Evaluation of a stereoscopic camera-based three-dimensional viewing workstation for ophthalmic surgery.

PURPOSE: To evaluate the effectiveness of a prototype stereoscopic camera-based viewing system (Digital Microsurgical Workstation, three-dimensional (3D) Vision Systems, Irvine, California, USA) for anterior and posterior segment ophthalmic surgery. DESIGN: Institutional-based prospective study. METHODS: Anterior and posterior segment surgeons performed designated standardized tasks on porcine eyes after training on prosthetic plastic eyes. RESULTS: Both anterior and posterior segment surgeons were able to complete tasks requiring minimal or moderate stereoscopic viewing. The results indicate that the system provides improved ergonomics. Improvements in key viewing performance areas would further enhance the value over a conventional operating microscope. CONCLUSIONS: The performance of the prototype system is not at par with the planned commercial system. With continued development of this technology, the three- dimensional system may be a novel viewing system in ophthalmic surgery with improved ergonomics with respect to traditional microscopic viewing.

Spectrophotometric quantification of bilirubin in hemorrhagic spinal fluid using an innovative algorithm.

Annually, approximately 30,000 people suffer from aneurysmal subarachnoid hemorrhage (SAH) in the United States. In an estimated 5% of these patients, the hemorrhage is difficult to diagnose using conventional methods. Clinicians must rely upon a combination of clinical history, Computerized Tomography (CT) scan evidence and lumbar puncture results to diagnose and differentiate SAH from a traumatic spinal tap (blood in the spinal fluid due to the procedure). Here we describe an algorithm based development of an analytic methodology using visible spectroscopy to reliably quantify bilirubin in hemorrhagic spinal fluid. The analysis, which may be useful for diagnoses concerning hemorrhagic stroke, is based on the detection of bilirubin, and concomitant blood products produced within the Cerebral Spinal Fluid (CSF) following SAH. The algorithm quantifies bilirubin (0.3 to 10 mg/dL) from the resultant absorption spectrum. A model is developed from standard visible spectroscopic absorption curves of bilirubin and hemoglobin by applying traditional Beer's Law principles. The model is coupled to a modified partial least square analysis and control theory concept where the bilirubin is the "signal" and is masked by hemoglobin "noise." This paper describes the computational methods, sensitivity and utility of a system to quantify bilirubin in CSF like solutions containing hemoglobin and bilirubin over 0.5 g/dL-10 g/dL of hemoglobin concentrations.

Miniaturized redox potential probe for in situ environmental monitoring.

The need for accurate, robust in situ microscale monitoring of oxidation-reduction potentials (ORP) is required for continuous soil pore water quality monitoring. We are developing a suite of self-contained microelectrodes that can be used in the environment, such as at Superfund sites, to monitor ORP in contaminated soils and sediments. This paper presents details on our development of microelectrode sensor arrays for ORP measurements. The electrochemical performance of these ORP electrodes was fully characterized by measuring redox potentials in standard solutions. It found that the newly developed integrated ORP microelectrodes produced a very stable voltage response (the corresponding rate of the integrated microelectrode potential change was in the range of 0.6-1.1 mV/min), even when the measurement was carried out outside of a Faraday cage where signals from most conventional microelectrodes are usually inhibited by external electrical nose. These new microelectrodes were easier to fabricate and were more robust than conventional microelectrodes. The tip size of the integrated ORP microelectrode was approximately 200 nm square, with a taper angle of approximately 20 degrees and a length of 57 microm. The integrated ORP microelectrode exhibited better signal stability and substantially shorter response times (from less than a few milliseconds to 30 s, depending on the standard solution used) than the commercial millielectrode (a few minutes). Compared with the slope of the commercial millelectrode, the slope of the integrated microelectrode (61.5 mV/pH) was closerto the ideal slope against quinhydrone calibration solutions. Therefore, it is to be expected that the newly developed ORP microelectrode may have wider applications in contaminated soils, biofilms, and sediments.