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Biomedical subjects

R J Arnzen

Publications and source records attributed to R J Arnzen.

5 recordsLinked to original sources
PubMed1983

Instantaneous tonometry.

Respiration and arterial pulse cause intraocular pressure to cyclically vary around a mean pressure. Both the respiratory and arterial pulse waves approximate sine waves, and we have represented the IOP cycle as the sum of sinusoidal pressure waves. A rapidly acting tonometer may record any portion of the IOP cycle. We have computed the probability that a single pressure measurement will lie within a given interval around mean IOP and the probability that the mean of several such measurements will lie within a given range of mean pressure. The probability that an IOP estimate will lie in a given range of mean IOP decreases as the IOP cycle amplitude increases but increases as the number of tonometric measurements averaged together increases.

Humans↗
PubMed1982

Multiplexed time-lapse photomicrography of cultured cells.

A system of cinemicrography has been developed in which a single microscope and 16 mm camera are multiplexed to produce a time-lapse photographic record of many fields simultaneously. The field coordinates and focus are selected via a control console and entered into the memory of a dedicated microcomputer; they are then automatically recalled in sequence, thus permitting the photographing of additional fields in the interval between exposures of any given field. Sequential exposures of each field are isolated in separate sections of the film by means of a specially designed random-access camera that is also controlled by the microcomputer. The need to unscramble frames is thereby avoided, and the developed film can be directly analysed.

Animals↗
PubMed1981

Constant-area applanation tonography.

A tonography device, based on the MacKay-Marg tonometer, has been constructed which will applanate the cornea to a preselected area of 5.0 to 6.0 mm diameter and maintain that applanation area. The pressure decrease with time should resemble the pressure decrease following bolus injection of fluid into the eye. In most cases the pressure decreased in a linear slope, abruptly terminating in a pressure plateau. In most cases, the pressure after 4 min of tonography was lower than preliminary Goldmann applanation pressure.

Calibration↗
PubMed1980

The trabecular mesh: a mathematical analysis.

The corneoscleral trabecular meshwork is a three-dimensional net of diagonally crossing collagenous fiber invested in endothelium. Tension on the mesh should cause it to tend to bow inward and hold Schlemm's canal open. Inward bowing is restrained by attachment of the outer mesh to the corneosclera, by meridional uveal mesh fibers, and by resistance to mesh element crossing to deformation. A lamella of meshwork is analyzed from a geometrical point of view, and it is found that even were the mesh free to assume an inward bowed hyperboloidal shape, the spur movement required to change mesh configuration from that of a cone frustum to hyperboloid would be only 0.047 mm and not readily recognizable gonioscopically.

Collagen↗