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Biomedical subjects

A H Guerrero

Publications and source records attributed to A H Guerrero.

5 recordsLinked to original sources

Complications of glaucoma drainage implant surgery.

Glaucoma drainage implants play an important role in the management of refractory glaucoma. It may be considered as a primary procedure in eyes with severe scarring of the conjunctiva and the limbus, neovascularization, multiple previous, failed filtering procedures, and severely glaucomatous eyes for which corneal graft is planned. Recommendations have been made regarding improving the biocompatibility of the materials used in the manufacture of these implants. The current state of development of glaucoma drainage implants is likened to that of intraocular lenses in the 1970s. Further development of devices and techniques will only serve to improve our armamentarium and success against glaucoma, specifically refractory glaucoma. Glaucoma posterior tube shunts have proved to be safe, with the majority of complications either nonsight-threatening, spontaneously resolving, or reversible. Considered primarily in the most severe cases of refractory glaucoma, it has otherwise changed the outlook for such patients.

Filtering Surgery↗

Programmed stimulator for threshold of action potential.

A programmed digital stimulator is described, in which the pulse generator can be regulated in frequency and duration. The output pulses amplitude increases automatically by increments under 5% of the previous step, sequence which allows a much better approximation to the threshold value of action potential. A photographic camera is synchronized for recording. The power supplies, pulse duration generator, binary counter, converter, pulse control, and detector circuits are given in detail.

Action Potentials↗

Electronic system for the obtention of phase plane curves for action potentials.

This system is designed for the amplification of the bioelectrical signal, obtention of its derivative in respect to time, automatic brightness control for both beams of the oscilloscope, and stability. The system includes a central measuring section which is a modified Tektronix oscilloscope type 565. Automatic control of brightness as a function of sweeping speed allows photographic recordings.

Action Potentials↗

Automatic microelectrode compensator (AMC).

A solid-state system designed for compensation of asymmetry potentials between microelectrodes, for bioelectric measurements, is described. Advantages over the manual compensator are the following: synchronic compensation of electrodes, application to automatized systems against aging effects in electordes, high speed, and elimination of general muisances of manual circuits. Besides, the system allows to measure digitally the polarization difference and resting membrane potential with precision of +/- 1 mV.

Bioelectric Energy Sources↗