Continuous Intraocular Pressure Monitoring Research Articles

Design of a System for Continuous Intraocular Pressure Monitoring

Measuring intraocular pressure (IOP) has proved to be an important diagnosis tool for detecting and preventing glaucoma, a disease that could lead to blindness or even eye loss. Continuous time monitoring of IOP is important for medical research. This paper evaluates the feasibility of two kinds of passive sensors to measure IOP and presents a complete measurement system for one of them.

The changes of vitreous pH values in an acute glaucoma rabbit model.

The changes of vitreous pH values under acute glaucoma status have never been reported. In this study, we measured the changes of vitreous pH values in an acute glaucoma rabbit model. Under ketamine and xylazine anesthesia, the anterior chamber of the right eye of New Zealand white rabbits was cannulated and connected to a polygraph for continuous intraocular pressure (IOP) monitoring and a mini-pump for persistent injection of viscoelastic substance, Healon GV. The measurement of vitreous pH was done by inserting a pH probe via a third opening through the sclera into the vitreous. Different IOP levels were maintained by varied amounts of Healon GV injections into the anterior chamber. The changes of vitreous pH values following the intracameral injections were recorded and evaluated. The changes of vitreous pH values were minimal when IOPs were maintained at lower than 35 mmHg. Vitreous pH values decreased significantly from 7.32 to less than 7.03, when the IOPs were kept at 70 mmHg or higher. However, the decrease of pH values was reversible if IOP was held at 70 mmHg for less than 10 minutes and then reduced to normal level at once. In addition, with MTT viability assay, it was noted that the decrease in vitreous pH was associated with a higher percentage of retinal cell death.

Measurement of intraocular pressure during laparoscopy and its relationship to central venous pressure

STUDY OBJECTIVE. To determine the effect of different positional degrees on hemodynamics, especially central venous pressure and intraocular pressure, and a possible interrelationship, during laparoscopic surgery. SETTING. University teaching hospital (Canadian Task Force classification II-1). Seven women undergoing elective gynecologic laparoscopy. The women were monitored for heart rate, partial pressure of oxygen, end-tidal carbon dioxide, arterial blood pressure, central venous pressure, end-tidal isoflurane concentration, and intraocular pressure in several body positions during general anesthesia. Intraocular pressure depends on body position (r2 = 0.58) related to central venous pressure (r2 = 0.7). Heart rate and arterial blood pressure are also dependent on the body position, but to a lesser degree. Continuous monitoring of intraocular pressure may help detect alterations in central venous pressure during general anesthesia for laparoscopic surgery. Undesirable alterations caused by degree of Trendelenburg position may negatively affect patients with high cardiac or ophthalmic risk.

A system for wireless intra-ocular pressure measurements using a silicon micromachined sensor

A system for the continuous monitoring of intra-ocular pressure is described. The sensor is intended for permanent implantation, integrated with an artificial lens. The system consists of a capacitive pressure sensor, determining the resonance frequency of a passive LC network, and a detector, based on the grid-dip technique. The passive pressure sensing element is micromachined from two silicon wafers and connected to a gold-wire coil. Prototype sensors have been evaluated experimentally in vitro. Pressure has been measured remotely, with promising results.

The IOP-IOL. A probe into the eye.

The intraocular lens (IOL) implant can be looked upon as a probe into the space of the eye. Adapting that view, it is logical to furnish the IOL-probe with biomedical sensors that would explore its environment. A sensor is presented for continuous monitoring of intraocular pressure (IOP), incorporated in the haptics of an IOL. The sensor consists of a capacitative spiral circuit, needing no energy, correlating its resonance frequency to the actual IOP. This resonance frequency is remotely and non-invasively detected by an external device located in a spectacle frame.

Direct Intraoperative Continuous Monitoring of Intraocular Pressure

We present a system of intraoperative continuous monitoring of intraocular pressure (IOP) consisting of a sterilizable pressure sensor attached to a digital monitor and an analogic recording instrument. Used in conjunction with an anterior-chamber maintainer, IOP may be accurately maintained at a specific and desired level.

Passive silicon transensor intended for biomedical, remote pressure monitoring

A sensor is suggested for continuous monitoring of intraocular pressure and similar biomedical applications. The system consists of a capacitive pressure sensor determining the resonance frequency of a passive LC resonator. The resonance frequency is detected in a grid-dip configuration. The paper mainly deals with the capacitive sensor, which is fabricated in silicon, using a silicon fusion bond to seal the cavity. This process will minimize internal stress and provide the necessary conditions for a small temperature drift and stability over long periods of time. Experimentally, prototype sensors have been fabricated and evaluated in vitro. The results are promising and in accordance with theoretical expectations.

Long-term continuous monitoring of intraocular pressure in conscious primates.

A technique for chronic implantation of a device for long-term continuous, quantitative monitoring of intraocular pressure (IOP) in experimental animals is presented. The methodology employed is straight forward and should be easily duplicated for experimental investigations where such monitoring might be useful. Continuous IOP data recorded from the device implanted in a conscious adult rhesus monkey are compared with continuous IOP data reported by other investigators.

A scleral buckle pressure gauge for continuous monitoring of intraocular pressure.

An implantable variable resistance pressure gauge has been constructed from a conductive elastomere in the form of a scleral buckle which is suitable for recording intraocular pressure in vivo continuously over an indefinite period of time. The similarity of the pressure transducer to the standard scleral buckles used to reduce retinal detachments suggests that it will be tolerated over a period of years without significant effect on intraocular pressure. The electrical output from these pressure gauges appears to be both well defined and of sufficient magnitude to operate a valve to control intraocular pressure.