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Biomedical subjects

G L Portney

Publications and source records attributed to G L Portney.

26 records · Page 2Linked to original sources
PubMedDate not supplied

Automated perimetry: background, instruments and methods.

The goal of automated perimetry is to reduce perimetrist involvement and testing time while maintaining standardized test conditions. Proper calibration of the perimeter background luminance and target intensity is important so that results can be compared between examinations and machines. Three testing procedures may be used alone or in combination: kinetic, threshold static and suprathreshold static perimetry. The Octopus and the Perimetron are fully automated perimeters. The former uses threshold static perimetry while the latter uses kinetic and suprathreshold static perimetry. They are operated by small-sized microprocessors using miniature silicone chip circuitry. They are accurately calibrated, fulfilling the specifications deemed necessary by visual psychophysicists. Although data display and plotting problems still exist, automated perimetry is ready for thorough comparisons with Goldmann and Tübinger manual perimetry.

Computers↗
PubMedDate not supplied

Photogrammetric analysis of the three-dimensional geometry of normal and glaucomatous optic cups.

Using photogrammetrically generated maps and measurements, the geometric configuration of the optic cups from a group of normal, hypertensive, and glaucomatous eyes were analyzed in detail. Six distinct three-dimensional shapes were found to characterize the range of normal cups. These forms closely resemble a cone, a cylinder, a hemisphere, a cone-cylinder, a cone-hemisphere, and a cylinder-hemisphere. A composite picture of glaucomatous change was produced by collating the data obtained from different nerve heads which were thought to represent serial stages of disease. Among the many topographic features identified by this analysis is the early deepening of the optic cup which seems to take place only in disc in which the lamina was not visible before glaucoma began. In cups in which this process has occurred and in those in which the lamina was already exposed during the physiologic state, no further increase in the maximum value of this dimension appears to take place until late in the course of the disease. On the surface of the disc, the pattern of erosion is more vertical than horizontal in direction, creating a vertically oriented ellipse of the cup orifice. Its enlargement occurs in a concentric fashion and usually leads to the disappearance of the superior or inferior disc margins or both before losing the rest of the rim. In spite of the precision with which the optic cup morphology was mapped and measured, the end result still lacks the specificity which could be achieved by actually following the same optic discs while they are undergoing progressive atrophy. Such a study is now underway.

Glaucoma↗