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Biomedical subjects

G L Portney

Publications and source records attributed to G L Portney.

At least 19 recordsLinked to original sources
PubMed1979

Photogrammetry of the optic disc in glaucoma and ocular hypertension with simultaneous stereo photography.

Stereophotogrammetric evaluations of the optic cup were performed for normal, ocular hypertensive, and glaucomatous eyes. Average volume, area, and depth measurements were progressively larger from normal to ocular hypertensive to glaucomatous eyes, although the distributions of individual values exhibited considerable overlap among the three groups. Similar results were obtained for volume, area, and depth asymmetry between each pair of eyes. None of these measurements was able to distinguish accurately between normal and glaucomatous optic cups. However, normal eyes showed a high correlation (r = +0.85) between area and depth of the optic cup, whereas this area/depth relationship was reduced in ocular hypertensives (r = +0.63) and completely broke down for glaucomatous eyes (r = +0.04). Approximately 89% of the glaucomatous eyes and 47% of the ocular hypertensive eyes were beyond the range of normal area/depth correlation values. These findings represent an improvement over most previous attempts to quantitatively differentiate between normal and glaucomatous eyes on the basis of optic disc measurements alone, and support the hypothesis that optic disc damage usually precedes visual field loss in glaucoma. With further technical refinements such as computer image processing, stereophotogrammetry of the optic cup may become a valuable differential diagnostic technique for glaucoma.

Glaucoma↗
PubMed1978

The limitations of kinetic perimetry in early scotoma detection.

When tested by Goldmann kinetic perimetry ten patients with glaucomatous optic disc cupping had no visual field defects, but visual field defects were detected when tested by threshold static perimetry on the Tubingen perimeter. To improve the detection ability of kinetic perimetry, we suggest placing the interisopter spot-checks close together or expanding the central 30 degrees plotting area.

Evaluation Studies as Topic↗
PubMed1977

Tonography and projection perimetry. Relationship according to receiver operating characteristic curves.

Previous large scale tonographic studies revealed a significant overlap of coefficient of outflow (C) values for normal and glaucomatous eyes, but their differential diagnosis rested primarily on tangent screen visual field tests. To determine whether projection perimetry would make a difference in the correlation of outflow coefficients with glaucoma, 434 eyes from normal, ocular hypertensive (those without scotomas but with elevated intraocular pressure) and glaucomatous categories were evaluated. Results support the conclusions of earlier work concerning C value overlap and demonstrate the relatively better specificity of the initial intraocular pressure over one coefficient of outflow (Po/C) in distinguishing normal from glaucomatous eyes. It also shows that ocular hypertensives as a group are no different from glaucoma patients with regard to their aqueous outflow. Tonographic tests are, therefore, useful in identifying those eyes that need to be watched closely for the development of glaucomatous change.

Aqueous Humor↗
PubMed1977

Optic cupping caused by an intracranial aneurysm.

A 51-year-old woman had optic disk cupping from optic nerve compression by an intracranial aneurysm. Slit-lamp stereoscopic examination of the living eye immediately post mortem revealed an optic cup vertically oral, elongated superiorly, and indistinguishable from disk changes seen early in glaucoma. The histopathological changes differed from those in glaucoma by showing no glial atrophy. Instead, the cupping was caused by loss of axons in the prelaminar region of the nerve head and collapse of glial columns.

Axons↗
PubMed1977

Trabeculectomy and postoperative ocular hypertension in secondary angle-closure glaucoma.

I performed trabeculectomies to reduce the introacular pressure to 20 mm Hg or lower, in 56 eyes with medically uncontrollable primary open-angle glaucoma or secondary angle-closure glaucoma. In the former group, I achieved success in 85% of cases, 65% without further antiglaucomatous therapy. In the latter group, 59% obtained a successful result, 41% without additional treatment. The readings of applanation tonometry on the first postsurgical day were compared to those obtained after one year. Although approximately 50% of eyes in both glaucoma categories had an initially elevated pressure after trabeculectomy, it decreased steadily in most of those with primary open-angle glaucoma. In the secondary angle closure glaucoma population, this immediate postoperative ocular hypertension was significantly correlated with eventual failure of the operation.

Evaluation Studies as Topic↗
PubMed1976

A comparison of four projection perimeters.

Identical specifications for size and luminance of the target and dome on four projection perimeters-Goldmann, Marco, Topcon, and Rodenstock- seemed to indicate that similar visual fields should be plottable with each instrument. We subjected 30 eyes to perimetry with all four machines. The Rodenstock perimeter was usually unable to map the central field with the I2e target and to identify the presence of most visual field defects. The Goldmann was most capable of demonstrating the presence of existing scotomata and was also able to plot them with the greatest definition. The Topcon was next most sensitive followed closely by the Marco. Analysis of the actual target size and luminance on each machine showed that significant variation existed and was probably responsible for the visual field differences that we found.

Clinical Competence↗
PubMed1975

Photogrammetric analysis of volume asymmetry of the optic nerve head cup in normal, hypertensive, and glaucomatous eyes.

Recent studies of optic cup volume, depth, and orifice area demonstrated a large overlap of the range of these factors for normal and glaucomatous eyes, suggesting that it is usually not possible to distinguish abnormal disks on the basis of a particualr set of geometric quantifiers. Because of the knowledge that qualitative asymmetry of a person's optic cups may be a sign of glaucoma, calculation of the quantity of cup asymmetry using the aforementioned geometric parameters was undertaken in 90 patients. Results indicated that 90% of the bilaterally normal subjects who were studied and 80% of the ocular hypertensives had less than 0.20 mm3 cup volume asymmetry. In contrast, however, all of the unilateral glaucoma patients in this sample exceeded that value. It therefore appears that measurement of the amount of, volume asymmetry between a person's optic cups may be a useful tool in the diagnosis of glaucoma.

Adult↗
PubMed1975

The influence of tropicamide on intraocular pressure.

Elevation of intraocular pressure by many cycloplegic drugs has been reported to occur in eyes in which the filtration angle remained open during mydriasis. Tropicamide 1% is also capable of this phenomenon in patients with open angle glaucoma who are being medicated with pilocarpine. However, in normal eyes as well as those with untreated open angle glaucoma, this cycloplegic has a relatively small effect on intraocular pressure. It is postulated that this difference between the subject groups may be due to competitive inhibition of the miotic at the receptor site in those treated with pilocarpine. In 3 patients in whom the intraocular tension elevation was found to be quite marked, heavy pigments showers in the anterior chamber occurred which suggested an outflow obstructive phenomenon similar to that seen in "Pigmentary Glaucoma."

Amides↗
PubMed1975

Ultrasonic localization of choroidal detachment associated with flat anterior chamber.

In postoperative patients with flat anterior chambers and small pupils or dense media, A-scan and B-scan ultrasonography can be useful tools in establishing the proper etiologic diagnosis. By searching for the presence of a choroidal detachment and determining its full location, complete drainage of the suprachoroidal fluid can be accomplished satisfactorily should this form of surgical intervention become necessary. If sufficient evidence of a choroidal detachment is not found, then therapy can be more assuredly directed at relief of pupillary block or reduction of excessive fistulization, other causes of a flat chamber.

Anterior Chamber↗
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↗