wireless reading circuitry taped around the eye socket, the new contact lens sensor can be used for continuous IOP monitoring in clinics and at home for determination of the peak IOP for use in glaucoma diagnosis and monitoring.

Non-invasive intraocular pressure monitoring with a contact lens engineered with a nanostructured polymeric sensing film

A new prototype of contact lens sensor (CLS) for monitoring the intraocular pressure (IOP) variations in a non-invasive way has been developed. The CLS has as a key element a thin film, comprised of a new all-organic flexible highly piezo-resistive sensor, that is glued to the central hole of a doughnut-shaped hard contact lens. A few CLSs were fabricated and tested with an eye phantom and with enucleated pig eyes by means of applying pressure with a low pressure transducer and recording the electrical changes in the sensor with a portable recorder. The developed CLSs are biocompatible permitting to transmit the changes in cornea curvature induced by the IOP variations, directly to the flexible conducting polymeric sensor embedded in the CL. The electrical response of the CLS to pressure changes reveals a high linearity as well as a good reproducibility having the proper sensitivity to perform continuous monitoring of IOP.