Biomedical subjects

A R Ollie

Publications and source records attributed to A R Ollie.

8 recordsLinked to original sources

PubMed1992

Peripheral visual field testing in glaucoma by automated kinetic perimetry with the Humphrey Field Analyzer.

A Humphrey automated perimeter was used to measure the central 24 degrees of vision with static threshold targets and the peripheral field with two automatic kinetic stimuli in 100 eyes of 100 patients with glaucoma or a suspicion of glaucoma and to compare the additional information gained with the peripheral tests. The peripheral visual field supported the diagnosis made with central field testing in approximately one third of the eyes and added additional diagnostic information in another fourth of the cases. In 4% of patients a normal central field was associated with a glaucomatous peripheral defect. Virtually all peripheral defects were in the nasal quadrant, and the more sensitive isopter uncovered the vast majority of the defects.

Automation↗

PubMed1991

Association of Vistech contrast sensitivity and visual field findings in glaucoma.

Single eye visual fields and contrast sensitivity were assessed in 60 subjects, who were being followed up in a glaucoma clinic for manifest glaucoma or a suspicion of glaucoma because of raised intraocular pressure. The Fieldmaster 5000 (static/kinetic perimeter) was used for the visual fields, and a Vistech wall chart sine wave grating test was used for contrast sensitivity measurements. The subjects were divided into three groups--defect (D), suspect (S) and normal (N)--on the basis of their perimetric findings by subjective grading of 16 perimetric scoring categories for each visual field. The mean Vistech sensitivity levels were not found to be significantly different between the D, S, and N field subgroups at any of the five spatial frequencies provided on the test charts (1.5, 3, 6, 12, and 18 cycles per degree). Complex algorithms combining results from two or more spatial frequencies also failed to yield any significant differences between the groups. Diagnostic sensitivity and specificities relating Vistech contrast sensitivity findings to groups N and D never concomitantly exceeded 60%.

Adult↗

PubMed1989

Accuracy of topographic measurements with the Optic Nerve Head Analyzer.

We used a plastic model of the human eye to study the accuracy with which the Optic Nerve Head Analyzer estimates the surface contour and two-dimensional size of the optic nerve head. Computer-generated contour lines were similar to the actual cross-sectional contour of plastic cups as photographed by scanning electron microscopy. The magnification error of computer-measured cup diameters was inversely related to the axial length of the model. The slope of this relationship was reduced with the use of either refraction or axial length as a correction factor for magnification error. Of the two correction factors, the former provided the closest estimation of the known diameters in the phakic model, while the latter performed better in the aphakic model.

Computer Graphics↗

PubMed1989

Automated kinetic perimetry with two peripheral isopters in glaucoma.

An automated perimeter (Fieldmaster 5000) was used to measure the central 30 degrees of vision with static targets (suprathresholding with quantification of defects) and the peripheral visual field with two kinetic stimuli in 599 eyes of 362 patients with glaucoma or a suspicion of glaucoma. The purpose of the study was to compare the additional information gained by measuring the peripheral visual field with two isopters against the time required for this extra examination. The peripheral visual field supported the diagnosis made by central testing in approximately one fourth of all eyes and added additional diagnostic information in another quarter of the cases. In 7% of the total population, or 11% of eyes with abnormal fields, a normal central field was associated with a glaucomatous peripheral defect. Half of the latter eyes had corresponding glaucomatous optic disc changes. The more sensitive isopter uncovered the vast majority of the peripheral field defects. Measurement of each isopter accounted for 22% of the total testing time.

Automation↗

PubMed1989

Reproducibility of pallor measurements with the optic nerve head analyzer.

One eye each of ten healthy volunteers was tested with the Rodenstock Optic Nerve Head Analyzer on ten separate occasions. A color-coded pallor map was developed for each examination. A color transparency of each pallor map was then obtained from the television monitor of the Optic Nerve Head Analyzer, using a camera mounted on a tripod at a fixed distance from the screen. A color-coded zone within the center of the disc was chosen for each set of ten studies, and the area of this zone was measured by boundary analysis with another computerized image analyzer, the Oasys Image Processor. There was wide intrasubject variation in all ten volunteers, suggesting that the pallor map generated by the Optic Nerve Head Analyzer, when used in the manner described in this paper, is not adequate for following subtle changes in optic nerve head pallor.

Humans↗

PubMed1989

Full threshold versus quantification of defects for visual field testing in glaucoma.

Nineteen glaucoma patients, 17 ocular hypertensives, and 16 normal subjects underwent visual field testing on the Humphrey Field Analyzer using two programs: full threshold (thresholding of all test points with double-crossing technique) and quantification of defects (thresholding only points that deviated more than 6 dB from a presumed normal retinal contour). The purpose of the study was to compare the diagnostic value of information gained by the latter, less time-consuming test with that of the full threshold procedure. The average time requirement per eye was 13 min 11 s for full thresholding and 4 min 22 s for quantification of defects. Of the 104 sets of fields, the diagnosis was at variance in 18. The differences were most often due to shallow defects in otherwise normal fields or shallow defects surrounding deeper scotomas that had been detected by both programs. The shallow defects placed the fields in more advanced diagnostic categories and were all detected with the full threshold technique.

Diagnosis, Computer-Assisted↗

PubMed1988

Peripheral visual field testing by automated kinetic perimetry in glaucoma.

The peripheral visual field was measured with a single kinetic target and the central 30 degrees with static stimuli in 600 eyes of 323 patients with glaucoma and patients suspected of having glaucoma using an automated perimeter (Fieldmaster 5000). The purpose of the study was to compare the additional information gained by the peripheral field testing against the time requirement for this extra procedure. An abnormal peripheral field supported the diagnosis suggested by a central abnormality in 131 eyes (21.8%), while a defect in the peripheral field provided the principal diagnostic information, when the central field was normal or equivocal, in 25 cases (4.2%). Peripheral field measurements accounted for approximately 28% of the total testing time.

Glaucoma↗

PubMed1987

Reproducibility of topographic measurements with the optic nerve head analyzer.

We evaluated the reproducibility of optic nerve head contour mapping by the Optic Nerve Head Analyzer with ten recordings and analyses of one eye each in ten normal volunteers and ten analyses of a single recording in three of the eyes. Reproducibility was good for cup-to-disk ratio and neural rim area. Reproducibility was poor for cup volume, which was inversely related to cup size. Instrument and operator error were low for cup-to-disk ratio and neural rim area, but high for cup volume. Subjective comparisons of contour lines from five recordings of six eyes implied good reproducibility of this measurement.

Glaucoma↗